Abstract: A stereophonic image enhancement signal processing system for vehicular sound systems provides a symmetrical improvement in imaging for listeners located at the left and right regions of a vehicle passenger compartment The stereo signals are processed in a manner to provide a rapid rate-of-change of phase equal to at least 90 degrees per octave approaching a maximum of 180 degrees between the stereo channels at approximately 300 Hz. A further enhancement of the reproduced sound stage is provided through the application of equalized stereo difference signals prior to, and in combination with, the above described phase shift process. An optional center channel signal, summed from stereo source signals, may be provided for driving a central speaker.

Abstract: A stereophonic signal processing system provides optimal spatial enhancement in a compact stereo sound system having limited physical separation between two relatively small stereo loudspeakers with accordingly limited low-frequency output capability. A difference signal is derived from the left and right stereo signals by subtraction in a a differential amplifier circuit, which may be made frequency-dependent so that the rejection of correlated information decreases with increasing frequency. The difference signal is processed through a frequency equalizer circuit, and an inverted version is derived via an inverter; the non-inverted and inverted difference signals are filtered according to a high-pass filter function having an upper-bass cutoff frequency selected to avoid excessive spatialization at low frequencies.

Abstract: A bimorph bender acoustical transducer driver or motor element in which no center vane is necessary. Elimination of the vane reduces the dynamic mass of the driver so that a thicker, more rugged piezoelectric wafer can be used to achieve the same acoustical response characteristics as were possible with prior art drivers having vanes and thinner piezoelectric wafers subject to damage.