Audio stereo processing method, device and system

Device for processing an input audio stereo signal comprising two input signals, for reproduction of a processed stereo signal in an audio stereo reproduction system comprising at least one pair of loudspeaker elements, the device comprising:

• a) means for producing a left output signal for transmission to a left loudspeaker in said pair, which is, or is equivalent to, the sum of the mid input signal (M) and the side input signal (S),
• b) means for producing a right output signal for transmission to a right loudspeaker in said pair, which is, or is equivalent to, the sum of the mid input signal (M) and the side signal (S) phase shifted 180°,
• the device further being characterised in that it comprises:
• c) means for phase shifting at least a part of the side input signal (S) or the mid input signal (M) in the frequency range 4 kHz-9 kHz at least 45° but no more than 135° relative to the other signal prior to or at the production of the left and right output signals in steps a) and b).

System, for reproduction of an input audio stereo signal comprising two input signals consisting of a mid input signal (M) and a side input signal (S), or of a kind from which a mid input signal (M) and a side input signal (S) are derivable, such as a left input signal (L) and a right input signal (R), comprising a pair of loudspeaker elements, the system further comprising:

• a) means for producing a left output signal for transmission to a left loudspeaker in said pair, which is, or is equivalent to, the sum of the mid input signal (M) and the side input signal (S),
• b) means for producing a right output signal for transmission to a right loudspeaker in said pair, which is, or is equivalent to, the sum of the mid input signal (M) and the side signal (S) phase shifted 180°,
• the system further being characterised in that it comprises:
• c) means for phase shifting at least a part of the side input signal (S) or the mid input signal (M) in the frequency range 4 kHz-9 kHz at least 45° but no more than 135° relative to the other signal prior to or at the production of the left and right output signals in steps a) and b).