CA2214045A1

CA2214045A1 - In-home theater surround sound speaker system

Info

Publication number: CA2214045A1
Application number: CA002214045A
Authority: CA
Inventors: Jerome E. Ruzicka; Hal P. Greenberger; William F. Clack
Original assignee: Individual
Current assignee: REP Investment LLC
Priority date: 1995-09-07
Filing date: 1996-09-06
Publication date: 1997-03-13
Also published as: CN1177433A; AU7106396A; AU698935B2; US5930370A; IL121700A0

Abstract

An apparatus (10) for realistically reproducing sound, particularly for sound based on a stereophonic signal having dialog and effects and associated with an accompanying video image. The apparatus includes a front speaker (20) located in proximity to the video image for providing acoustic output based upon a summation signal of the component left and right (L+R) channels of the audio signal. A rear speaker (26) located to the rear of the viewing area provides acoustic output based upon a difference signal, (L-R) or (R-L), between the left and right channels. Left and right speakers (22 and 24) are located to the respective left and right sides of the viewing area. The left and right channels speakers (22 and 24) reproduce in one embodiment the respective left and right channels of the audio signal and in a second embodiment reproduce a difference signal, (L-BR) or (R-BL), where B is a gain which may vary or may be a value fixed between zero and unity. Output to the left and right speakers (22 and 24) is band limited to substantially filter out frequency components below a predetermined threshold. A bass speaker (18) may also be provided to output the low frequency components of a (L+R) summation signal. The (L+R) summation signal input to the front speaker assists in localizing dialog to the video image. The (L-BR) or (R-BL) difference signal substantially removes dialog sound so that the side and rear speaker output primarily comprises sonic ambience and surround sound effects.
Band limiting the left and right speakers further assists in localizing dialog to the video image. Alternatively, in yet another embodiment, a monophonic signal may be applied to at least one embodiment of the system to enable production of a spatially enhanced surround sound effect.

Description

CA 0221404~ 1997-08-27 W O 97/09851 PCT~US96/14290 IN-HOME 1H~ATER SURROUND SOUND SPEA~3R ~Y~

BACKGROUND OF THE INVENTION
Technical Field This invention relates generally to the reproduction of stereophonic sound, and, more particularly to the reproduction of stereophonic sound associated with a video image so that dialog 5 is localized to the video image and ambience and sound effects are reproduced in a manner that immerses the listener in a realistic, three-dimensional sound field.
Discussion In the past, numerous monophonic and stereophonic sound systems have been developed in an attempt to achieve high fidelity sound reproduction. Initial efforts restricted the 10 concept of high fidelity to reproducing monophonic audio signals. These early efforts focused on producing a speaker enclosure meeting p~lrolllldllce criteria defined by measurable acoustic rh~r~rt-~ristics such as frequency response, distortion, and dynamic range. The speakers inrlnded an enclosure cont~inin~ one or a number of acoustic tr~n~ rers and crossover networks intrn-l,od to reproduce the full frequency range of audibility. As an example of such a multiple tr~n~ lr.or and 15 crossover configuration, a three-way speaker design includes a woofer transducer to reproduce low frequencies, a mid-range transducer to reproduce middle frequencies, and a tweeter transducer to reproduce high frequrnri.-s.
The typical crossover network described above blends the acoustic output of speaker transducers to achieve good tonal balance characterized by a smooth transition in acoustic output from 20 one transducer to another. One way to accomplish this is a symmetrical crossover network that function as a filter to assure the response drop-off of one tr~n~dl~cer as frequency increases through the transition region is a mirror image of the response increase of a companion transducer reproducing the adjacent higher frequency band of sound. Proper impl~om~nt~tion of this design approach requires that the combination of tran~dl-rPrs and crossover networks do not introduce audible artifact (an CA 0221404~ 1997-08-27 W O 97/09851 PCT~US96/14290 ullllaLuldl sound quality) resulting from frequency response irregularities or phase cancellation effects that potentially result from housing a multiplicity of tr~nx~lllcers in one speaker enclosure.
The early ~LL~ L~ at high fidelity through monophonic audio signals and three way crossover nt;Lwolh~ eventually gave way to stereophonic sound reproduction. Early stereophonic S systems employed a pair of i~lPnti~l, spatially di~LlibuLed high-fidelity speakers to reproduce two-ch~nnPl.~ of audio signal. This spatial ~ LlibuLion of two speaker enclosures is f m-l~mPnt~l to the concept of stereo sound reproduction. A stereo image results when the acoustic output from the pair of speakers fuses into a stereo image pc,ceiv~d as a horizontal panvldllla of sound. This panorama of sound creates for the listener a stereo sound image that spans the space between the two speaker 10 locations. A proper stereo perspective results for a listener positioned along an axis between the two speakers and perpPnfii~ r to the plane of the speakers.
Most speakers employed in stereophonic systems project sound in a direct path from the speaker to the listener, referred to as direct-radiation. In an attempt to broaden the stereo image, ~3eCignPrs have employed speaker pairs which radiate a collll~illaLion of direct and reflected sound.
Such a configuration expands the stereo image beyond the space between the two speakers.
Some more cu"~ ,orary stereophonic sound system designs utilize three-piece sub-satellite speaker systems in which a collll~hlaLion of a sub-woofer bass unit and a pair of satellite speakers replaces the pair of conventional full-range speaker enclosures described above. In such three-piece speaker systems, the satellite speakers reproduce a broad spectrum of mid and high frequency sounds, while the bass unit reproduces only very low frequency sounds. Restricting bass reproduction to the sub woofer unit allows the satellite speakers to be of relatively small size compared to tr~tliti~-n~lly large stereo speaker boxes, whose large size is dictated by the large tr~n~ C~r.c and enclosures needed to achieve good bass response. Many cc.~lxl~ prefer this smaller satellite speaker ~ll~elll~:llL over the more traditional pair of full-range speaker enclosures.
The bass unit can be placed out of sight, and the satellite speakers are more easily blended in with the room decor. However, other con~llmPrx still view these somewhat smaller satellite speaker boxes as unsightly and difficult to incorporate in the home setting in an unobtrusive manner.
Despite the illl~ovtlllents in the overall sound quality provided by even the most sophixti~tPd systems, whether a pair of stereo speakers or a three-piece sub-satellite system, many 30 conxnmPnc believe contemporary sound systems lack the sense of sonic realism associated with live sound. Each sound reproduction system, while meeting 4u~ ie1~ive acoustic p~:lr~3llllance criteria relative to frequency response, distortion, and dynamic range, can subjectively evoke a wide range of listener perceptions of sonic realism from a qualitative point of view. Some systems d~ Illil.Pd to sound more realistic have also been found to create a sense of spaciousness in the reproduced CA 0221404~ 1997-08-27 W O 97/09851 PCT~US96/14290 sound. This del~ i "~ ion has provided the basis for extensive developments in the field of acoustics in order to achieve an .onh~nrecl spatial quality to reproduced sound, while avoiding the introduction . of sonic artifact that would detract from the overall sonic experience.
The three-piece sub-satellite speaker system described above extends the concept of ~ 5 spatially distributing speaker components such as a stereo pair of speakers. The concept can be yet further r~trn(1rd by spatially di~llil ulh-g a ~ l number of point sources for reproducing sound in a li.ct~oning envil~,-.u-c-ll to further increase the perceived spaciousness. While adding a multiplicity of spatially distributed point sources of sound can increase the perception of spaciousness, it also can produce an exaggerated~ overblown spatial ~c~e~ldlion that lacks realism. Such ul~ldlu.dl sound 10 reproduction often causes the listener to experience acoustic fatigue. Thus, enh~nred spaciousness must balance with the perceived acoustic realism of the resulting sound field in order to completely satisfy the listener.
This balance is particularly ill~ l in home theater sound systems where the acoustic re4uhcil1clll~ for this application differ from those for sound reproduction of stereo music.
15 The key objectives for a home-theater sound system are to (1) establish a convincing surround sound acoustic ~tmosphPre based on ambience and sound effect audio signals captured in the soundtrack;

(2) m~int~in a stereo image pdno-~na of sound in front of the viewer; and (3) reproduce dialog that remains localized to the video screen for all viewers in the room. In essence, s~ti~f~rtory acoustic pclrollll~lce results when the listener is immersed in a sound field having a three-dimensional spatial 20 quality perceived as ~nth~ntic in relation to the visual presentation on the video screen.
Initial dllC~ to produce home theater sound included placing a pair of traditional speakers on either side of a centrally located video display. Such systems improved upon the sound of speakers inrhl~le~l within the typical television set. However, the pc~r~ Iance of such systems was ~leterminrd to be unacceptable in the marketplace for at least two reasons. First, listeners located off 25 the center line between the two speakers will not localize dialog to the screen (i.e., perceive the dialog to be solely coming from the screen). Dialog is typically recorded equally in both the left and right rh~nnrlc signals. Localization of dialog will be a point equidistant between the two speakers for a listener on the centerline between the speakers. As a listener moves off the center line, he will move closer to one speaker and farther away from the other. Localization of dialog will shift to the direction from which the first arriving signal origin~tt ~. This will be the closest speaker. Dialog collapses to the near speaker as a listener moves off axis. The localization of dialog will be displaced from the location of the video image for off axis listeners, and the illusion that the characters on screen are actually speaking for off axis listeners will be destroyed. Second, a pair of stereo speakers located on either side of the visual display confines the sound field to the space in front of the CA 0221404~ 1997-08-27 W O 97/098Sl PCT~US96/14290 listener, in the plane of the speakers. There is, thus, no sense of immersion -- a sense that sound events occur to the side or behind the listener as well as in front of the listener.
Many systems have been ~l~o$ignr~1 in an attempt to remedy these ~l~fi~ienri~c. Fo}
example, U.S. Patent No. 3,697,692, issued to Hafler, lli.ccllc.ces using ambience-recovery technology.
Hafler utilized the fact that ~u~ ulld sound illr~.l"lalion resides in virtually all stereo audio signals, whether music l~coldillgs or the soundtrack of video program material, and can be recovered.
Recovery results from obtaining the dirre,~.~e signal between the left and right channel (L - R) leaving sllbst~nti~lly only the ambience portion of the signal. This left minus right (L - R) dirr~le,lce signal reproduced by speakers placed in the rear of the lict-oning room provides the recovered 10 surround sound hlr~).".,.~ n Another ~lJ~ iv~ early home-theater sound system added an ~ litinn~l center channel to reproduce a left plus right (L + R) sum signal to improve the quality of dialog sound reproduction. The center channel was combined with rear sulluulld speakers that reproduce a left minus right (L - R) dirr~,ellce signal, similar to the ambience recovery speakers described above.
15 An example of such a system has been developed by Dolby Laboratories under the name DOLBY
SURROUND.
The center speaker for reproducing the (L + R) signal, as embodied in DOLBY
SURROUND systems, hll~ v~d upon the desirable localization effect of dialog for off-axis lict~n~rc.
However, the (L + R) center channel reproduction did not completely solve the problem of 20 displ~rrment between the auditory and visual images for off axis listeners. Those systems still suffer from localization errors for dialog (and other signals encoded in the sum signal) because passive decoding srh~mPc such as DOLBY SURROUND are only capable of achieving a .n~xi~ r~nt channel separation of 3 dB (where z~ cent rh~nnf~lc are defined as center and right, center and left, left and ~u~l~)u~ld, right and surround). A 3 dB difference in level between dialog in the center 25 channel and dialog in the left and right rh:~nn~lc is not ~ufficient to confine localization to the location of the center channel speaker for all li.ctening positions throughout a typical lictening room.
Localization still shifts to the near speaker for off axis listeners. Having dialog collapse to the near speaker is common to all prior art passive decoder systems.
In an alternative ~ oach to DOLBY SURROUND systems, a T-configuration 30 arrangement proposed by U.S. Patent No. 4,612,663, issued to Holbrook, provides surround sound by passively decoding the stereo signals. The T-configuration includes left and right speakers reproducing the respective left and right signals, a third speaker reproducing the difference (L - R) signal position~d midway between and in the plane of the left and right speakers, and a fourth speaker reproducing the difference signal positioned behind the listener. However, this approach fails to CA 0221404~ 1997-08-27 W O 97tO9851 PCT~US96/14290 Illnill~ a rational sonic image in situations where the stereo signal temporarily has predul~lhldl,Lly left or right channel energy and also fails to prevent the perception of dialog rlll~ g from the near left or near right speaker.
Another system using (L - R) and (R - L) difference signals may be found in U.S.Patent No. 5,027,403, issued to Short et al. Short Ai.~cus~es using forward facing left and right r~l~nnPl~ to provide sound output in the direction of the listener. Short also .licclls~s directing (L +
R) bass signals lc:dlwaldly from the general plane of the video viewing area. Short further ~ c~
directing (L - R) and (R - L) signals l~al~aldly or sidewardly from the general vicinity of the video image. However, Short suffers from the disadvantage that all sounds ~ llnl;llg from the speakers 10 emanate from the video image. Such ~ub~ Lially planer sound radiation does not fully provide the ambience and surround sound effect.
Another example of a system having speakers arranged in a generally planer configuration can be found in U.S. Patent No. 4,497,064, issued to Polk. Polk also ~iccn~;s~s al.al.~hlg main left and right speakers and additional sub-speakers, disposed in proximity to the main 15 speakers, to provide the listener with an ~p~n~l~od acoustic image during stereophonic sound reproduction. However, Polk Illnill~;~ill!C specific, limiting system le~luilt;lllt;lll~, in~ ling that the speakers be eq~ t~nt from the listener in order to assure the arrival of sound at the listener within a pre~ erminf d time period. Polk further ~ cll~.ses high pass filtering an inverted version of a main speaker signal for output from the ~o~ile side sub-speaker. The high pass filtering cancels the 20 opposite side main speaker ~O111~)U11~111 which would otherwise reach the ear of the listener on the side which is filtered. However, the high pass filters are not directed to ~nrelling low frequency components to Ill~ ill localization of voice information to a video image. Polk also specifically requires that all system speakers remain located in ~ub~Lanlially the same plane and radiate in the direction of the listener. The system of Polk will also not be able to m~int~in localization of program 25 material equally recorded in the left and right channels to the area centered between the two speakers for off axis listeners. Localization of such signals will shift toward the near speaker for off axis listeners.
Examples of non-planer speaker configurations include U.S Patent No. 4~443,889, issued to Norgaard. Norgaard ~ cu~ the use of a left front speaker and a right front speaker to 30 reproduce the respective left and right charmel stereo signals. Norgaard also discusses the use of a (L - R) dirrt:-~llce signal through a rear speaker to create an ambience signal. However, among other things Norgaard does not consider combining a (L + R) summation signal through a center speaker to better localize dialog to the video image.

