In the early days of Compact Disc, a number of discs were mastered using an existing quadraphonic mix. Where a matrixed quadraphonic mix was used to master the Compact Disc, this inadvertently resulted in a Compact Disc that can be played back through a suitable decoder to reproduce quadraphonic sound.
Quadraphonic releases were more common in the 1970s, but quadraphonic wasn’t a commercial success, partly due to the number of competing standards and also because to listen to quadraphonic sound required a suitable decoder as well as additional speakers. Despite this, some music was only ever mixed for quadraphonic sound, and so was the only mix available when it came to first releasing an album on Compact Disc.
Matrixed quadraphonic formats that were used for LP records, such as QS, SQ and EV Stereo-4, can be successfully decoded from Compact Disc since matrixed recordings encode and decode 4-channels of audio information in a 2-channel medium. Because of this, a number of early Compact Disc releases contain quadraphonic sound, though this is only occasionally mentioned on the disc or the cover.
Four-channel Compact Disc recordings were contemplated, and this is briefly mentioned in the Red Book specification of 1980 as well as later editions, but was not fully specified. No mass-market Compact Discs have used more than two-channels.
More recently, surround sound has been available through formats such as Super Audio CD (SACD), DVD-Audio and High Fidelity Pure Audio (Blu-ray).
Figures
Dimensions: 120 mm × 1.2 mm