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Quadraphonic sound uses four channels in which speakers are positioned at all four corners of the listening
space, reproducing signals that are independent of each other.
History
Quadraphonic sound was one of the earliest consumer offerings in multichannel audio, introduced to the American market in the early 1970s. Quad was not one format but a myriad of different and largely incompatible formats on different
media: quadraphonic could be obtained from vinyl records,
eight tracks, and reel-to-reel. Further complicating
quadraphonic was the fact that some systems were discrete, while others were
matrix.
Formats
CD-4
Compatible Discrete 4 or Quadradisc was introduced in 1971 as a discrete quadraphonic system created by
JVC (as a subsidiary of RCA). This format was less
popular than others because of incompatibility, poor longevity, and strict setup requirements. The quadraphonic music was encoded
with sum and difference signals on the standard stereo grooves of vinyl. To play back the record, a special cartridge and stylus
was required, in addition to a CD-4 demodulator and the usual quadraphonic receiver. This system produced additional wear and
tear, so JVC introduced "super vinyl", a very durable type of record.
Quad-8
Quadraphonic 8-Track was a discrete system introduced by RCA in late 1970. The format was almost identical in
appearance to stereo 8-tracks except for a small notch in the upper left corner of the cartridge. This signaled a quadraphonic
8-track player to combine the odd tracks as audio channels for Program 1 and the even tracks as channels for Program
2. The format was completely incompatible with stereo or mono players, but quadraphonic players would play stereo 8-tracks.
Some stereo 8-track players touted simulated quadraphonic sound (through upmixing stereo 8-tracks) but were not
quadraphonic 8-track players. The last release in the quadraphonic 8-track format was in 1978.
SQ
Surround Quadraphonic was a matrix quadraphonic system for vinyl. It was introduced by CBS in 1972. The system is based on the work of Peter Scheiber, who created the basic mathematical formulas used to
matrix four channels into two in 1970. (Some sources state that "SQ" is an acronym for "Stereo Quadraphonic." This makes sense
since without a quad decoder SQ encoded records play as a normal stereo record and CBS stated their desire to maintain excellent
compatibility of their SQ encoded records with standard stereo systems.)
QS
Reel to reel
External links
http://www.geocities.com/quadaudio/ A great site for learning about quadraphonics.
Given a coveted "Right On" award by the Surround Sound Society
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