CA 0221404~ 1997-08-27 W O 97/09851 PCT~US96/14290 U.S. Patent No. 5,181,247, issued to Holl discusses similar concepts regarding the use of (L - R) and (R - L) difference signals. However, Holl does not teach the use of a single speaker to output a (L + R) ~.. n~lion signal. Nor does Holl suggest b~n~llimhing the signal input to the ambience speakers.
S U.S. Patent No. 4,819,269, issued to Klayman, tliccllc.sPC radiating sound based on a ~unluldLion signal in a limited dispersion pattern and radiating sound based on a difference signal in a wide dispersion pattern. The radiated signals combine acoustically with the intent of improving the stereo sound in the lict~ning area. However, Klayman specifically requires speci~li7P~l, wide dispersion horns or arrays of multiple tran.C-Illrers to achieve the desired effect described. Further, Klayman does not discuss ~ .hl~ling the primary frequency range of vocal energy from the output of any of the spr~k~rc to better localize dialog to the center speaker.
Other ~ul.vulld sound type systems use complex signal processing in an attempt to L~ve the dp~dlell~ separation between each of the left, center, right, and surround rh~nn~lc The most common system of this type in use today is the DOLBY PRO-LOGIC decoding system. This system improves upon solutions to the basic problems of many prior art passive decoding systems previously described. Active electronic circuits are used to decode matrix-enro-lPcl audio signals, introduce time delays, and accomplish steering between ch~nn~lc through auto-gain control circuitry.
However, the hlll)loved ~elrolllldllce requires a ~ul,~idlllially greater expense because DOLBY PRO-LOGIC requires a Illil~ of four separate amplification rh~nnrlc Further, by their very nature, active electronic signal processing systems potentially introduce sonic artifact (an ulllldLuldl sound quality that can destroy the sense of realism) in their response. One such form of artifact in the DOLBY PRO-LOGIC system results from the active steering circuits that vary the amount of adjacent channel signal subtracted from a signal. For example, when dialog is present and it is desired for it to be localized to the center, the center channel signal is subtracted from the left and right channel signals to remove dialog energy from these rh~nn~-1c This variable subtraction is dyn~mic~lly varying channel separation to m~int~in primary loc~li7z~tion in a particular direction. T ict~n~r.c frequently can hear the ambience (which creates ~tm~cphrre in the audio-video ~lrc~ ion) come and go as dialog enters or leaves the scene. The shrinking down and growing back of the ambience that accclll~anies the introduction and cessation of dialog ~lictr~ctc the listener and proves to be a clear disadvantage of this particular active electronics approach to home-theater sound repro~lllrti~n Another drawback to the DOLBY PRO-LOGIC is that it only works properly with encoded program material. Unencoded material, or material that has been degraded in some way can confuse the logic circuits and cause strange, extreme spatial effects to occur when the decoder steers CA 0221404~ 1997-08-27 W O 97/09851 PCT~US96/14290 localization in a way that was not int--n~leA Another major disadvantage of the active DOLBY PRO-LOGIC decoding system includes its high cost to the consumer and its inherent cnmplexity that makes it difficult for the consumer to install and use the system pLu~elly.
More recently, there has been a return to attempt to provide less complex, 5 inexpensive, passive ~ulluulld sound systems. An example of such systems is described in U.S.
Patent No. 5,386,473, issued to Harrisûn. Harrison is directed to the use ûf a lldl~rullller that passively decodes line level stereo television output signals that require further amplification to produce the high level signal l-~C~~,.I,y to drive speakers. The Lldl~rol~llcl receives input left and right channel signals and provides left front, right front, left rear (L - R), right rear (R - L), center 10 (L + R), and sub-woofer rh~nn~l~ Harrison resûrts to ll~rullllhlg low level signals specifically to solve pel.;c~iv~d problems resulting from the use of speakers connected to high level amplifier outputs to obtain a surround sound effect. However, Harrison cites disadvantages in operating a passive surround sound system s~ti~f~rtorily on high level signals. The present invention is directed specifically to using high level signals to provide surround sound while alleviating the problems 15 mPntionrd regarding high level systems ~liicn~$ed in Harrison, such as the expense of high-powered components, balance problems, and the like.
Other recent attempts at passive decoding include the QD-1 Series II decoder m~n-lf~.tnred by Dynaco. The QD-1 Series II decoder receives signals from the stereo amplifier.
The decoder then produces four (or five) signals -- two front speakers, two rear speakers, and an 20 optional center channel speaker. A second, similar decoder is the HTS-1 Decoder m~mlf~rtllred by Chase Technologies. Similar to QD-1, the Chase Decoder receives signals from the amplifier and then gelleldl~ signals for a pair of front and a pair of rear speakers. The Chase Decoder also produces a signal for an optional, amplified center channel speaker.
These latter two passive decoders suffer from two primary disadvantages. First, the 25 resistor network used to produce a (L + R) signal for the center channel dissipates energy thus requiring a stereo amplifier or receiver of sufficiently high power to overcome this energy loss. It is preferable to provide a system in which all speakers of the system are driven by a relatively low-power amplifier, such as is found in a television or a portable boom-box wherein no power is wasted in signal snmming resistor networks. In one of the previous systems, the center channel speaker must be powered in order to generate the desired function of m~int~ining dialog loe~ ti~m at the physical location of the center speaker. Second, because a certain amount of (L + R) signal is fed to the rear surround speakers, artifact can occur in terrns of dialog ~ lg from the rear surround speaker thus disturbing the realism of the intrn-led ambience effect.

CA 0221404~ 1997-08-27 W O 97/09851 PCT~US96/14290 Thus, there remains a need for a home theater surround sound speaker system which operates using relatively simple, passive electronics in order to limit its cost and thus provide a system having mass market appeal at a reasonable cost. Of particular importance in these systems is the desirability that they present a co~ l ambient sound field while ,ll~ lillg dialog localized to 5 the video image for all positions in the li.ctPning and viewing area. The dialog and visual images also p}eferably coincide at the video image and l,lcrc.~bly are not displaced from each other in a direction of a particular speaker.
Further, audio fl~cignPrs have paid ~ul~L~ltial and particular attention to ~lesigning speaker systems which reproduce left and right channel audio signals of a stereophonic signal to create 10 a three-dimensional ~u~loulld sound sonic effect. However, audio ~.ocign~ rs have largely ignored the monophonic sound market. Many cu~ still have monophonic television sets which output only a single monophonic rh~nnPl~ rather than left and right channel components of a stereo signal. This presently relegates the consumer owning a monophonic television to having sound emanate solely from the television set location. In addition, while AM stereo continues to be discussed and may be 15 employed by a few limited stations, the majority of AM broadcasts continue to be monophonic.
Finally, many programs available on television, VCR, cable, satellite, and other stereo audio/video signal delivery systems have monophonic soundtracks.
Some stereo and home theater audio/visual lcC~ivcl~ apply signal processing t~rhniqur~ to the monophonic sound signal to produce .~imnl~trd stereo or an Pnh~nred spatial sound 20 effect. Such signal processing typically involves additional and complex phase shift, filtering, and digital signal processing cil~;uiLl~. The CC~l~u~"cl thus must absorb the expense of l~u~cllashlg such a receiver, a surround sound decoder, or other sound processing electronic device and a suitable n~Lwulh of speakers to achieve a ~imnl~trd stereo or three-dimensional spatial effect from a monophonic audio signal. Therefore, there exists a need to provide a low-cost, system for effectively 25 reproducing monophonic audio signals in a manner that creates a convincing three-dimensional sonic effect.
In addition to the obvious desirability of a home theater surround sound system which provides all of the above-described benefits, a more practical logistical problem exists in home theater systems. Namely, as home theater systems continue to evolve, they typically require an ever 30 increasing number of additional components. Such Culllpoll~llL~ often include active electronic controllers, numerous speakers connections, ancillary control modules, and separate audio system interconnects. This morass of components often confuses the average consumer during in~t~ tinn.
Despite numerous ~L~L~ ,L~ by m~mlf:~rtllrers to make in~t~ tion more user-friendly and to f~r.ilit~tr the in~t~ tion procedure, many users experience difficulties in properly in~t~lling the system. The CA 0221404~ 1997-08-27 most recent aLlc~ u~s to f~rilit~te the inct~ tirtn process have involved color coding the conn.~ctions at the speaker and at the audio signal source in addition to labeling the conn~ction jacks for the user to view, and have provided detailed and complete inct~ tion instructions. For many reasons, these lllC~bUlCS have failed to provide the co~ -- with a ~urrlciclllly easy way to install home theater sound system col.~clly, and many cc ~ are faced with the expense of a profrcci~-n~l inct~ tion Thus, it is further d~ ble to provide a home theater ~u~uulld sound system whichgreatly f~rilitate,c inet~ tic-n so that the cv~ may relatively quickly, easily, and CGllcclly install and operate the system, thus, c~l~h~ g mass market appeal.

OBJECTS OF THE INVENTION
The present invention aclli-,v~, llUIll~ US obje.iliv~i, based on the novel applir~ti-)n of a variety of arolletir design principles and through a novel co...l~ n of ~Aj~rrnt channel sep~ratinn and individual channel O~cla~illg bandwidth.
It is an object of the present invention to create a realistic sound field to ~cc~
15 video plcc~ nc that localizes dialog to the video screen for all lict~nPne ~luuuglluu~ the viewing area while ...~;..I~;..;ug a col..~ ..l sr~io~lc three .~ 1 sound field.
It is a further object of the present invention to provide a low-cost sound reprodnctir,n speaker system that ploduces ,,,.~ movie-theater ~ulluulld sound culll~alablc or su~e.iol to that provided by complex and c~,~ivc active electronic multi-channel :-ulluulld-sound matrix-~rco~ling 20 systems.
It is a further object of the present invention to passively decouple the reproduction of dialog and ambience audio signals to avoid a,lll,it;nce-instability artifact ~C~oc -~d with active cle~llu"ic signal processing and to ensure the ~le~ ;on of a COllVill~;illg ;..l~ g~ on of visual and sonic images.
It is a further object of the present invention to provide cr~riollc sound reprodlletir,n of collv~"~ional audio signal sources, such as two-channel stereo or matrix-~onr-od~d stereo signals, without the need for auxiliary matrix deco-lir~ ele~lollics.
It is a further object of the present invention to provide a sound repro-luc tion speaker system that produces a spatially t~.l.~...~ed ~ulluund sound sonic effect for a monophonic audio signal.
It is a further object of the present invention to provide a speaker system that is relatively simple and straight-forward for the average COI.~ to install and operate, inrhlrling the provision of mistake-free co.. ~ ~I;on by the c~ in a relatively short period of time.

