Method and apparatus for spatially enhancing stereo and monophonic signals

A system for enhancing a stereo image comprising first and second signals, said system comprising:

• first and second input terminals for receiving said first and second signals, respectively;
• first and second output terminals for providing first and second enhanced signals, respectively;
• a first op-amp having first and second input terminals and an output terminal, said first input terminal of said first op-amp coupled to said first input terminal of said system, said output terminal of said first op-amp coupled to said first output terminal of said system, said second input terminal of said first op-amp being coupled to said second input terminal of said system via a resistive element;
• a feedback network coupled between said output and second input terminals of said first op-amp;
• and
• a second op-amp having first and second input terminals and an output terminal, said first input terminal of said second op-amp coupled to said first and second input terminals of said system, said second input terminal of said second op-amp coupled to said first output terminal of said system, said output terminal of said second op-amp coupled to said second output terminal of said system.

A method for spatially enhancing an input signal which may be either a monophonic signal or a stereophonic signal, said method comprising the steps of:

• receiving first and second input channels indicative of said input signal;
• summing said first and second channels to produce a sum signal;
• phase-shifting said sum signal using an all-pass filter to produce an enhanced sum signal;
• combining said enhanced sum signal with said first input channel to produce an intermediate signal;
• filtering said intermediate signal using a low-pass filter to produce a first output channel;
• and
• combining said first and second input channels and said first output channel to produce a second output channel,
• wherein said first and second output channels are indicative of a spatially enhanced signal.

A system for spatially enhancing an acoustic image comprising first and second input signals to produce an enhanced acoustic image comprising first and second output signals, said system comprising:

• means for summing said first and second input signals to produce a sum signal;
• means for enhancing said sum signal to produce an enhanced sum signal;
• means for combining said enhanced sum signal and said first and second input signals to produce said first output signal;
• and
• means for summing said first output signal and said first and second input signals to produce said second output signal.

A system for spatially enhancing an input signal comprising first and second input channels which may be indicative of either a monophonic image or a stereophonic image, said system comprising:

• means for receiving first and second input channels indicative of said input signal;
• means for summing said first and second channels to produce a sum signal;
• means for phase-shifting said sum signal using an all-pass filter to produce an enhanced sum signal;
• means for combining said enhanced sum signal with said first input channel to produce an intermediate signal;
• means for filtering said intermediate signal using a low-pass filter to produce a first output channel;
• and
• means for combining said first and second input channels and said first output channel to produce a second output channel, wherein said first and second output channels are indicative of a spatially enhanced signal.

A system for spatially enhancing an input signal comprising first and second input channels indicative of an input acoustic image to produce first and second output channels indicative of a spatially enhanced acoustic image, said system comprising:

• a first op-amp having non-inverting and inverting terminals each coupled to receive said first and second input channels, said first op-amp providing a first enhanced sum signal at an output terminal thereof;
• a second op-amp having non-inverting and inverting terminals coupled to said output terminal of said first op-amp, said second op-amp providing a second enhanced sum signal at an output terminal thereof;
• a third op-amp having a non-inverting terminal coupled to receive said first input channel and said second enhanced sum signal and having an inverting terminal coupled to receive said second input channel, said third op-amp providing said first output channel at an output terminal thereof;
• and
• a fourth op-amp having a non-inverting terminal coupled to receive said first and second input channels and having an inverting terminal coupled to receive said first output channel, said fourth op-amp providing said second output channel at an output terminal thereof.