QS Regular Matrix

Quadraphonic Sound (originally called Quadphonic Synthesizer, and later incorrectly referred to as RM or Regular Matrix) was a phase amplitude matrix 4-channel quadraphonic sound system for phonograph records. The system was based on technology created by Peter Scheiber, but further developed by engineer Ryosuke Ito^[1][2] of Sansui in the early 1970s.

The technology was freely licensed and was adopted by many record labels including ABC, Advent, BluesWay, Candide, Command, Decca, Impulse, Longines, MCA, Passport, Pye, Turnabout and Vox. More than 600 LP record titles using this technology were released on vinyl during the 1970s.^[3][4][5]

RM (Regular Matrix) was often used a synonym for the 'Sansui QS', 'Toshiba QM' and 'Nippon Columbia QX' matrix systems that were previously launched before the advent of the RM specification in 1973. Although none of the three previous matrices were compatible with the new RM specification, and with Toshiba and Nippon Columbia withdrawing their 'further RM incompatible' matrix systems from the market, Sansui's QS system was unofficially labelled by some record labels as RM, until the situation was clarified to those responsible for the mislabeling.^{[6][7][8][9][10][11]}

The QS matrix has been found to offer the advantages of excellent diagonal separation and stereo compatibility, and although the adjacent speaker separation is only 3 dB, this symmetrical distribution produces more stable quadraphonic images than some other matrix systems. The QS record track width is as narrow as a conventional stereo track, so the maximum playing time is the same as conventional stereo records.