CA 0221404~ 1997-08-27 It is a further object of the present invention to provide a speaker system that connects easily and directly to a stereo television set without the need for an additional audio-video receiver or amplifier.
It is yet a further object of the present invention to provide movie-theater surround S sound at normal home li~t~ning levels using the low wattage power amplifier, or equivalent, available in commercial stereo TV sets.
It is a further object of the present invention to provide a speaker system having an extraordinarily small size and operating principle that inc- -~olalcS ~ i vc satellite speakers which can be placed unobL--lsivcly in the home cllvhvl~ ent without affecting sonic ~clrollll~lce.
SUMMARY OF THE INVENTION
In accordance with the principles of the present invention, a home theater surround sound speaker system reproduces in a novel manner the ~Le-cu~honic audio portion of an audio/video presentation so that dialog is localized to the video image and the viewer is imm.or.~ed in a sound field 15 perceived as ~llth~ntic in relation to the visual image.
In a first preferred embodiment of the present inventiont the passive, unpoweredspeaker system includes a front speaker, a left speaker, a right speaker, and a rear speaker, each speaker receiving an electrical input signal and providing an acoustic output in accordance with the electrical input signal. The front speaker is located in proximity to the video image and provides an 20 acoustic output in accu..l~lce with a left plus right (L + R) :ju~ ~Lion of the left and right ch~nnrl~
of the stereophonic signal, so that dialog localizes to and coincides with the video image. The right and left speakers may be co-planer with the front speaker. but preferably are located between the viewer and the front speaker, and to the left and the right sides of the viewing area, respectively. The speakers provide acoustic output in accordance with the respective left and right stereophonic 25 rh~nn~l~ The rear speaker is located to the rear of the viewing area and provides acoustic output in accordal~ce with a left minus right (L - R) or right minus left (R - L) difference between the stereophonic channel signals. The difference signal substantially filters out dialog and provides the ambience and surround sound audio hlr~ n The left and right channel electrical signal inputs to the respective left and right speakers are band limited to ~ulJ~L~IlLially remove all frequency 30 components below a pre~lPterminp~l threshold frequency. Band limiting insures that dialog is localized to the front speaker, as the filtering substantially removes signal energy in the speech signal range from the left and right channel signals being acoustically reproduced.
In a second plcr~,.lcd embodiment, the passive, unpowered speaker system includes a front speaker, a left speaker, a right speaker, and a rear speaker, each speaker receiving an -CA 0221404~ 1997-08-27 W O 97tO9851 PCTAUS96/14290 11 .

electrical input signal and providing an acoustic output in accordance with the electrical input signal.

The front speaker is located in proximity to the video image and provides an acoustic output in ~ accoLd~lce with a left plus right (L + R) ~,.Ill,,,. .linn of the left and right rh~nnt-lc of the stereophonic signal, so that dialog localizes to and coincides with the video image. The left speaker may be co-S planer with the front speaker, but preferably is located between the viewer and the front speaker, and to the left side of the viewing area. The left speaker provides acoustic output in accordance with an electrical dirrc-cnce input signal, (L - ~'R), for example, where ~ is a gain factor which varies between zero and unity or may be a value fixed between zero and unity. Similarly, the right speaker is preferably located between the viewer and the front speaker, and to the right side of the viewing 10 area. The right speaker provides acoustic output in acco.dallce with a ~lirrclcllce signal, (R - ~L), for example, where ,~ is a gain factor which varies between zero and unity or may be a value fixed between zero and unity. The rear speaker is located to the rear of the viewing area and provides acoustic output in accoldallce with at least one of a left minus right (L - R) or right minus left (R -L) dirrc~cllce between the stereophonic channel signals. Utilizing the difference signal substantially 15 removes the dialog portion of the audio signal, thereby leaving the ambient sounds in the difference signals. In this second preferred embodiment, the difference signals input to the respective left and right speakers may also be optionally band limited to ~"~ lly remove all frequency components below a preclc~ cl threshold frequency. Band limiting the dirrc~c..ce signals sllhst~nti~lly removes the low frequency components in the dirrclcllce signal so that the difference signal may be 20 reproduced using f~reerlingly small, compact speakers.

In a third preferred embodiment, the powered speaker system inrlll~çs a front speaker, a left speaker, a right speaker, and a rear speaker, each speaker receiving an electrical input signal and providing an acoustic output in accordance with the electrical input signal. Active electronics preprocess and amplifies the left and right rh:~nn~lc of the stereophonic signal to provide a left plus 25 right (L + R) ~ icn signal and a dirrclellce signal, (L - R), for example. The resultant ....,....i.lion and difference signals drive the individual speakers of the speaker system. The front speaker is located in proximity to the video image and provides an acoustic output in accordance with the ~ ~lion signal, so that dialog localizes to and coincides with the video image. The left speaker is located to the left side of the viewing area and provides acoustic output in accordance with the 30 dirrclcllce signal, (L - R), for example. The right speaker is located to the right side of the viewing area, and provides acoustic output in accordance with the difference signal, (R - L), for example.

The rear speaker is located to the rear of the viewing area and provides acoustic output in accordance with the dirrclc~.ce signal. In this third ~lcrc.~cd embodiment, the difference signal may be inverted by reversing the polarity applied to a particular speaker. Also, in this third preferred embodiment, CA 0221404~ 1997-08-27 W O 97/09851 PCT~US96/14290 the difference signals input to the ie~.l e~;Liv~ left and right speakers may be optionally band limited to snbst~nti~lly remove all frequency components below a pre~letPrminPd threshold and enable reproduction of the dir~éiéllce signal using PYeee~lingly small, co~ aeL speakers.
In a fourth preferred embodiment, the system includes a front speaker, a left speaker, 5 a right speaker, and a rear speaker, each speaker receiving an electri~l input signal and providing a monophonic acoustic output in accol~;l~lce with a monnph~nic electric input signal. The front speaker is located in ~ LillliLy to the video image and provides an acoustic output in accold~lce with the monophonic signal. The left speaker may be coplaner with the front speaker, but preferably is located bclwec;l~ the viewer and the front speaker, and to the left of the viewing area. The left 10 speaker provides monophonic acoustic output in accordance with a monophonic electric input signal.
Similarly, the right speaker is plerel~bly located between the viewer and the front speaker, and to the right side of the viewing area. The right speaker provides a monophonic acoustic output in accoL.l~"ce with a monophonic e1Pctri~l input signal. The rear speaker is located to the rear of the viewing area and provides a monophonic acoustic output in accoldd.,ce with a monophonic input 15 signal. Utilizing the monophonic signal enables users having only monophonic audio output sources to obtain an Pnh~n~ed spatial sonic image or a sonic sound effect based upon the monophonic signal.
The monophonic signal input to the respective left and right .cpP~ker.c is band limited, as described herein, to sukst~nti~lly remove all frequency components below a predetPrrninPd threshold frequency.
Band limiting the monophonic signal ~ lly removes the low frequency components in the 20 monophonic signal so that the signal may be reproduced using relatively small, compact satellite speakers. Band limiting also restricts reproduction of the primary vocal energy to the center speaker.
The present invention may also include a power amplifier for receiving left and right input signals and amplifying the left and right input signals for output to the respective speakers. A
powered version having integral amplifiers enables the system designer to generate amplified output 25 signals tailored to the specific speakers selected by the system (1P~ignpr. Such an illlP~ od design approach facilitates oL)li"~ n of the acoustic output of the system.
The present invention further may accommodate an additional bass speaker to reproduce low frequency components of the stereophonic signal. The bass speaker need omy be located generally in the viewing area and provides an acoustic output in accordance with the low 30 frequency components of the (R + L) ~ l ion signal.
The present invention further includes an hlLelco.~l~ect module to facilitate in~t~ tion and operation by the user. The h~Lelco",,ect module includes input and output jacks having a predeterminPd number of termin~l~. The pre~ e, .llil l~d number of tPrmin~l~ in~ tP~ what signals are input or output by the jacks. For example, a three ~ermin~l output jack outputs a left, right and CA 022l404~ 1997-08-27 common ground electrical signal, le~lJe~iliv~ly. Such configuration of the input and output jacks insures proper in~t~ tion of the system because the user may only install the speaker system in one . particular configuration. The speaker system design may include the hllel~;olllle~;L module as an 1iti~n~1, stand-alone component of the system or may incorporate the h~ .;o~llect module circuit with one of the existing culll~ollelll~ such as the bass speaker or the front speaker.
The present invention further includes a wireless impl~ "~ n. In the wireless implPmP-nt~tion, an electrical audio signal connection provides an audio signal to the h"el.;ol,llect module from the audio signal source. The intercormect module inrlll-lec active electronics to produce both difference and ~ on signals. A radio ll,.ll~lllillrl receives the difference signal and 0 Lldll~illli~i the signal. The left, right, and rear speakers each include a radio receiver tuned to the frequency of the L~ l"il~l. The lc.,elvclb thenprovide an amplified electrical signal suitable for production of an acoustic output by the associated speaker.
From the suhsequent detailed description taken in conjull~;tion with the accolll~allyillg drawings and subjoined claims, other objects and advantages of the present invention will become a~al~llL to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a block diagram of the home theater surround sound speaker system arranged in accordance with the principles of the present invention;
Figure 2 is an e~r~nllef~ block diagram of a first preferred embodiment of the home theater surround sound speaker system of Figure 1;
Figure 3a is an e~r~n-led block diagram of a second preferred embodiment of the home theater surround sound speaker system of Figure 1 in which difference signals are output to the left and right satellite speakers;
Figure 3b is an e~r~n-led block diagram of a variation of a second pl~felled embodiment of the home-theater ~ulloulld sound speaker system of Figure 1 in which the signal subtracted to produce the dirrt;lellce signal is ;.llr..,l,.led prior to subtraction;
Figures 4a and 4b are circuit diagla~ for first and second order, respectively, high pass filters for bandwidth limiting the input signal to the left and right satellite speakers;
Figures 5a and 5b are circuit diagrams for applying a left plus right (L + R) ~u".-~a~ion signal to the center speaker using a single tr:~n.~-illcer and a dual transducer configuration, respectively;

