Quadraphonic
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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.
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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 myriad 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. There were even some experiments with radio broadcasts, although they were short lived.
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 not entirely compatible with stereo or mono players - although quadraphonic players would play stereo 8-tracks, playing quadraphonic tapes on stereo players results in hearing only one-half the channels at a time. 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
Quadraphonic Stereo was a system that was conceptually very similar to SQ, but developed independently by engineer Isao Itoh of Sansui. It was freely licensed to record companies but was rarely found on receivers other than Sansui.
Matrix H
Matrix H was a system developed by BBC engineers to carry quadrophonic sound via FM radio in a way that would be compatible with existing mono and stereo receivers. Several quadrophonic programmes were made for Radios 3 and 4, while Radio 1 carried quadrophonic session recordings by various bands.
See also
External links
- Quadraphonic discography (http://members.cox.net/surround/quaddisc/quadindx.htm)
- List of quadraphonic 8-tracks (http://www.8trackheaven.com/quad-tape-list.html)
- Quadraphonic LPs a fraud (http://www25.brinkster.com/ranmath/pages01/frauds.htm)
- Dolby surround (http://electronics.howstuffworks.com/surround-sound4.htm)
- Allpass network shifts 90 degrees over wide frequency range (http://www.maxim-ic.com/appnotes.cfm/appnote_number/112)
- Learning about quadraphonics (http://www.geocities.com/quadaudio/)