Harman Motive Inc.

Other

Harman International Industries, Inc.

Sound Advance Systems, Inc.

Michael L Petroff

A digital signal processing technique is provided for symmetrical stereophonic image enhancement in an automotive listening environment. The process introduces a rapid rate-of-change of phase shift between the channels, to a maximum of substantially 180 degrees, at substantially 200 Hertz. As an additional feature, spatial enhancement of the reproduced sound may be provided through the application of modified stereo difference signals prior to the image enhancement process.

Digital signal processing for symmetrical stereophonic imaging in automobiles

A frequency response compensation system for use with a planar diaphragm speaker mounted in an architectural wall, ceiling or sealed enclosure having a depth dimension limited by the interior depth of the ceiling, wall or enclosure. The compensation system combines signals derived from a modified high-pass filter stage, an unmodified signal path, and a gyrator stage so as to phase-interact with one another and provide a complex transfer function. An underdamped high-pass filter stage further enhances low bass performance. The frequency compensation system includes a main circuit board and a series of daughter boards that are adapted to be releasably connected to the main board. Each of the daughter boards contains a set of passive components having different component values that determine the specific response parameters of the various stages and circuits of the compensation system and is optimized for a specific planar speaker and enclosure combination. A multi-section switch for selecting between different sets of component values may be substituted for the daughter boards.

Compensation system for planar loudspeakers

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.

Stereophonic image enhancement system for use in automobiles

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. The left and right stereo signals are filtered according to a transfer function having low-bass cutoff frequency selected to minimize reproduction distortion by minimizing low frequency signal components below an effective frequency range of the loudspeakers. The filtered stereo signals are separately mixed in optimal proportion with the equalized and filtered difference signals, thereby providing optimal spatial enhancement for small and closely-spaced stereo loudspeakers.

Stereo spatial enhancement system

A stereophonic signal processing system for enhancing the perception of sonic dimension and imaging in a sound reproduction system having at least two stereo speakers. The system provides a detector for detecting the continually changing value of amplitude ratio of a derived stereo difference signal relative to a derived stereo sum signal and dynamically expands, in real-time, changes in such ratio-value in the left-front and right-front output signals; an element for utilizing the ratio-value to control a decrease in the amplitudes of the front-left and front-right output signals; an element for utilizing the ratio-value to control a boost in the relative amplitude of bass frequencies in the left-front and right-front output signals and a boost in the amplitude of a subwoofer output signal; an element for utilizing the ratio-value to control a boost in amplitude of derived stereo difference signals that provide left-rear and right-rear output signals; and an element for utilizing the derived stereo sum signal to provide a center-front output signal.

Dynamic stereophonic enchancement signal processing system

The present invention is an improved two-channel, four loudspeaker-component enhanced stereophonic system which includes a pair of front loudspeaker systems, a pair of rear loudspeaker systems and a pair of speaker enclosures into each of which one of the front loudspeaker systems and one of the rear loudspeaker systems are placed. The enhanced stereophonic system also includes two electronic matrix networks which interconnect the input terminals of each front loudspeaker system to the left and right channel amplifier output terminals, respectively, and which also interconnect the positive input terminal of each rear loudspeaker system to the left and right channel positive amplifier output terminals, respectively. The electronic matrix networks include a first high-pass filter and a second high-pass filter each of which has an input terminal and an output terminal. The input terminal of the first high-pass filter is interconnected to the left channel positive amplifier output terminal. The output terminal of the first high-pass filter is interconnected to the negative input terminal of the second rear loudspeaker system. The input terminal of the second high-pass filter is interconnected to the right channel positive amplifier output terminal. The output terminal of the second high-pass filter is interconnected to the negative input terminal of the first rear loudspeaker system. Each electronic matrix network also includes a resistive attenuation circuit whereby the output levels of the rear loudspeaker systems may be adjusted.

Growing community of inventors

West Hills, CA, United States of America

Michael L Petroff