CA 0221404~ 1997-08-27 W O 97/09851 PCTrUS96/14290 Figures 6a and 6b a}e circuit diagrams for applying a left minus right (L - R) difference signal to the rear speaker of the home theater ~ulloulld sound speaker system using single and dual voice coil configurations, respectively;
Figure 7 is an .-Yp~n-lec7 block ~ gr~m of a third pl~r~ d embodiment of the home 5 theater surround sound speaker system in which left and right charmel dirrtlel,ce and ~ lion signals are actively g~-n.or~ted prior to output to the spe~ker.e;
Figure 8 is an eYp~n-lPd block diagram of a fourth preferred embodiment of the home-theater surround sound speaker system in which a monophonic signal is output to each of the spe~kere;
Figure 9 is a wiring diagram for an hlLelcollllect module for the home theater surround sound speaker system used to f~ilit~tl- mistake-free inet~ tinn and operation of the system;
Figure 10 is a block diagram of an z~ .",.liv~ configuration for the home theater surround sound speaker system depicted in Figure l;
Figure 11 is a pel~e.;Live view of an integral sub-woofer bass unit and hlL~l.;o~ ect 15 module;
Figure 12 is a wiring diagram for the home theater ~ulloulld sound speaker system sub-woofer bass unit and integral hlL~l~;ollllect module of Figure 11 used to f:~nilit~te mistake-free iner~ tion and operation of the system; and Figure 13 is a block diagram for a wireless implf nn.-nt~tinn of the home theater 20 surround sound speaker system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description of the preferred embodiments is merely exemplary in nature and not int~n-lefl to limit the invention or its application or uses. In the specification, note should be 25 made that elennPntc having similar structures or functions will be referred to using like referenced nnm.?r~l e .
The emborlim~nte described herein provide several improvements over the prior art and will be (liecneeeA briefly at the outset. First, this invention involves the spacial distribution of several speakers about the li.etening room in order to add to the listener's perception of spaciousness.
30 The spacial distribution in~ln~lec left and right side speakers, a rear speaker, a front (or center) speaker, and a sub-woofer. Second, this invention involves localization of sound radiation patterns to a front or center speaker to create an illusion to the listener that certain sound ~ lec from that speaker. This invention also involves the reproduction of particular sounds to create ambient surround sound throughout the room. Such sound ~lcrtlably ~nn~n~tee from speakers other than the CA 022l404~ l997-08-27 front or center speaker. Third, this invention involves frequency band limiting to elimin~t~ particular acoustic frequencies being produced by the left and right satellite speakers. The band limiting frequency is selected in acc.~ldallce with the desire to ~limin~te vocal energy output from the satellite speakers. Fourth, this invention involves an atypical overlapping of the frequency ranges of the speaker components. Thus, each of the front, rear, and side speakers each have rather broad, overlapping frequency ranges. Fifth, this invention passively outputs left rh~nnt-.l, right c.h~nnf~l, left plus right ch:~nn~l, and left minus right channel acoustical signals using several various means of passively ~cllcl~hlg the signals.
Figure 1 depicts a dia~l,.,.,...~lic view of the home theater surround sound speaker 10 system (the ~.u~ ulld sound system) 10 arranged in accu~-lallce with the principles of the present invention. The surround sound system 10 inr.l~ s a source of a preferably amplified stereo signal, shown in Figure 1 as television set 12. The stereo audio source may be any of a number of audio signal sources. It should, thus, be noted that the source of a stereo audio signal is represented herein as television 12, but the audio signal source may also be a stereo receiver, a car stereo, a portable comr~rt disk or tape player, a portable boom-box type stereo, or any other source of a stereo signal.
Television 12 outputs an amplified audio signal to i,.Le,.;ol~lect module 14 via a multiconducter cable 16. Multiconducter cable 16 typically in~.hl~l~,.c two conductor pairs for cnnflll~ting the left and right ch~nn~lc of the stereo signal output by television 12 to interconnect module 14. Interconnect module 14 receives the audio signals from television 12 and assembles the 20 component left and right channel signals for selective di~L~ ulion to particular component speakers of the surround sound system 10.
The component speakers typically include a sub-woofer 18 which receives full range left and right signals, but only reproduces the low frequency components of the audio signal.
I~lLclcol~lect module 14 also outputs an audio signal to front center speaker 20. Front center speaker 25 20 receives both the left and right component signals of the stereophonic signal and reproduces the (L + R) ~ on signal. Preferably, front center speaker 20 is located in proximity to television 12 and projects t_e acoustic output of the (L + R) ~ alion signal toward the listener 28.
Interconnect module 14 also outputs the left channel signal to left satellite speaker 22 and right channel signal to right satellite speaker 24. Left satellite speaker 22 and right satellite 30 speaker 24 may be relatively small speakers and need only reproduce mid range and/or high frequency signals. Left and right satellite speakers are preferably oriented so that the primary axis of radiation of the speaker points upward along a vertical axis; however, other orientations of the satellite speakers may also provide s~ti.cf~rtory pc~r~"lll~lce. IllLelcolluect module 14 also outputs an audio signal to rear ambience speaker 26. Rear ambience speaker 26 typically receives an audio CA 0221404~ 1997-08-27 W O 97109851 PCT~US96/14290 signal in the form of a left channel minus right channel (L - R) or a right channel minus left channel (R - L) difference signal. As will become apparent throughout this detailed description, several embodiments of the invention described herein enable interconnect module 14 to generate a variety of signals to be output to left satellite speaker 22, right satellite speaker 24, and/or rear ambience 5 speaker 26. It should be noted at the outset that the term speaker refers to a system for converting electrical input signals to acoustic output signals where the system may include one or a number of ~,lOSSOvt~l networks and/or tr~ncrlnrPrc.
The components described in Figure 1 typically are arranged to oyliu~ e the sullvulld sound effect to enhance the li.ct.-ning ~Ayc;litllce of the viewer 28. The viewer 28 typically faces television 12 which has front center speaker 20 arranged in proximity to television 12 so that center speaker 20 and television 12 radiate their l~ye-;Liv-e audio and video output in the general direction of viewer 28. The left satellite speaker 22 typically is arranged to the left side of viewer 28 while right satellite speaker 24 is arranged to the right side of viewer 28, both satellite speakers typically being located n~min~lly midway between the viewer 28 and television 12. Rear dull~ ~e speaker 26, which collLlibuLes to creating a spacious audio effect, is typically located behind viewer 28. Rear ambience speaker 26 is depicted as a single speaker, but multiple rear speakers 26 may be inrhl-led in the system.
Figure 2 depicts an exp~n~ d block diagram of a preferred embodiment of the present invention. The expanded block diagrams described herein generally include a partial circuit and wiring ~ gr~mc and will be interchangeably referred to accordingly throughout this speciflr~tion as block, circuit, or wiring diagrams. The home theater surround sound speaker system 100 (surround sound system) includes a left side satellite speaker 102 (left side or satellite speaker), right side satellite speaker 104 (right side or satellite speaker), center speaker 106, ~u~loulld or rear speaker 108, and sub-woofer speaker 110. Left channel amplifier 112 outputs an amplified left channel signal which is input to the positive terminal of voice coil 114a of center speaker 106. The negative terrnin~l of voice coil 114a of center speaker 106 c-,n.leuL~ to the negative terminal of left channel ~mplifier 112. Similarly, right channel amplifier 116 outputs an amplified right channel signal which is input to the positive termin~l of voice coil 114b of center speaker 106. The negative terminal of voice coil 114a of center speaker 106 conn~ctc to the negative terrnin~l of right channel amplifier 116.
The left and right channel signals are thus connf ct~d in phase to the two voice coils 114a and 114b of center speaker 106 so that the output of center speaker 106 is the sum of the left and right (referred to herein as L + R) channel signals.
The positive terminal of left channel amplifier 112 also outputs an amplified left channel signal to the positive termin~l of left side speaker 102, through a filter 118. The negative CA 0221404~ 1997-08-27 W O 97/09851 PCT~US96/14290 terTnin~l of left channel amplifier 112 c~nn~ct~ to the negative tennin~l of left side speaker 102.
Similarly, the positive t~rrnin~l of right channel amplifier 116 also outputs an amplified right channel - signal to the positive t~nin~l of right side speaker 104, through a filter 120. The negative terminal of Aght channel amplifier 116 cullue~L~ to the negative t-?rrnin~l of right side speaker 104. Thus, in 5 the embodiment of Figure 2, the amplified left and right channel signals are output to the respective left and right side speakers.
Left side speaker 102 and right side speaker 104 are preferably band limited to reproduce only higher fic-lucl~;ies, as shown using left high pass filterll8 and right high pass filter 120. The use of high pass filters 118 and 120 with the lc~l~e.;Live left and right side speakers 102 and 10 104 limits the acoustic output of left and right side speakers 102 and 104 to high frequencies. As will be described in greater detail with respect to Figures 4a and 4b, such band limiting of satellite speakers 102 and 104 eYrl~ p~ the primary frequency range of vocal energy. The listener, thus, perceives dialog sound to come only from the front speaker 20 located in proximity to the video image. E~xamples of such high pass filters will be described in greater detail with respect to Figure 15 4a and 4b.
The surround sound system 100 also includes a rear speaker 108. The inputs to rear speaker 108 provide a resultant left minus right (L - R) dirrclcnce signal. To effect this difference signal, the positive t~rmin~l of left channel amplifier 112 outputs the amplified left channel signal to the positive t~rmin~l of rear speaker 108, and the positive terrnin~l of right channel amplifier 116 20 outputs the amplified right channel signal to the negative terminal of rear speaker 108. The above-described conn~cti~n~ to rear speaker 108 provides the desired (L - R) difference signal. Rear speaker 108 also includes a potentiometer 109. The potentiometer 109 enables adjustment of the rear speaker acoustic output relative to the output of the other speakers in the system. Such output is typically adjusted in acco-.lance with the proximity of the rear speaker to the listener. It will be 25 recogni7~d by one skilled in the art that a reversed polarity connection to rear speaker 108 provides a (R - L) dirrelcllce signal, rather than a (L - R) difference signal. The polarity of the difference signal radiated by the rear speaker does not signifi~ntly affect the pclrlJlllldllce of the surround sound system 100, and either ~ " .livc may be selected.
Surround sound system 100 further includes a sub-woofer 110. The positive tennin:~l 30 of left channel amplifier 112 outputs the amplified left channel signal to the positive terminal of left sub-woofer speaker 122. The negative termin~l of left channel amplifier 112 connects to the negative terminal of left sub-woofer speaker 122. Similarly, the positive t~nnin~l of right charmel amplifier 116 outputs the amplified right channel speaker to the positive terminal of right sub-woofer speaker 124. The negative tennin~l of right channel amplifier 116 connects to the negative terminal of right CA 0221404~ 1997-08-27 sub-woofer speaker 124. Thus, in the embodiment of Figure 2, the left channel signal drives the left sub-woofer speaker 122 and the right cha~mel signal drives the right sub-woofer speaker 124, respectively. The resultant output of the left and right sub-woofer speakers thus sum acoustically.
It will be understood by one skilled in the art that the center channel speaker 108 could ~lle~ .l ively S operate over a full frequency range, inrlntling the bass range, thereby elimin~ting the sub-woofer.
In an ~llr~ ;ve embodiment to the above-described preferred embodiment, the leftand right amplifiers 112 and 116 could be hllt~l~LLed into the system. For ~Y~mple, left and right channel amplifies 112 and 116, while generally ~ m-od throughout this specifir~fion to be output ~mplifirr.c c~ ly found and inrln-led in the above-m~nti~ nr-l audio signal sources, may be 10 ~peçifir~lly selected amplifiers forming a portion of ~ullvulld sound system 100. Amplifiers 112 and 116 in this alk;lllalive embodiment would receive low level input signals from the audio signal source.
Amplifiers 112 and 116 would further amplify the input signal for output to the surround sound system sp~ker.c. To effect such a confi~lr~ti-~n, output ~mplifier.~ 112 and 116 may be hlcvll!olaLed into hll~l.;ollllect module 14 (as shown in Figure 1). Illlc;lcvllllect module 14 would pl~r~ably be 15 independently powered to drive amplifiers 112 and 116. A particular advantage of this ~ ",.1;vc~
configuration is that output amplifiers 112 and 116 could be ~ ign.od to specifically integrate with the speaker electrodynamic rl.~l.,c~ ics.
One preferred embodiment of the ~.u~loulld sound system 100 includes a center speaker 106 cvlll~fi~ g a sealed enclosure of approximately 50 cubic inches housing a commercially 20 available 3 inch ~ m~te.r dual 8 ohm voice coil electrodynamic transducer. A pair of 100 micro farad capacitors connected in series with the positive output of the respective left and right channel signals performs a crossover function. The center speaker 106 has an operating bandwidth above ~ xi.,-~l~ly 150 Hz. The rear speaker 108 uses a similar configuration, but uses a single voice coil, rather than a dual voice coil tr~ncd~r~r. The rear speaker 108 includes a sealed enclosure of 25 a~ploxilll,.lely 50 cubic inches and houses a commercially available 3 inch ~ mrter single 8 ohm voice coil electrodynamic tr~n~-ll-rer. Potentiometer 109 is an 8 ohm, 15-watt L-pad or a 25 ohm, 3 watt wh~wuulld potentiometer. Potentiometer 109 allows a variation in the output level of rear speaker 108. A 68 micro farad cdl-a~ or cullllc.;~ed in series with the input to the positive termin~l of the voice coil performs a crossover function. The nominal frequency band of the rear speaker 108 30 is 150 Hz to 8 KHz. The rear speaker 108 reproduces a (L - R) difference signal, as described with respect to Figure 2. The side spl-~ker~ 102 and 104 each comprise a sealed enclosure of v~hllillely 2 cubic inches and houses a cvlllul~lcially available nominal 4 ohm impedance 1.5 inch ~ meter plastic cone tweeter. A pair of 4.7 micro farad ~ a.;ilol~ c-nn~o-cte(l in series with the positive inputs to side speakers 102 and 104 provide high pass filtering for left high pass filter 118 CA 0221404~ 1997-08-27 W O 97/09851 PCT~US96/14290 and right high pass filter 120. The high pass filters 118 and 120 provide a nominal frequency band of approximately 4 KHz to 15 KHz output from side speakers 102 and 104. The sub-woofer 110 is ~ a cu~ lLional dual volume enclosure design comprised of a nominal 580 cubic inch sealed volume and a nominal 450 cubic inch ported volume operating in conjunction with a pair of 5.25 inch ~ 5 ~ el 4 ohm voice coil electrodynamic tr~n~ rer.s. A pair of 0.8 milli-Henry inductors in series with the positive input to each of the ~ -.cd- ~r~J ~7 perform a crossover function. The sub-woofer bass unit 110 nominally operates in the frequency band of 50 Hz to 200 Hz. It should be noted that in each of the above-described speakers, the crossover network is integrated into the enclosure for the associated speaker. Further, it will be noted that the band limiting filters 118 and 120 are integrally 10 inrl~ (l in speakers 102 and 104, respectively. In this manner, the band limiting device and the ~oci~ted satellite speaker form an integral unit. This provides the added benefit that the h~ lect module 14 of Figure 1 may simply be comprised of a~lo~lidt~ly wired input and output jacks.
Figure 3a depicts a second pl~r~lled embodiment of the present invention. The home theater ~,ul~uulld sound speaker system (surround sound system) 200 of Figure 3a employs similar 15 components to those employed in surround sound system 100 of Figure 2, and similar components will be referred to using reference numerals starting with 200 rather than 100. The surround sound system 200 of Figure 3a is as described in Figure 2 except that left side speaker 202 and right side speaker 204 are configured to reproduce .lirr~llce signals (L - R) and (R - L), respectively. The positive t~rrnin~l of left channel amplifier 212 outputs an amplified left channel signal to the positive 20 termin~l of left side speaker 202, via a filter 218. The positive tt-rrnin~l of right channel amplifier 216 outputs an amplified right channel signal connected to the negative terminal of left side speaker 202. Similarly, the positive tel~nin~l of right channel amplifier 216 outputs an amplified right channel signal to the positive termin~l of right side speaker 204, via a filter 220. The positive terminal of left channel ampliher 212 outputs an amplified left channel signal connected to the negative tPrmin~l of 25 right side speaker 204. These connections effect a (L - R) difference signal input to left side speaker 202 and a (R - L) difference signal input to right side speaker 204.
As described with respect to Figure 1, left high pass filter 218 and right high pass filter 220 filter out low frequency components of the input signals applied to left side speaker 202 and right side speaker 204, respectively. In applications where the satellite speakers receive difference 30 signals as inputs, high pass filtering, as described in Figure 2, of the difference signals becomes optional. However, there are two additional benefits to high pass filtering the (L - R) difference signals. First, the physical size of the side speakers can remain small. Second, mi~m~t~h~-~ in the left and right channel signal gains can cause dialog to leak into the difference signal. R~n-llimiting the dirr~nce signal helps ensure that localization of dialog remains at the location of the center -CA 022l404~ l997-08-27 W O 97/09851 PCT~US96/14290 speaker, even when the signals in the left and right ~h~nn~ are not exactly equal and dialog leaks in the difference signal, by filtering out this leakage signal in the primary voice frequency range.
In an ~1t~rn~tive confi~1r~ti~ n of the second, preferred embodiment, reversing the polarity of the difference signals results in a (L - R) difference signal applied to the right side speaker 204 and a (R - L) dirr~;lGllce signal applied to the left side speaker 202. In yet another alternative embodiment, a (L - R) difference signal could be applied to both side speakers 202 and 204, or a (R -L) difference signal could be applied to both side speakers 202 and 204. The particular polarity of the dirr~lence signal applied to the side sre~k~r~ does not materially affect the p~,.ru~ allce of the system when the ;lirr~,~"ce signals are band limited, because the side speakers operate nominally 10 above 1 KHz where the acoustic dirrrl~"ce is inaudible. Further, because the sound signal wavelengths in this frequency range are relatively short, small changes in the relative p1~m~nt of side speakers 202 and 204 will have more of an effect on the way in which signals combine at the 1i~t~-ning position than will the relative polarity of the signals applied to the side speakers.
A particular advantage of driving the left side speaker 202 and right side speaker 204 15 with the difference signal (whether (L - R) or (R - L)) is that the dirr~ ,ce signal removes sound components recorded equally in the left and right ch~nnPl~, rrrr~;Lively decoupling reproduction of dialog and ambient surround sound. Considering a system where the left and right channel signals are output to the ~c~e~;livr left and right side satellite speakers, residual vocal energy harmonics may still reside in the left and right signals at higher frequencies, such as h~r nnni~ overtones, heard as 20 sibilant sounds. When such sibilant sounds are reproduced by the satellite speakers, the satellite ~p.o~k~r.c provide a directional cue that can result in an ~ ".~ 1 breath to the dialog and smear the sonic image. The difference signal, howrvrl, ~1illli.l~1rs these problems by ~oli",i,..l;"g all vestiges of the dialog energy from the ambience surround sound. A further benefit may be obtained by band limiting the difference signal which ~ub~ Lially contains only ambient ~ulluulld sound hlrolllldLion.
