Quadraphonic Sound (QS) was developed at Sansui and introduced in 1972. It is a matrix format for quadraphonic sounds from the 12-inch LP vinyl record. It was also referred to as Regular Matrix (RM).
The format was freely licensed to record companies, and was used by a number of them. It offered excellent diagonal separation and was compatible with stereo systems.
Some systems were compatible with both QS and SQ formats, and QS was compatible with the original EV format, and can synthesise quadraphonic sound from standard stereo records.
The tracks on the QS vinyl LP are the same width as standard stereo tracks, so playing time is the same as conventional 12-inch LPs.
The last adverts for QS systems appeared in 1978.