QS Regular Matrix

File:QS Regular Matrix logo.png

QS Regular Matrix logo

Quadraphonic Sound (originally called Quadphonic Synthesizer, and later referred to as RM or Regular Matrix) was a matrix 4-channel quadraphonic sound system based on the same principles as laid down by Peter Scheiber, but developed by engineer Ryosuke Ito of Sansui in the early 1970s.

It was adopted by ABC, Advent, Bluesway, Candide, Command, Decca, Impulse, Longines, MCA, Pye, Turnabout and Vox record companies. It was freely licensed to record companies.

The concept of Regular Matrix was often used a synonym to QS, but was actually a standard set by the Japanese governing body, which also embraced the QM and QX matrix systems.

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. The QS record track is as small as a conventional stereo track, so the maximum playing time is the same as conventional stereo records.

History

As early as 1969 engineer Peter Scheiber developed a matrix system very similar to QS. He also was instrumental in many improvements to SQ (see above) quality, in collaboration with Martin Willcocks and Jim Fosgate.

In the early 1970 Sansui introduce the Four Channel Synthesizer Decoder QS-1 and the QSE-1 Encoder based on the QS system in Japan and debuted export to the United States in march 1971. The channel separation was only 3 dB, but because of the human way of hearing it sounded relatively good.

In 1973 Sansui introduced the QS Vario Matrix decoder with 20 dB separation in all directions. (The Vario Matrix decoder could also play SQ records on Phase Matrix mode with 6 dB separation. Later Sansui used front-rear logic on the SQ mode.) Two outboard decoders, the QSD-1 and QSD-2, as well as the QRX series of larger receiver-amplifiers, incorporated this matrix and up-conversion. Sansui's QS decoders also had good stereo-to-quad capabilities, wrapping the L-R panorama to LB-LF-RF-RB in a horseshoe topology. (The Vario Matrix decoder could synthesize four channel sound with high separation - at least 12 dB.)

The system was often called RM (Regular Matrix) when used on amplifiers or receivers by other trademarks than Sansui. Many Japanese trademarks like Pioneer or Kenwood had matrix decoders with two modes: - SQ and RM. JVC had two modes on their matrix decoder called Matrix 1 and Matrix 2. That decoder could play both SQ and QS records, but it was a simplified decoder. QS records could also be played on Marantz Vari-Matrix system. (European trademarks like Philips or Bang & Olofsen had only decoders for SQ or both SQ and CD-4 - but not QS.) QS records could give some quadraphonic effect, although far from accurate, when played on an SQ decoder.

The QS matrix system was employed to create the five-channel Quintaphonic Sound system used for première engagements of the 1975 film Tommy. The left and right 35 mm magnetic soundtracks were QS-encoded to create four channels around the cinema audience, while the centre mag track was assigned to the speaker behind the screen. The mag FX track was unused. This channel layout came close (5.0) to the now common 5.1 surround sound layout.

Usage

QS Encoding Matrix	Left Front	Right Front	Left Back	Right Back
Left Total	0.92	0.38	j0.92	j0.38
Right Total	0.38	0.92	-j0.38	-j0.92

j = + 90° phase-shift

When played on a conventional two channel stereo equipment, the front channels are narrower than ordinary two channels because of the low separation. But the rear channels are heard from points outside the ordinary stereo spectrum. So the QS record gives a totally broader stereo picture than conventional two channel stereo. The point behind the listener is out of phase when played in two channel stereo and extinct in one channel mono listening. In mono the volumes of left and right points behind the listener is reduced with only 3 dB (in SQ 6 dB). (Source: Kjell Stensson: 4-kanalstekniken ännu i startgroparna, in Stereo Hi Fi Handboken 74, Svenska HiFi Institutet 1973, page 30).

Quintaphonic Sound

A five-channel system based on QS, named Quintaphonic Sound, was used for the 1975 film Tommy.

The left and right 35mm magnetic soundtracks were QS encoded to create four channels around the cinema audience, while the center magnetic track was assigned to the speaker behind the screen. This channel layout (5.0) was a precursor to the current 5.1 surround sound arrangement.

Hardware

The QSD-1 Quadphonic Synthesizer (a rack-mount module) was introduced in 1971, soon followed by the smaller, boxy QSD-2.

Bibliography

• R. Ito and S. Takahashi, Characteristics of the Sansui QS Vario-Matrix (presented at the Audio Engineering Society 43rd Convention, Los Angeles, September 1972) read on-line
• R. Ito, “Proposed universal encoding standard for compatible four-channel matrixing,” JAES April 1972. (First presented at the 41st A.E.S Convention, 7th October 1971). Also reprinted in “Quadraphony” Anthology, AES 1975 pp. 125-131.
• Sansui QS Tech Manual (QSD-1) read on-line

References

There is now an Australian Company Involve Audio That Makes a QS decoder The Same spec,s as the QSD1 a 3 band decoder Surround Master