Band limiting the difference signal enables use of a much smaller satellite speaker because the satellite speaker need only reproduce high frequency acoustic output. Thus, the c~lll,hldlion of band limiting and the use of difference signals s~lccee~lc in decoupling the reproduction of dialog and ambient sounds, which assures localization of dialog to the video image while .. .~ z.;..i..g a consistent ambient sound field. This decoupling introduces a fim-~m.-nt~1 difference between the passive system of the 30 invention herein and active ~ul~oulld sound decoding systems. The passive system described does not introduce any sonic artifact when dialog comes and goes within an ambient sound field recorded in the so11n-ltr~k Thus, a C(~ ambient sound field results while dialog remains localized to the video screen. The connections for the center speaker, sub woofer, and rear speaker shown in Figure 3a are the same as described with respect to Figure 2. Left channel amplifier 212 outputs an CA 0221404~ 1997-08-27 amplified left channel signal which is input to the positive termin~l of voice coil 214a of center speaker 206. The negative tenninAl of voice coil 214a of center speaker 206 connects to the negative tenninAl of left channel amplifier 212. Similarly, right channel amplifier 216 outputs an amplified right channel signal which is input to the positive tenninAl of voice coil 214b of center speaker 206.
c 5 The negative tenninAl of voice coil 214b of center speaker 206 connects to the ne~dlivc terminaT of right channel amplifier 216. The left and right channel signals are thus colllle~;Lcd in phase to the two voice coils 214a and 214b of center speaker 206 so that the output of center speaker 206 is the left and right ~ ....AIion signals.
Referring again to Figures 2 (and 3), the left side speaker 102 (202) and right side speaker 104 (204) receive the amplified signals output by the left and right channel amplifiers 112 (212) and 116 (216), respectively. However, the operating bandwidth of the side speakers 102 (202) and 104 (204) is restricted. The bandwidth of the side speakers 102 (202) and 104 (204) in the present invention is limited to a frequency range ~ub~Ldlltially above the primary frequency range of voice signals or dialog output by center speaker 106 (206). More particularly, the primary energy 15 in speech signals is c~ A;~d in the frequency range of d~ro~illldLcly 150 Hz to 1 KHz. Side speakers 102 (202) and 104 (204) are bandwidth limited by high pass filters 118 (218) and 120 (220), e~l!e~;~ively, to operate in the frequency range at least above appr~-xim~tPly 1 KHz.
Figure 3b depicts a variation of the second plcrcilcd embodiment of the present invention. The home-theater surround sound speaker system (surround sound speaker system) 200' of Figure 3b employs sirnilar components to those employed in surround sound systems 100 and 200 of Figures 2 and 3a, and similar components to Figures 2 and 3a will be referred to using id~nti~Al reference numerals. The ~ul-oul~d sound system 200' of Figure 3b is as described in Figure 3 except that the left side speaker 202 and right side speaker 204 are configured to produce difference signals (L-,BR) and (R-~L), respectively. As in Figure 3a, the positive terrninAl of left channel amplifier 212 outputs an amplified left channel signal to the positive t~nnin~l of left side speaker 202, via a filter 218. The positive terminal of right channel amplifier 216 outputs an amplified right channel signal c~nn~cted to the negative t~nnin~l of left side speaker 202, via an ~ ol 270. Similarly, the positive t~rmin:~l of right channel :~mplifi~r 216 outputs an amplified right channel signal to a positive t~nnin~l of right side speaker 204, via a filter 220. The positive tenmin~l of left channel amplifier 212 outputs an ~mplifi.-d left channel signal c~ nn~cted to the negative terminal of right side speaker 204, via ~l le~ lor 272.
Att~nll~tors 270 and 272 ~limini~h the subtracted signal prior to input to the negative ~rmin~l~ of the respective side speakers 202 and 204. This results in an output (L-,~R) from left side speaker 202 and (R-~L) from right side speaker 204, where ~ is defined as the gain of the ~rt~m~tors CA 0221404~ 1997-08-27 270 and 272 re~ecLivcly. The gain ~ of the ;1llr~ /ol~ 270 and 272 preferably has a value between zero and unity. Further, as will be untl~n~tood by one skilled in the art, the gain ,l~ of ~ttenll~tors 270 and 272 may be fixed or may be variable, in acculdallce with particular design specifications. In addition, each ~llr~ lur 270 and 272 may optionally provide a dirr~.cll- gain so that ~tt~ml~t-lr 270 5 provides a gain ~l and allr~ 272 provides a gain 1~2 One skilled in the art will easily recognize many various implc...~.l;.lions of ;11lr~ 270 and 272 to provide a gain ~B. For e~mrle, ~mplifier~ 270 and 272 may be implçmented as resistors or potentiometers, in a relatively simple implemPnt~tion. In a more complex implr~ n, a~r.~";"ol 270 and 272 may be implennf~n in any of a number of amplifier configurations known to those skilled in the art.
Figure 4a shows a pair of first order high pass networks to implement the high pass filtering on signals input to left side speaker 102 (202) and right side speaker 104 (204) of Figures 2 and 3. The left high pass filter 118 (218) and right high pass filter 120 (220) include capacitors 150 and 152, le.,l,e~;Liv~ly, colllle~;L~d in series with side speakers 102 (202) and 104 (204). Such a filtering configuration is referred to as a first order high pass filter. Figure 4b dtlllull~lldLes left high pass filter 118 (218) and right high pass filter 120 (220) implem.-ntecl as second order high pass networks. C~p~citors 154 and 156 are connected in series with the positive termin~l~ of side speakers 102 (202) and 104 (204), respectively, and inductor 158 and 160 are connected in shunt across the positive and negative termin~l~ of side spe~kl-r.~ 102 (202) and 104 (204). The operation of the high pass networks depicted in Figures 4a and 4b is well understood by those skilled in the art and will not be eYpl~ined herein.
It will further be recognized by one skilled in the art that high pass filters 118 (218) and 120 (220) may be impl~mente~l in any of a number of configurations known in the art. The use of a passive high pass filter is readily recognized as one a~l!luacll to band limiting signals. It will be further recognized by one skilled in the art that the cut off frequency may be varied in accordance with the particular implement~rion desired.
Bandwidth limiting the frequency range of the signals input to the side speakers 102 (202) and 104 (204) snkst:~nti~lly removes dialog localization cues from the side speakers 102 (202) and 104 (204) so that primary dialog localization cues are only reproduced by the center speaker 106 (206), which is in plo~illli~y to the video image. Bandwidth limiting side speakers 102 (202) and 104 (204) forces dialog localization to the location of the center speaker 106, as the center channel becomes the only speaker in the system that reproduces the filn~l:3m~nf~1 dialog loç~li7~til n cues. The left side speaker 102 (202) and right side speaker 104 (204) reproduce left and right channel higher frequency hlrollllilLion, respectively, that is generally greater than the frequency range of primary speech. The side spezlker.~ 102 (202) and 104 (204), thus, assist in providing an increased sense of -CA 0221404~ 1997-08-27 W O 97/09851 PCT~US96/14290 spaciousness without altering localization of speech sounds. It has been shown through IlUlllclOUS
studies of concert hall acoustics that a sense of spaciousness correlates with the presence of lateral reflections. That is, spaciousness correlates with energy arriving at the li~t~ning position from the sides of the li~t~ning space. Locating the side speakers 102 (202) and 104 (204) at the sides of the S li.~tening room and orienting the major axis of radiation vertically upward enables the side speakers 102 (202) and 104 (204) to gcncldLc .cignificAnt lateral energy at the li.ctening position, thus enhAnring spaciousness. Additionally, because the side speakers 102 (202) and 104 (204) of the present invention are band limited to significantly reduce dialog lo~'Ali7Ation cues, they can be displaced further to the sides of the listener than traditional spe~ker.~. Moreover, because the side speakers 102 (202) and 104 (204) are band limited, the hlcreased displ~r~-n~Pnf does not cause distracting sound images to the sides of the listener, as would occur if full frequency range side speakers were placed in these locations. This allows the side speakers to be placed for ~I~A~ lllll spaciousness without illg distracting sound images.
An additional benefit to band limiting the side speakers is that their physical size may be relatively srnall. Band limiting the side speakers to above a~l~xilll~ly 1 KHz presents a much dirrcrellL configuration than typical satellite/sub-woofer systems. In most satellite/sub-woofer systems, the satellite speakers operate over a much larger frequency range, typically down to as low as 150 Hz. Such speakers are therefore required to be much larger than the side speakers of the present invention in order to generate sllfflcient energy at these lower frequencies. In the present invention, the side speakers reproduce a much more restricted frequency range.
Fig. 5a depicts a center speaker 106 (206) comprised of a dual voice coil 114a and 114b (214a and 214b) and single trAn~ lrer 115 (215) as shown in Figures 2 and 3. The amplified left channel signal is applied to voice coil 114a (214a) and the amplified right channel signal is applied to voice coil 114a (214b). In this configuration, the left and right channel signals are summed electr~lmAgneticAlly within the LlAl~llllr~ 115 (215).
Another particular advantage of this invention can be demonstrated with particular respect to Figure 5a. In Figure Sa, the left and right channel signals output by the respective amplifiers 112 and 116 each individually applied to voice coil 114a and 114b of transducer 115 to electrom~gn~--ticAlly create the (L + R) s--,-----A~ion signal. The center speaker of Figure 5a thus ~;c~craLesthe~.. A~ nsignalpassively,withouttheneedforaresistordividernetworkwhichwould consume power and add cost and complexity to the system. Such power savings is particularly relevant when the invention described herein obtains the left and right channel signals from a relatively low power amplifier source, such as a typical stereo television set or boom-box type CA 0221404~ 1997-08-27 portable stereos. Left plus right ~ inn within the speaker itself avoids the re~lui.clllt;llL for extra parts and their associated costs.
In an alt.-rn~tive center channel confi~lration shown in Figure Sb, the left and right channel signals drive individual left and right tr~ns lllrers 117 and 119 The left channel amplified 5signal drives voice coil 114a (214a) which in turn drives left tr~n.~-11lrer 117. The right charmel amplified signal drives voice coil 114b (214b) which in turn drives trans Inrer 119.
It should be noted that in the confi~lr~tion of Figure 5b, the tr~n~ 7cers 117 and 119 should be located in relatively close proximity so that the outputs from both tr~ns~lllrçrs 117 and 119 sum arollctir~lly over a ~--,-xi--~----~ possible frequency range. Effective acoustical ~ on requires 10 that the two tran~Allrçr.~ be located within alJ~L~-x;~lrly 1/4 of a wavelength of each other. Such o~illliLy is not practically achieved over the entire audible frequency range. At higher freqllpnri~c~
some comb filtering will occur in the combined acoustical output from the two tr~n~lllrl~rs~ In the case of a monophonic signal, because both tr~ns lnr~or.c radiate the same signal and are displaced in space, the resultant path length dirr~lellce between the li~t~ning location and each tr~n~rlnrçr becomes 15 an a~ple~;iable fraction of a wavelength, or multiple wavelengths, at higher frequrnri~. ~iii,ig the spacing between the two elem~nt~, thus, ...i..i.~ S the amount of comb filtering that occurs.
Figure 6 depicts two altt-rn~tive embo-limPnt~ for obtaining (L - R) difference signal from rear speaker 108 (208) of Figures 2 and 3. The dirr~l~llce signal typically contains ambiance and surround sound hlrullllaLion~ Figure 6a depicts a circuit diagram for a preferred embodiment for 20obtaining the (L - R) signal in a passive system. The left channel amplifier 112 (212) outputs an ~mplified left chalmel signal which is input to the positive terminal of voice c oil 130 of the rear speaker 108 (208), and the right channel amplifier 116 (216) outputs an amplified right channel signal to the negative termin~l of voice coil 130. The rear speaker 108 (208), thus outputs audio responsive to the difference between the left and right channel signals (L - R) through transducer 134. Figure 256b depicts a circuit diagram for an ~llrl 1 l;ll i vt~ configuration for obtaining a (L - R) difference signal.
The rear speaker 108 inrl~ s dual voice coils 132a and 132b. Voice coil 132a receives at its positive tçrrnin~l the amplified left channel signal from left channel amplifier 112 (212). The negative terrnin~l of voice coil 132a is connected to the neg~Liv~ terminal of left channel amplifier 112 (212).
Voice coil 132b receives the amplified right channel signal from the right channel amplifier 116 (216) 30at its negative termin~l, and the positive terminal of voice coil 132b connPrt~ to the negative tçr~nin:ll of right channel amplifier 116 (216). Thus, this configuration reverses the polarity of the connection so that tr~n~tlllrrr 134 outputs a resultant (L - R) signal.
Figure 7 depicts a third preferred embodiment of the present invention in which a home theater surround sound speaker system 300 employs low level signal processing prior to CA 0221404~ 1997-08-27 W O 97/09851 PCT~US96/14290 amplification by the amplifier 302 and amplifier 304. Left channel positive signal 306 and right channel positive signal 308 feed into sllmmin~ amplifier 310, any number of said sllmming amplifiers f for electronically adding signals of which are known in the art. The output of sumrning arnplifier 310 provides a (L + R) ~ n signal which is in turn input to power amplifier 302. The positive output of amplifier 302 supplies an amplified (L + R) signal to the positive termin~l of center speaker 312. The negative t~ormin~l of center speaker 312 COnn~~CtC to the negative termin~l of amplifier302.
The positive t-ormin~l of power ~mplifier 302 also outputs a driving signal to the positive termin~l of sub-woofer 314. Sub-woofer 314 cu~ ses a single tr~n~ r-~r and voice coil.
Similarly to center speaker 312, because the (L + R) signal drives sub-woofer 314, sub-woofer 314 ~ uhe~ only a single voice coil and tr~n~-lur~r to output the low r~e~uc~.~ portions of the left and right signals. It will be recognized by one skilled in the art that ~lrern~tive configurations of particular sub-woofers may be used with the present invention with minim~l effect on the functioning of the system.
Surround sound system 300 also actively provides a dirr~ ce signal. Prior to amplification by amplifier 304, left channel positive signal 308 and right channel positive signal 306 feed into dirr~ ce amplifier 316. The output of dirr~.G.., c ~mplifier316 outputs a left minus right (L - R) difference signal. This (L - R) dirr~ ce signal is input to power amplifier 304. The positive output of power amplifier 304 in turn drives the positive termin~l of rear speaker 318. The negative t~rmin~l of rear speaker 318is connected to the negative terrninal of power amplifier 304.
Thus, the (L - R) signal output by amplifier 304 drives rear speaker 318.
The positive termin~l of amplifier 304 also outputs a driving signal to the positive termin~l of left side speaker 320 through high pass filter 324. The negative termin~l of left side speaker 320 connects to the negative t.-rmin~l of power arnplifier 304. Similarly, the positive terminal of power amplifier 304 outputs a driving signal to the negative t~rmin~l of right side speaker 322 through high pass filter 326. The positive terrninal of right side speaker 322 connects to the negative terrnin~l of power arnplifier 304. The connPcfi- n to left side speaker 320 provides a resultant (L -R) driving signal to the speaker. The connection to right side speaker 322 provides a resultant (R -L) signal to the speaker. The polarities of the signals applied to each of left side speaker 320, right side speaker 322, and to rear speaker 318 may be reversed and the system will provide the same effect. All possible permllt~ti-~ns of relative polarity connections of the difference signal to the two side speakers and the rear speaker are also acceptable and provide ~ti~f~rtory results. High pass filters 324 and 326 operate as described above with respect to Figures 2 and 3.
This configuration lends itself particularly to a powered variation in which theh~ ;ol~lect module could include an internal amplifier to amplify the electrical input signals and CA 022l404~ l997-08-27 W O 97/09851 PCT~US96/14290 output amplified ~lectri~l signals to drive the respective speakers. A particularly advantageous feature of an int~rn~lly powered h~L~l~;ol~lect module would be that the option exists to ull~yll~ etrically amplify the output signals so that speakers requiring greater energy to operate s~ti~f~rtorily receive higher powered input signals. For example, the ~,.,,.,..;,1 ion signal input to the 5 center and bass speakers could be output at a much higher power rating than the difference signal output to the satellite and rear ambient speakers. This ~plvacll provides the high power for driving the bass and front speakers while leaving less, but sufficient power to drive the side and rear speakers. For example, rather than a 10-watt plus 10-watt stereo ~mplifitor confiFIlr~tion, an 18-watt plus 2-watt amplifier configuration could be used to more effi~i~ntly employ the available power.
Figure 8 depicts a fourth preferred embodiment of the present invention. The home-theater surround sound speaker system (surround sound system) 400 of Figure 8 employs similar components to those employed in surround sound system 100 of Figure 2, and similar components will be referred to using reference mlm-or~l~ starting with 400 rather than 100. The :,ullvulld system 400 of Figure 8 is configured similarly to Figure 2 except that it receives and outputs a monophonic lS signal rather than component left and right channel signals of a stereo signal. The ~ullvulld sound system 400 inrln-les left side satellite speaker 402 (left side or satellite speaker), right side satellite speaker 404 (right side or satellite speaker), center speaker 406, surround or rear speaker 408, and sub-woofer speaker 410. Amplifier 412 receives a monophonic signal and outputs an amplified monophonic signal which is input to the positive termin~l of voice coil 414 of center speaker 406.
The negative trrTnin~l of voice coil 414 of center speaker 406 connects to the negative termin~l of amplifier 414. Voice coil 414 of center speaker 406 drives tr~n~ -cer 415 to output sound from the center speaker 406. The positive terminal of amplifier 412 also outputs an amplified signal to the positive termin~l of left side speaker 402, through filter 418, and right side speaker 404, through filter 420. Left side speaker 402 and right side speaker 404 are band limited to reproduce only higher freq~lPnries, as shown using left high pass filter 418 and right high pass filter 420, which operate as previously described herein.
The surround sound system 400 also includes a rear speaker 408 which receives the amplified output from amplifier 412. Rear speaker 408 also includes a potentiometer which provides a path to ground for the amplified signal input to rear speaker 408. The potentiometer 409 enables adju~L,ll~llL of the rear speaker acoustic output relative to the output of the other speakers in the system. Rear speaker 408 preferably is adjusted so that the sound pl~S~Ul~ level it produces at the location of the listener is below that produced by the front speaker 415 at that location. This causes the listener to perceive dialog from the front stage in accordance with the prece~i~nre effect of sound reproduction. That is, as between two similar sounds, the human hearing process hlL~ the CA 0221404~ 1997-08-27 W O 97/09851 PCT~US96/14290 2~

