CBS's SQ encoding method was one of the two most popular quadraphonic matrix-encoding techniques; the other was QS. SQ, which stands for Stereo-Quadraphonic, emphasized left-right separation and compatibility with stereo. Early SQ decoders provided left to right separation similar to stereo, but practically no separation from front to back. Various attempts to improve the front to rear separation were plagued by audible "pumping" as the main signal shifted from front to back, or back to front.
However, by the late '70s, SQ decoders based on the Tate Directional Enhancement System solved this problem and provided exceptional results. The Audionics Space and Image Composer and the Fosgate Research Tate II, both of which used the Tate System, produced remarkable effects from SQ-encoded recordings. If you have lots of SQ recordings, try to locate one of these models or the Tate II's predecessor, the Fosgate Tetrasound. If you'd like more information about the Tate II, be sure to check the Tate II System articles at my own MCS Review On-Line Reprints.
No SQ decoders that I know of included a QS-decoding mode, but late Sansui QS decoders did include one for SQ. If you're unable to find a Tate System SQ decoder, one of the Sansui units could serve for playing both QS and SQ recordings.
EMI (Angel's parent company) caused quite a splash in the mid-'70s when it announced that it would only release SQ-encoded versions of the recordings it produced in quad; in other words, it would not release separate stereo and quad versions of recordings, as CBS had done for several years. EMI then proceeded to release an enormous number of SQ recordings over the next few years. CBS followed EMI's example shortly but only briefly before abandoning SQ in the late '70s.
Last updated: October 13, 2001