Quadraphonic: The forgotten surround sound of the 70s

Yesterday, when I was writing about the aborted attempt of the music industry to put some kind of copy-protection system into vinyl, I mentioned in passing an old friend of the family, who had hoped that his decoder gizmo to bypass the system would make him rich. He was also the only person I ever encountered with a Quadraphonic sound set-up.

Quadraphonic is the forgotten surround sound system of the 1970s. It was never a huge commercial success, in part because the required equipment was expensive, in part because of myriad conflicting formats, and in part because of the limited availability of any albums apart from those by the Allman Brothers Band in the format.

When I worked in the rarities department at Reckless, we used to automatically get any quadraphonic album that was sold into the stores to sell via mail order. We had a select band of quad-buffs on our mailing list who would basically buy any album in that format. I guess if you've managed to preserve a working quadraphonic set-up, it would be nice to have something new to play on it from time to time - whatever it was.

The competing formats of quadraphonic sound contrived, like the modern day recordable DVD format war, to have almost identical names - CD-4, UD-4, Q4, Quad-8 and my favourites - the completely different QS and SQ systems.

On reel-to-reel cassette or 8-track cartridge it wasn't so hard to provide 4 discrete channels of audio. On vinyl, however, the trick was to encode the four channels into the groove and then use a mathematical matrix formula to decode the four elements of the signal.

That meant extra equipment, carefully set up record players with more sensitive cartridges and stylii, and having to press records on better quality vinyl.

Some of the ideas behind particular versions of quadraphonic seem particularly baffling. The CD-4 format, for example, encoded the information that allowed the 4 tracks to be separated in the inaudible 18 to 50 kHz range. Which would be fine, except for the fact that if you've ever heard the muddy sound of an over-played vinyl record, you'll know that it is the top frequencies that are eroded by play the fastest. The high frequency carrier signal was almost certain to be unreproducable after a half-a-dozen plays of an album, leaving the buyer with a very expensive record with wobbly stereo.

Tab Patterson appears to be the world wide web's leading expert on quadraphonic sound consumer equipment. He has some neat animated gifs illustrating the way decoders split the signal into four.

He also has a great selection of pictures of vintage quad decoders.

It is interesting to note that just being able to split records up into four channels wasn't good enough for most manufacturers - they also had to have some display to illustrate what was going on as well, whether it was VU meters or a Tomorrow People-style visual scope.

Tab's site also has a letter from Cai Campbell suggesting the CD-4 format I rubbished above wasn't all bad:

Here's a bit of trivia for you about CD-4 records. What you say about high-frequency deterioration in vinyl records is true, which is a definite drawback to the CD-4 carrier signal approach. To account for this, JVC invented "super vinyl" which produced stronger, more resilient "walls" in the grooves on the record. All Quadra disc recordings were to be manufactured with this "Super vinyl", but my guess is that not all were (who knows how to tell?) Anyway, this is the same vinyl formula that Mobile Fidelity Sound Lab used for their first Original Master Recording releases! Cool, huh? Anyway, audiophiles love the Quadra disc issues, not necessarily for their quad content, but because of the superior vinyl resulting in superior sound.

I've seen it claimed on the web that Pink Floyd mounted the first quadraphonic concert on May 12th, 1977. That seems a little late to me, given that the format was introduced at the start of the seventies, although I guess the live environment was a complicated arena to master. These days Super Furry Animals are the only band I've ever seen to put a whole surround-sound show on, although I also recall Pet Shop Boys doing some weird quad thing with their track 'Sound Of The Atom Splitting' at Wembley Arena in the 80s during a costume change.

The BBC also apparently dabbled with quadrophonic sound broadcasts on Radio 3 and 4. It seems a Cliff Richard concert was broadcast this way as well. To be honest, I thought that for most of the 70s, pop music on the BBC barely got stereo coverage (Radio 1 was restricted to Medium Wave frequencies then), and the most adventurous thing was the Sight and Sound simulcasts between TV and radio. There are a couple of BBC research papers about quadraphonic sound from the 1970s available for download on the web.

• "The subjective performance of various quadraphonic matrix systems" - November 1974
• "Quadraphony: Developments in Matrix H decoding" - February 1977

Incidentally, the early Red Book specification of the Compact Disc in 1980 suggests that it was originally intended to be able to carry quadraphonic sound:

"Number of channels: 2 and/or 4 simultaneously sampled. In the case of more than two channels the encoder and decoder diagrams have to be adapted."

Tomorrow I'll be looking at another obscure 1970s vinyl format - RCA's Dynaflex.

Posted by Martin Belam, January 2, 2008
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