Patent ID: 8488415

Claim:
An electro-dynamic acoustic transducer system comprising: a rigid enclosure having an open end; a pressure compensated chamber extending into the rigid enclosure from the open end; a vibratile piston located in the open end of the rigid enclosure to have an axis of oscillation perpendicular to the plane of the open end; the vibratile piston being located in the open end to close the pressure compensated chamber; the vibratile piston having an anterior major surface exposed from the open end; a magnet assembly attached to the vibratile piston; a stator coil positioned with respect the rigid enclosure to interact with the magnet structure upon application of an electrical signal to the stator coilfor generating forces to move the vibratile piston; the pressure compensated chamber being responsive to changes in ambient pressure by changes in volume for balancing its internal pressure with ambient pressure; the pressure compensated chamber providing a tuned backchamber for the vibratile piston; and a valve allowing adjustment of the internal pressure of the pressure compensated chamber to determine the volume of the pressure compensated chamber at known ambient pressures.