direction from which one sound arrives first as the direction from which both sounds are coming.
Because of the psychoacoustic phPn--mPn~ known as time-hltell~iLy trading, higher level sounds are perceived by the listener as arriving earlier. Therefore, by varying the output from rear speaker 408 to a level sufficiently below that of front speaker 406, the sonic image is perceived as being forward, 5 but acoustic energy from rear speaker 408 provides additional acoustic hlrollllalion The hearing process illlclLJl~ this additional hlrolllldlion as ambiance or surround sound. One will also recognize that level adjustment may be accomplished by any of a number of aL,p.~,aclles known to those skilled in the art. In addition, because the clllbodiullcllL~ of Figure 8 utilizes only one channel of ~tnplifi~tion, as cOlll~alcd to two for a stereo configuration, the listener would typically increase the 10 overall system volume to achieve the desired sound plcs~ule level.
As an extension to the fourth embodiment depicted in Figure 8, a similar result can be achieved by applying a monophonic signal to amplifier 212 of Figure 3a, with no input signal being applied to the positive input of amplifler 216. Such an arrangement similarly provides for a ~ul~-~ul1d sound effect based on a monophonic input signal and provides flexibility of a surround 15 sound system configured in Figure 3a for use with both stereo and monophonic signals.
A particularly desirable feature of most surround sound systems is ease of in.ct~ tion and operation to avoid discouraging use by non-terhnir~l COll:iulllcl~. This invention solves most in.ct~ tion difficulties by providing a home theater interconnect module 14 with connPction jacks which confine the system to one and only one possible set of speaker connections for the particular 20 embodiments where the (L-R) difference signals are output to the side speakers. Figure 9 is a wiring diagram showing the hlLeluo~ ection jacks within hll~coll~lect module 14 of Figure 1, and will be described with reference to the components ~liccllcce~l in Figure 1.
IllLelcol~llccL module 14 includes a four tF-tmin~l input jack 30 for receiving the component left and right channel signals input to the hlLelconllecl module 14 from television 12. The 25 left and right channel signals are received via a four conductor wire tf.l.li",.~ g at a four tennin~l connector which mates a~ JlidLcly with four tt-nnin~l input jack 30. The negative inputs for the left and right rh~nnPlc are tied together within hll~ llllect module 14 to provide a common ground signal for each of the input and output c~mnPcti~-n.c. The output to center speaker 20 (of Figure 1) is provided via a three t~rrnin:~l output jack 32 . The three tPrrnin~l c of output jack 32 provide outputs 30 coll~li~hlg the left channel signal, the right channel signal, and a common ground signal. A second three tennin~l sub-woofer output jack 34 provides similar output signals to sub-woofer 18. Sub-woofer output jack 34 similarly provides the left channel signal, the right channel signal, and a common ground signal on the respective t~?tmin~lc.
-CA 022l404~ l997-08-27 A trio of two terrnin~l output jacks 36a, 36b, and 36c provide the left channel signal on one tPnnin~l and the right channel signal on the other termin~l. Each of these jacks interconnect to cables which in turn connect to one of the rear speaker 26, the left satellite speaker 22, and the right satellite speaker 24. The resultant signal provided to those speakers is the left minus right 5 difference signal. The confi~lr~tion of h~ ;v~lect module 14 is thus particularly adapted to the plcrcllcd embodiment shown in Figure 3a where the left satellite speaker 22, right satellite speaker 24, and rear speaker 26 have the dirrclcllce signals as inputs. It will be recognized by one skilled in the art that output jacks 36a, 36b, and 36c are h-le chal1geable because each outputs substantially ~ ntic~l signals.
One of the particularly advantageous features of hlLclcul~lect module 14 is that center speaker output jack 32 and sub-woofer output jack 34 may be i~lrntic~l jacks which output iclentic ~l signals on each terrnin~ Thus, during in~t~ tinn, the olJ~,LdLul may install the system in only one configuration. The vp~ldtor cannot connect the cable connector (not shown) for center speaker 20 or rear speaker 26 to one of output jacks 36a, 36b, or 36c. Similarly, output jacks 36a, 36b, and 36c 15 result in i(1entir~l signals on each terminal. That is, all similarly shaped output (and input) jacks provide (receive) the same signals. Similarly, the u~cldLol cannot connect the cable connector for the satellite or rear speakers to the center speaker output jack 32 or sub-woofer output jack 34. The operator can only connect the cable connector to one of the jacks which outputs the a~Lul~lial~
signal(s) for a particular speaker. In addition, the particular operation of this invention facilitates 20 configuring the h~Lcl'coll--e-;L module 14 to enable ease of in~t~ tinn. Another particularly advantageous feature of the present invention is that the hlLc~;ullllect module 14 is particularly adaptable to standard 2,3, and 4 conductor cables which facilitates low cost m~mlf~rl~lring due to the use of readily available parts.
An enh~nrem~nt to any home theater surround sound system results from reducing 25 the number of components. One approach to component reduction is to consolidate components where possible. For example, lcr~ hlg to Figure 1, interconnect module 14 and sub-woofer 18, may logically be consolidated into a single component. Figure 10 depicts such an alternative configuration for the home theater ~u--uu--d sound speaker system 10 of Figure 1. The home theater surround sound speaker system (surround sound system) 10' of Figure 10 is similarly arranged as in Figure 30 1, and reference numerals in Figure 10 refer to similar components from Figure 1. As can be seen in Figure 10, television 12 outputs an audio signal to integral sub-woofer bass speaker and h~Lc~-;ol~l~ect module 40 (integral bass unit). The integral bass unit 40 performs the combined function of h~Lc~vl~llect module 14 and sub-woofer 18 of Figure 1. IllLcl~;vl~lect module 14 has been incorporated into the sub-woofer bass speaker housing in order to reduce the number of parts and CA 0221404~ 1997-08-27 W O 97/09851 PCT~US96/14290 cabling requirements and to further f~cilit~te in~t~ tion. Integral bass unit 40 in~luclcc an hl~elcollllect portion for di~LlilJulillg the a~ ~liate signals to each of front center speaker 20, left satellite speaker 22, right satellite speaker 24, and rear al~ ce speaker 26. Integral bass unit 40 also inrh~ Ps a sub-woofer directly wired to the hlL~rc~ ect circuitry housed in integral bass unit 40.
5 In this manner, the system requires one less cable (between hllel1omlect module and the sub-woofer bass speaker) and also requires one less individual or stand-alone component (the hlLtlcollllect module).
Figure 11 depicts an exemplary perspective view of integral bass unit 40. Integral bass unit 40 includes an hll~l~;ollllect module 42 having arranged thereon input and output jacks for 0 leCt;iVillg the incoming audio signal and di~ JUlillg the left, right, and difference signals to the pliale speakers. Illlel.;ollllect module 42 includes a four tPrmin~l input jack 44 for receiving via a four conductor wire the left and right channel signals. Interconnect module 42 also includes a three tPrrnin~l center speaker output jack 46 and a trio of two tPrrnin~l output jacks 48a, 48b, and 48c.
IllL~.collllect module 42 is arranged similarly to hllel~:o~ ect module 14 of Fi gure 9 and the principles 15 di~cu~ed with respect to Figure 9 apply equally to Figure 11.
One particular dirrt~ence between hll~l-;ollllect module 42 of Figure 12 and hlLt:icollllect module 14 of Figure 9 is that because hll~l~;onlle~;l module 42 is integrally housed with the sub-woofer bass speaker. illl~l~;ol~llect module 42 does not require a sub-woofer output jack (as does hl~l.;ollllect module 14 of Figure 9). The left channel signal, right channel signal, and common 20 ground signals are fed directly to the cross-over network of integral sub-woofer unit 40.
A particular advantage of a further alternative embodiment of this invention solves the colllllloll problem of many typical consumer viewing rooms not lending themselves to easily cabling the hl~elcol.lle-;L module to the respective satellite and rear alllbiallce speakers. Typically, wiring home theater surround sound systems requires running cable along the walls around the sides 25 and back of the room or drilling down through the floor and pulling cable underneath the viewing room and reentering the viewing room at the respective locations of the speakers.
This invention lends itself particularly to a wireless home theater surround sound speaker c.~ ...lic~tion system 50, as is shown in Figure 13. A television 51 provides the left and right channels of a stereo audio signal to hlL~l.;onllect module 52. Interconnect module 52 distributes 30 the left and right channel signals to the ~ lo~lial~ speakers in order to effect the desired system.
In the embodiment shown in Figure 13, hlL~lcullllect module 52 is wired directly to television 51, front center speaker 54, and sub-woofer 70. In order to Ll~llliL the audio signals to the a~ liate speakers, int~lcom~e~;l module 52 also includes a Lld.~~ el 56 for L~ an audio signal to left satellite speaker 64, right satellite speaker 66, and rear ambiance speaker 68. Each of speakers 64, CA 0221404~ 1997-08-27 66, and 68 inrl~ Pc a receiver 56' to receive the output signal broadcast by L~ rL of hlLel10llllect module 52. Receiver 56' receives the L,,.".~i",i~ l signal and transposes the signal into an audio signal suitable for its les~e~;Live speaker. It will be nn~l~r.ctQod by one skilled in the art that receiver 56' may be configured to output the transposed signal to an amplifier prior to application to the speakers.
Tl~ 56 and lt:cc~ivel 56' pl~r~ldl)ly operate over a single channel. In order to utilize a single channel Ll,."~"il~ ec~iv~, configuration, interconnect module 52 preferably outputs only one audio signal to each speaker. In order to achieve this desirable configuration, the home theater surround sound speaker system 300 of Figure 7 would be the preferable embodiment to implement the wireless ~ullo~ld sound system 50 of Figure 13. In such an embodiment, hlL~:lco~ ect module 52 performs active signal addition and subtraction (as described with respect to Figure 7) to generate the dirrtlcllce and !~u~""~ n signals before ~ cion to the le:j~ecLiv~
speakers. This confi~lration will limit the wireless system to single channel c.J"""".-ic~tion, rather than multiple channel c~"""--l,iC~ m Further, it will be recognized by one skilled in the art that because the left satellite speaker 320, the right satellite speaker 322, and rear speaker 318 are driven by ~"1~ "li~lly i~ nti~l dirÇtile.lce signals, interconnect module 52 can use one Ll~ .llillrl (56, for eY~mple) to Lldn~ a driving audio signal to each of the speakers, thus, resulting in ~ ",I;.,.Ii~l cost savings. It will also be recognized by one skilled in the art that similarly configured receivers and Ll,.n~lllil(~-l.~, could be used to wirelessly connect component speakers which have been described herein as direct wired.
From the r~legohlg it can be seen that this invention solves the several problems found in the prior art and satisfies the several objectives of the invention. This invention thus provides an effective, low-cost, easy to install home theater surround sound system. The front, rear, left, right, and bass speakers provide the desired sound outputs in response to application of the d~l~liate ~""",.~ion and dirrtl~.lce signals resulting form the c(~ ldLion of the left and right 25 channel signals of a stereo signal. The ~,."~,.li~n and difference signal provide the desired dialog and ambiance audio at the d~L~liaL~ speaker.
Although the invention has been described with particular reference to certain preferred embodiments thereof, variations and modifications can be effected within the spirit and scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A speaker system for reproducing a stereophonic audio signal generated by an audio signal source, comprising:
a front speaker for providing an acoustic output in response to a (L + R) input signal, where L is a left channel signal of the stereophonic signal and R is a right channel signal of the stereophonic audio signal;
a rear speaker for providing an acoustic output in response to an input signal varying defined as a difference between the left and right channels;
a left satellite speaker for providing an acoustic output in response to the left input signal;
a right satellite speaker for providing an acoustic output in response to the right input signal; and a bass speaker for providing low frequency acoustic output in response to the (L +
R) input signal;
a means for filtering the input signal to the left satellite speaker to substantially eliminate acoustic frequencies generally less than a predetermined threshold frequency; and a means for filtering the input signal to the right satellite speaker to substantially eliminate acoustic frequencies generally less than a predetermined threshold frequency.

