In the concert hall the listener experiences direct sound from the stage providing directional information, and reflected sound from all directions providing hall ambience information, or depth. Conventional quadrasonic systems can provide ambience signals, mainly from the read speakers, while the front speakers deliver direct sound. Previous studies have shown that three channels are required for the optimum stereo reproduction of a distributed source, that the listener's ability to perceive the direction of sources from the rear is reduced, and that the hall ambience signal provides little directional information. In the light of these considerations, a new configuration for the four available channels is proposed, three front channels and one rear. Comparison tests between the proposed "3 + 1" system and standard quadrasonic show marked listener preference for the new configuration, based largely on the ease and stability of sound source location. The loss of stereo information from the rear was judged insignificant.
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