A system for tensioning a membrane within a frame for a loudspeaker or a microphone is characterized by a frame containing an opening, a membrane connected to an exterior surface of the frame and spanning the frame opening, and a tensioning device connected with the frame for deflecting a portion of...http://www.google.co.uk/patents/US6728389?utm_source=gb-gplus-sharePatent US6728389 - Membrane support system