2. The apparatus as defined in claim 1 further comprising an interconnect modulefor receiving the left and right channel signals from the audio signal source and distributing the left and right channel signals to the speakers in a predefined manner.

3. The apparatus as defined in claim 2 wherein the interconnect module further comprises:
an input connector for engaging a corresponding connector of an input cable for providing the stereophonic audio signal from the audio signal source;
a plurality of first output connectors for engaging a corresponding plurality ofconnectors of a plurality output cables for providing an audio signal to each of the bass and center speakers; and a plurality of second output connectors for engaging a corresponding plurality of connectors of a plurality of output cables for providing an audio signal to each of the left, right, and center speakers, the input connector and the first and second output connectors differing to insure proper connection by an operator of the input and output cables to the interconnect module.

4. The apparatus as defined in claim 3 wherein the interconnect module and the bass speaker are integrated to define one component housing both the bass speaker and the interconnect module.

5. The apparatus as defined in claim 4 further comprising an amplifier for receiving and amplifying the left and right channel stereophonic audio signals prior to application to the respective speakers.

6. The apparatus as defined in claim 1 wherein the means for filtering input to the left and light satellite speakers are substantially identical and further comprise first order filters.

7. The apparatus as defined in claim 1 wherein the means for filtering input to the left and right satellite speakers are substantially identical and further comprise second order filters.

8. The apparatus as defined in claim 1 wherein the center speaker further comprises:
a transducer for providing acoustic output from the center speaker, the transducer having first and second voice coils, the first voice coil being responsive to the left channel signal, and the second voice coil responsive to the right channel signal;
wherein the acoustic output of the transducer provides a resultant (L + R) audiosignal.

9. The apparatus as defined in claim 1 wherein the center speaker further comprises:
a first transducer for providing acoustic output from the center speaker, the first transducer having a first voice coil responsive to the left channel signal; and a second transducer for providing acoustic output from the center speaker, the second transducer having a second voice coil responsive to the right channel signal;
wherein the acoustic output of the first and second transducers substantially combined to provide a resultant (L + R) audio signal.

10. The apparatus as defined in claim 1 wherein the rear speaker further comprises:

a transducer for providing acoustic output from the rear speaker, the transducerhaving a voice coil including a first, positive terminal to which is applied the left channel signal and a second, negative terminal to which is applied the right channel signal;
wherein the acoustic output of the transducer provides a resultant (L - R) audiooutput.

11. The apparatus as defined in claim 1 wherein the rear speaker further comprises:
a transducer for providing acoustic output from the rear speaker, the transducerhaving a first voice coil responsive to a first channel signal and a second voice coil responsive to a second channel signal, the second voice coil having the second channel signal applied thereto in a polarity opposite the polarity of the first channel signal applied to the first voice coil;
wherein the transducer provides an acoustical output signal varying in accordance with a difference between the first and second signal.

12. The apparatus as defined in claim 1 wherein the left satellite speaker provides an acoustic output in response to a first difference signal defined in accordance with a difference between the left and right channel signal and the right satellite speaker provides an acoustic output in response to a difference signal defined in accordance with a second difference signal defined in accordance with a difference between the left and right channel signals.

13. The apparatus as defined in claim 12 wherein the first and second differencesignals are substantially identical and the difference signal is defined as one of (L - R) and (R - L) signals.

14. The apparatus as defined in claim 12 wherein one of the difference signals is defined as a (L - R) signal and the other difference signal is defined as a (R - L) signal.

15. The apparatus as defined in claim 12 further comprising:
a left high pass filter for passing to the left satellite speaker audio frequencies of the first difference signal generally greater than a predetermined threshold frequency; and a right high pass filter for passing to the right satellite speaker audio frequencies of the second difference signal generally greater than a predetermined threshold frequency.

16. The apparatus as defined in claim 12 wherein the left and right high pass filters are substantially identical and further comprise a capacitor in series with a positive input terminal of the audio signal applied to the satellite speaker.

17. The apparatus as defined in claim 12 wherein the left and right high pass filters are substantially identical and further comprise:
a capacitor in series with the positive terminal of each satellite speaker; and an inductor in shunt across the positive and negative terminals of each satellite speaker.

18. A speaker system for reproducing a stereophonic audio signal generated by an audio signal source comprising:
a left satellite speaker for providing an acoustic output in response to the left input signal;
a right satellite speaker for providing an acoustic output in response to the right input signal; and a means for filtering the input signal to the left satellite speaker to substantially eliminate acoustic frequencies generally less than a predetermined threshold frequency; and a means for filtering the input signal to the right satellite speaker to substantially eliminate acoustic frequencies generally less than a predetermined threshold frequency.

19. The apparatus as defined in claim 1 further comprising:
a front speaker for providing an acoustic output in response to a (L + R) input signal, where L is a left channel signal of the stereophonic signal and R is a right channel signal of the stereophonic audio signal; and a rear speaker for providing an acoustic output in response to an input signal varying defined as a difference between the left and right channels.

20. The apparatus as defined in claim 18 further comprising an amplifier for receiving and amplifying the left and right channel stereophonic audio signals prior to application to the respective speakers.

21. The apparatus as defined in claim 19 further comprising a bass speaker for providing low frequency acoustic output in response to the (L + R) input signal.

22. The apparatus as defined in claim 18 wherein the means for filtering input to the left and right satellite speakers are substantially identical and further comprise first order filters.

23. The apparatus as defined in claim 18 wherein the means for filtering input to the left and right satellite speakers are substantially identical and further comprise second order filters.

24. The apparatus as defined in claim 18 wherein the center speaker further comprises:
a transducer for providing acoustic output from the center speaker, the transducer having first and second voice coils, the first voice coil being responsive to the left channel signal, and the second voice coil responsive to the right channel signal;
wherein the acoustic output of the transducer provides a resultant (L + R) audiosignal.

25. The apparatus as defined in claim 18 wherein the center speaker further comprises:
a first transducer for providing acoustic output from the center speaker, the first transducer having a first voice coil responsive to the left channel signal; and a second transducer for providing acoustic output from the center speaker, the second transducer having a second voice coil responsive to the right channel signal;
wherein the acoustic output of the first and second transducer substantially combined to provide a resultant (L + R) audio signal.

26. The apparatus as defined in claim 18 wherein the rear speaker further comprises:
a transducer for providing acoustic output from the rear speaker, the transducerhaving a voice coil including a first, positive terminal to which is applied the left channel signal and a second, negative terminal to which is applied the right channel signal;
wherein the acoustic output of the transducer provides a resultant (L - R) audiooutput.

27. The apparatus as defined in claim 18 wherein the rear speaker further comprises:

a transducer for providing acoustic output from the rear speaker, the transducerhaving a first voice coil responsive to a first channel signal and a second voice coil responsive to a second channel signal, the second voice coil having the second channel signal applied thereto in a polarity opposite the polarity of the first channel signal applied to the first voice coil;
wherein the transducer provides an acoustical output signal varying in accordance with a difference between the first and second signal.

