Patent ID: 6760447
Filing Date: 2004-07-06
Classification: H04R,H04S

Abstract:
A sound reproduction system comprising loudspeaker means, and loudspeaker drive means for driving the loudspeaker means in response to signals from at least one sound channel, the loudspeaker means comprising a closely-spaced pair of loudspeakers, the loudspeaker drive means comprising filter means, the filter means comprising at least one pair of filters, an output of one filter of the pair of filters being applied to one loudspeaker of said pair of loudspeakers, an output of the other filter of the pair of filters being applied to the other loudspeaker of said pair of loudspeakers, the filter means having characteristics which are so chosen as to produce virtual images of sources of sound associated with the at least one sound channel at virtual source positions which subtend an angle at a predetermined listener position that is substantially greater than an angle subtended by the loudspeakers, characterised in that the loudspeakers define with the listener position an included angle of between 6Â° and 20Â° inclusive, and that the outputs of the pair of filters result in a phase difference between vibrations of the two loudspeakers where the phase difference varies with frequency from low frequencies where the vibrations are substantially out of phase to high frequencies where the vibrations are in phase, the lowest frequency at which the vibrations are in phase being determined approximately by a ringing frequency, f0 defined byf0=1/2 &tgr;where Ï„=Ï„=r2-r1co,andwhere r2 and r1 are the path lengths from one loudspeaker centre to the respective ear positions of a listener at the listener position, and c0 is the speed of sound, said ringing frequency f0 being at least 5.4 kHz.