Sound system and method of sound reproduction

A system for adaptive sound reproduction in a manner so as to enlarge the perceived area and stability of a stereo sound image, comprising:

• a left speaker and a right speaker located in close proximity;
• a left channel audio signal;
• a right channel audio signal;
• a subtractor receiving as inputs said left channel audio signal and right channel audio signal, and outputting a difference signal representing a difference between said left channel audio signal and said right channel audio signal;
• a spectral weighting filter receiving said difference signal as an input and outputting a spectrally weighted signal;
• a cross-cancellation circuit for mixing said spectrally weighted signal with said left channel audio signal and said right channel audio signal, thereby generating a first speaker signal for said left speaker and a second speaker signal for said right speaker;
• a phase equalizer interposed between said spectral weighting filter and said cross-cancellation circuit;
• a first phase compensator interposed between said left channel audio signal and said cross-cancellation circuit, said first phase compensator having a phase characteristic complementary to a combined phase characteristic of said phase equalizer and said spectral weighting filter;
• and
• a second phase compensator interposed between said right channel audio signal and said cross-cancellation circuit, said second phase compensator having a phase characteristic complementary to said combined phase characteristic.

A method of sound reproduction, comprising the steps of:

• placing a left speaker and a right speaker in close proximity;
• receiving a left channel audio signal;
• receiving a right channel audio signal;
• generating a difference signal representing a difference between said left channel audio signal and said right channel audio signal;
• applying a spectral weighting to said difference signal thereby generating a spectrally weighted signal;
• cross-canceling said spectrally weighted signal with said left channel audio signal and said right channel audio signal, thereby generating a first speaker signal for said left speaker and a second speaker signal for said right speaker;
• performing phase equalizatlon on said difference signal prior to said step of cross-canceling said spectrally weighted signal with said left channel audio signal and said right channel audio signal;
• and
• performing phase compensation on each of said left channel audio signal and right channel audio signal to compensate for the spectral weighting and phase equalization performed on said difference signal;
• wherein said step of performing phase equalization on said difference signal is carried out using a first plurality of all pass filters collectively having a first phase transfer function, and wherein said step of performing phase compensation on each of said left channel audio signal and right channel audio signal is carried out using a second and third plurality of all pass filters, said second plurality of all pass filters and said third plurality of all pass filters each having a collective phase transfer function complementary to a combined phase transfer function of said first phase transfer function and a spectral weighting phase transfer function associated with the step of applying spectral weighting to said difference signal.

A method for adaptively reproducing sound in a manner so as to enlarge the perceived area end stability of a stereo sound image, the method comprising the steps of:

• placing a left speaker and a right speaker in close proximity;
• receiving a left channel audio signal;
• receiving a right channel audio signal;
• generating a spectrally weighted difference signal by obtaining a difference signal representing a difference between said left channel audio signal and said right channel audio signal, and applying said difference signal to a spectral weighting filter;
• and
• cross-canceling said spectrally weighted stereo difference signal with said left channel audio signal and said right channel audio signal prior to applying said left channel audio signal and said right channel audio signal to said left speaker and said right speaker, respectively, said spectrally weighted difference signal derived from said left channel audio signal and said right channel audio signal;
• and
• performing phase equalization on an output of said spectral weighting filter prior to said step of cross-canceling said spectrally weighted stereo difference signal with said left channel audio signal and said right channel audio signal;
• wherein said step of performing phase equalization on said output of said spectral weighting filter is carried out using a first plurality of all pass filter, and wherein said step of performing phase compensation on each of said left channel audio signal and right channel audio signal is carried out using a second and third plurality of all pass filters.

A sound reproduction system for a surround sound stereophonic system, comprising:

• a surround left speaker;
• a surround right speaker;
• a pair of surround back speakers located in close proximity;
• a surround left channel audio signal electrically connected to said surround left speaker;
• a surround right channel audio signal electrically connected to said surround right speaker;
• and
• a sound processor receiving as inputs said left channel audio signal and said right channel audio signal, said sound processor configured to generate a difference signal representing a difference between said surround left channel audio signal and said surround right channel audio signal, apply a spectral weighting to said difference signal thereby generating a spectrally weighted signal, and cross-cancel said spectrally weighted signal with said surround left channel audio signal and said surround right channel audio signal, thereby generating a first speaker signal and a second speaker signal for said pair of surround back speakers;
• wherein said sound processor further comprises a phase equalizer for equalizing the phase of said difference signal prior to cross-cancellation, and a plurality of phase compensators complementary in phase characteristics to a combined phase characteristic of said phase equalizer and said spectral weighting filter, said phase compensators placed in series along each of said surround left channel audio signal and surround right channel audio signal, respectively, prior to cross-cancellation.