28. The apparatus as defined in claim 18 wherein the left satellite speaker provides an acoustic output in response to a first difference signal defined in accordance with a difference between the left and right channel signal and the right satellite speaker provides an acoustic output in response to a difference signal defined in accordance with a second difference signal defined in accordance with a difference between the left and right channel signals.

29. The apparatus as defined in claim 28 wherein the first and second differencesignals are substantially and the difference signal is defined as one of (L - R) and (R - L) signals.

30. The apparatus as defined in claim 28 wherein one of the difference signals is defined as a (L - R) signal and the other difference signal is defined as a (R - L) signal.

31. The apparatus as defined in claim 28 further comprising:
a left high pass filter for passing to the left satellite speaker audio frequencies of the first difference signal generally greater than a predetermined threshold frequency; and a right high pass filter for passing to the right satellite speaker audio frequencies of the second difference signal generally greater than a predetermined threshold frequency.

32. The apparatus as defined in claim 31 wherein the left and right high pass filters are substantially identical and further comprise a capacitor in series with a positive input terminal of the audio signal applied to the satellite speaker.

33. The apparatus as defined in claim 31 wherein the left and right high pass filters are substantially identical and further comprise:
a capacitor in series with the positive terminal of each satellite speaker; and an inductor in shunt across the positive and negative terminals of each satellite speaker.

34. The apparatus as defined in claim 18 further comprising an interconnect module for receiving the left and right channel signals from the audio signal source and distributing the left and right channel signals to the speakers in a predefined manner.

35. The apparatus as defined in claim 18 further comprising:
a front speaker for providing an acoustic output in response to a (L + R) input signal, where L is a left channel signal of the stereophonic signal and R is a right channel signal of the stereophonic audio signal;
a rear speaker for providing an acoustic output in response to an input signal varying defined as a difference between the left and right channels; and a bass speaker for providing low frequency acoustic output in response to the (L +
R) input signal.

36. The apparatus as defined in claim 35 wherein the interconnect module and thebass speaker are integrated to define one component housing both the bass speaker and the interconnect module.

37. The apparatus as defined in claim 35 wherein the interconnect module furthercomprises:
an input connector for engaging a corresponding connector of an input cable for providing the stereophonic audio signal from the audio signal source;
a plurality of first output connectors for engaging a corresponding plurality ofconnectors of a plurality output cables for providing an audio signal to each of the bass and center speakers; and a plurality of second output connectors for engaging a corresponding plurality of connectors of a plurality of output cables for providing an audio signal to each of the left, right, and center speakers, the input connector and the first and second output connectors differing to insure proper connection by an operator of the input and output cables to the interconnect module.

38. A speaker interconnect module for a speaker system which receives a plurality of input signals and distributes to a plurality of speakers output signals formed by various combinations of the input signals, comprising:
an input connector for engaging a corresponding connector of an input cable which provides the input signals to the interconnect module;
at least one first output connector for engaging a corresponding connector of at least one first output cable for providing an audio signal to at least one first speaker; and at least one second output connector for engaging a corresponding connector of at least one second output cable for providing an audio signal to at least one second speaker, the input connector, the first output connector, and the second output connectors each differing to insure proper connection by an operator of the input and output cables to the interconnect module.

39. The apparatus as defined in claim 38 wherein the interconnect module is a separate module from the first and second speaker.

40. The apparatus as defined in claim 38 wherein the interconnect module is integrally housed with one of the first and second speakers to form one component housing both the interconnect module and the one speaker.

41. The apparatus as defined in claim 38 further comprising at least one third output connector for engaging a corresponding connector of at least one third output cable for providing an audio signal to at least one third speaker.

42. The apparatus as defined in claim 38 further comprising at least one fourth output connector for engaging a corresponding connector of at least one fourth output cable for providing an audio signal to at least one fourth speaker.

43. A speaker system for reproducing a stereophonic audio signal generated by an audio signal source and associated with a companion video signal, comprising:a signal preprocessor for generating summation on and difference ((R - L) or (L - R)) output signals based upon a L and R input signal, where L is a left channel signal of the stereophonic signal and R is a right channel signal of the stereophonic audio signal;
a first speaker for providing an acoustic output in response to the summation output signal;

a second speaker for providing an acoustic output in response to the difference output signal;
a third speaker for providing an acoustic output in response to the difference output signal; and a fourth speaker for providing an acoustic output in response to the difference output signal;
a first means for filtering the output signal to the second speaker to substantially eliminate acoustic frequencies generally less than a predetermined threshold frequency; and a second means for filtering the output signal to the third speaker to substantially eliminate acoustic frequencies generally less than a predetermined threshold frequency.

44. The apparatus as defined in claim 43 further comprising a fifth speaker for providing low frequency acoustic output in response to the summation output signal.

45. The apparatus as defined in claim 43 further comprising an amplifier for receiving and amplifying the left and right channel input signals prior to application to the respective speakers.

46. The apparatus as defined in claim 43 wherein the first and second means for filtering are substantially identical and further comprise a first order filter.

47. The apparatus as defined in claim 43 wherein the first and second means for filtering are substantially identical and further comprise a second order filter.

48. The apparatus as defined in claim 43 wherein the preprocessor outputs an (L - R) difference signal input to the second, third, and fourth speakers.

49. The apparatus as defined in claim 43 wherein the preprocessor outputs an (L - R) difference signal input to one of the second and third speakers and to the fourth speaker, and the difference signal is applied to the other of the second and third speakers with a reverse polarity.

50. The apparatus as defined in claim 43 wherein the preprocessor outputs an (R - L) difference signal input to one of the second and third speakers and to the fourth speaker, and the difference signal is applied to the other of the second and third speakers with a reverse polarity.

51. The apparatus as defined in claim 43 wherein the preprocessor outputs an (L
+ R) summation signal input to the first speaker.

52. A speaker system for reproducing a stereophonic audio signal having component left and right channel input signals, comprising:
a front speaker for providing an acoustic output in response to a (L + R) summation signal, where L is a left channel signal of the stereophonic signal and R is a right channel signal of the stereophonic signal;
a pair of side speakers for providing acoustic output in response to the component input signals, where the bandwidth of the component input signals is limited to a frequency above a predetermined threshold frequency; and a rear speaker for providing acoustic output in response to a (L - R) difference signal of the component input signals;
a wireless interconnect module for receiving the left and right channel signals and wirelessly distributing selected combinations of the left and right signals to particular speakers, the wireless interconnect module including at least one transmitter for transmitting a selected combination of the output signals to the respective speakers; and a receiver associated with a particular speaker for receiving the transmitted signal from the at least one transmitter, the receiver receiving the transmitted signal and outputting an electronic signal input to the speaker.

53. The apparatus as defined in claim 52 further comprising a fifth speaker for providing low frequency acoustic output in response to a summation signal of the component input signals.

54. The apparatus as defined in claim 53 wherein the fifth speaker is responsive to a summation (L + R) input signal, where L is a left channel signal of the stereophonic signal and R is a right channel signal of the stereophonic audio signal.

55. The apparatus as defined in claim 52 wherein the pair of side speakers is responsive to a (L - R) difference signal ((R - L) or (L - R)), where L is a left channel signal of the stereophonic signal and R is a right channel signal of the stereophonic audio signal.

56. The apparatus as defined in claim 55 wherein the rear speaker is responsive to the difference signal.

57. The apparatus as defined in claim 52 wherein the front speaker is responsiveto a summation (L + R) input signal, where L is a left channel signal of the stereophonic signal and R is a right channel signal of the stereophonic audio signal.

58. A speaker system for reproducing a monophonic audio signal generated by an audio signal source, comprising:
a front speaker for providing an acoustic output in response to the monophonic audio signal;
a rear speaker for providing an acoustic output in response to the monophonic audio signal;
a left satellite speaker for providing an acoustic output in response to the monophonic audio signal;
a right satellite speaker for providing an acoustic output in response to the monophonic audio signal; and a bass speaker for providing low frequency acoustic output in response to the monophonic audio signal;
a means for filtering the monophonic audio signal input to the left satellite speaker to substantially eliminate acoustic frequencies generally less than a predetermined threshold frequency;
and a means for filtering the monophonic audio input to the right satellite speaker to substantially eliminate acoustic frequencies generally less than a predetermined threshold frequency.

59. The apparatus as defined in claim 58 further comprising an amplifier for receiving and amplifying the monophonic audio signals prior to application to the respective speakers.

60. The apparatus as defined in claim 58 wherein the means for filtering input to the left and right satellite speakers are substantially identical and further comprise first order filters.

61. The apparatus as defined in claim 58 wherein the means for filtering input to the left and right satellite speakers are substantially identical and further comprise second order filters.

62. The apparatus as defined in claim 58 further comprising:
a left high pass filter for passing to the left satellite speaker audio frequencies of the monophonic audio signal generally greater than a predetermined threshold frequency; and a right high pass filter for passing to the right satellite speaker audio frequencies of the monophonic audio signal generally greater than a predetermined threshold frequency.

63. The apparatus as defined in claim 62 wherein the left and right high pass filters are substantially identical and further comprise a capacitor in series with a positive input terminal of the audio signal applied to the satellite speaker.

64. The apparatus as defined in claim 62 wherein the left and right high pass filters are substantially identical and further comprise:
a capacitor in series with the positive terminal of each satellite speaker; and an inductor in shunt across the positive and negative terminals of each satellite speaker.

65. A speaker system for reproducing a stereophonic audio signal generated by an audio signal source, comprising:
a front speaker for providing an acoustic output in response to a (L + R) input signal, where L is a left channel signal of the stereophonic signal and R is a right channel signal of the stereophonic audio signal;
a rear speaker for providing an acoustic output in response to an input signal varying defined as a difference between the left and right channels:
a left satellite speaker for providing an acoustic output in response to a difference signal defined as the difference between the left and right signal ((L-,.beta.R) or (R-.beta.L)), where .beta. is defined as a gain factor for the subtracted signal;
a right satellite speaker for providing an acoustic output in response to the difference signal;
a bass speaker for providing low frequency acoustic output in response to the (L +
R) input signal;
a means for filtering the difference signal input to the left satellite speaker to substantially eliminate acoustic frequencies generally less than a predetermined threshold frequency;
and a means for filtering the difference signal input to the right satellite speaker to substantially eliminate acoustic frequencies generally less than a predetermined threshold frequency.

66. The apparatus as defined in claim 65 further comprising at least one amplifier for receiving and attenuating the subtracted left and right channel stereophonic audio signals of the difference signal, the amplifier gain .beta. having one of a value varying from zero to unity and a continuously variable value between zero and unity.

67. The apparatus as defined in claim 65 wherein the left satellite speaker receives a first difference signal defined as one of (L-.beta.R) or (R-.beta.L) and the right satellite speaker receives the other difference signal of (L-.beta.R) or (R-.beta.L).

68. The apparatus as defined in claim 65 wherein the means for filtering input to the left and right satellite speakers are substantially identical and further comprise first order filters.

69. The apparatus as defined in claim 65 wherein the means for filtering input to the left and right satellite speakers are substantially identical and further comprise second order filters.

70. The apparatus as defined in claim 65 further comprising:
a left high pass filter for passing to the left satellite speaker audio frequencies of the first difference signal generally greater than a predetermined threshold frequency; and a right high pass filter for passing to the right satellite speaker audio frequencies of the second difference signal generally greater than a predetermined threshold frequency.

71. A speaker system for reproducing a stereophonic audio signal generated by an audio signal source and associated with a companion video signal, comprising:a signal preprocessor for generating summation and difference ((R -.beta.1L) or (L -.beta.2R)) output signals based upon a L and R input signal, where L is a left channel signal of the stereophonic signal and R is a right channel signal of the stereophonic audio signal and .beta.1 and .beta.2 are defined as gains for the respective subtracted signals;
a first speaker for providing an acoustic output in response to the summation output signal;
a second speaker for providing an acoustic output in response to the difference output signal;

a third speaker for providing an acoustic output in response to the difference output signal; and a fourth speaker for providing an acoustic output in response to the difference output signal;
a first means for filtering the output signal to the second speaker to substantially eliminate acoustic frequencies generally less than a predetermined threshold frequency; and a second means for filtering the output signal to the third speaker to substantially eliminate acoustic frequencies generally less than a predetermined threshold frequency.

72. The apparatus as defined in claim 71 further comprising a fifth speaker for providing low frequency acoustic output in response to the summation output signal.

73. The apparatus as defined in claim 71 further comprising a pair of amplifiershaving gains .beta.1, and .beta.2, respectively, for receiving and amplifying the left and right channel input signals, respectively, to produce .beta.1L and .beta.2R signals prior to subtraction to form the difference signals.

74. The apparatus as defined in claim 71 wherein .beta.1, and .beta.2 are equal.

75. The apparatus as defined in claim 74 wherein .beta.1, and .beta.2 may be varied between zero and unity.

76. The apparatus as defined in claim 71 wherein .beta.1 and .beta.2 each may be varied independently.

77. The apparatus as defined in claim 71 wherein the first and second means for filtering are substantially identical and further comprise a first order filter.

78. The apparatus as defined in claim 71 wherein the first and second means for filtering are substantially identical and further comprise a second order filter.