The forerunner of today’s multichannel sound formats, Quadraphonic technology aimed to deliver a new era of audio fidelity by adding two extra speakers to the conventional stereo mix. In the studio, a Quadraphonic performance would be cut into four tracks – one each for front left and right, and rear left and right channels. A dedicated speaker for each channel would then reproduce the sound, cooperatively – or independently – of each other.
The effect was to create a dynamic ‘sound stage’ – complete with directional cues from all sides – that would more closely replicate the way our ears hear sound in the real world. In today’s surround sound nomenclature, Quadraphonic audio would probably be described as ‘4.0 channel surround sound’, though what we have today is substantially better, with more channels, higher fidelity and superior directionality.
Introduced around 1970-71, Quadraphonic audio divided into two main flavours – discrete and matrix. Discrete ‘Quad’ systems required dedicated ‘Quad compatible’ players to pick up the four-track recordings and transmit them to the four speakers. There were a few discrete Quad formats released: Quad-4, Quad-8 and CD-4 (Compatible Discrete-4). Quad-4 needed a special reel-to-reel quarter-inch tape player, Quad-8 a special 8-Track cartridge player, and CD-4 used a specially designed CD-4 turntable.
If you invested in a Quad player and its extra speakers, however, you might not have had much four-channel music to listen to. This is because a Quad recording wasn’t always created for each of the three formats, meaning you might have been locked out of music you wanted. In another strike against discrete Quad, some players could play only Quadraphonic sound, and wouldn’t work at all with stereo recordings.
While quite a few Quadraphonic recordings were made over the 1970s (who could forget The Who’s Quadrophenia), the music industry realised the system would only fly if it was made universally backward compatible with stereo. A standard was needed to squeeze quad recordings down to just two tracks, which could then be played on stereo-compatible devices, and then decoded back into four channels.
This is essentially what matrix Quad sound was all about, and a number of different formats developed that could encode four-channel sound into two channels and then a dedicated decoder box would expand it back for the four speakers at the listener’s end. The downside was that matrix audio quality was never as good as discrete Quad systems because some sound information was lost during the encoding process. Stereo Quadraphic (SQ) from CBS and Quadraphoic Stereo (QS) from Sansui, were two popular matrix formats.
Matrix Quad sound also had other drawbacks. Through a number of engineering limitations, the audible difference between the front and rear channels was quite low – at around 3dB. While attempts were made to increase the levels to around 20dB, these were not perfected until late in the ’70s, and by that time, Quadraphonic’s run at making surround mainstream was all but over.
Restrictive formats, expensive components and the audio limitations of four-track reproduction culminated in the commercial failure of Quadraphonic, but not surround sound per se. A little company working in the same field at the same time learned much from the Quadraphonic experience, and now the multichannel systems championed by Dolby Laboratories are common in the cinemas and living rooms of the world.