Quadraphonics: SQ vs. CD-4

Friday, March 30, 1973

Whether it's the greatest hi-fi innovation since the introduction of stereo or a plot by the electronics industry to make yet more money off the paranoid, technology-conscious consumer, quadraphonic sound has definitely arrived.

The idea of quadraphonic or four-channel sound which surrounds the listener (as opposed to the two front channels of stereo) isn't new. Experimental quad radio broadcasts have been made and contemporary composers have created multi-channel electronic works. Four-track open-reel tapes (which, with their corresponding equipment, make up a phenomenally minute part of the hi-fi market) have also been available for some time.

What the world was waiting for, however, was a mass-produced, readily acceptable method of quadraphonic sound reproduction such as could be met through the medium of the long-playing record. And now there are not one, but two major quad record systems competing for everyone's money. And there are a host of advantages and disadvantages to both.

SQ System

SQ (for Stereo Quadraphonic), the CBS/Sony system, takes four separately recorded or mixed channels, and passes them through an electronic circuit known as an Encoder, which combines the four into two according to a prescribed mathematical relationship. To reproduce the resulting recorded sound, a Decoder is used, which sorts the two channels out into four signals again.

The major disadvantage of SQ is that it is not true four-channel. Because of the way in which the signals are combined, there is overlapping of signals from one speaker to another and, as a result, imprecise separation between channels. To solve this problem, "logic" systems have been introduced to some SQ decoders to make the separation more exact, to make the four-channels more distinct from each other.

A claimed advantage of the SQ system is its compatibility with regular stereo and mono systems, i.e., when played back through non-SQ equipment, none of the sound will be lost. It can be demonstrated, however, that some information from an SQ record disappears when played through normal systems, especially in mono, where at one point the sound almost competely vanishes.

Another advantage for SQ is that since it reduces all the information to two channels, it can be broadcast over existing FM stations, then decoded by the listener to produce four channels. H2>CD-4 System

The other major system, Japan Victor Company's CD-4 (Compatible Discrete 4-Channel) offers true four-channel reproduction, and is admitted by CBS/Sony to be "theoretically" the ideal quad record system. (CBS/Sony, in fact, markets discrete four-channel open-reel tapes.)

JVC's system squeezes four separate channels into the two walls of the conventional LP record groove by some ingenious electronics. The two front channels are recorded like a normal stereo record, with a frequency range up to 15,000 cycles per second. The two other signals, however, are recorded over a high-frequency range of 20,000-45,000 cps using a 30,000 cps signal as a "carrier," similar to FM broadcasting. All these signals are sorted out by a demodulator, which, in combination with an amplifier, directs each of the separate channels (and in this case, they really are separate) to its speaker.

CD-4 records are fully compatible in both mono and stereo, and all signals are reproduced. However, an ordinary record needle, which usually handles up to about 20,000 cps, cannot recover the high frequency signals which are fed to the demodulator, so the CD-4 system requires a special stylus and cartridge. (The demodulator extracts the rear speaker sound obtained in the higher frequencies by subtracting information according to a mathematical formula.)

One claimed disadvantage of JVC's system is that the grooves on the disc have to be wider than normal because of the extra information they contain. Originally it was thought that CD-4 albums would be only able to contain 15 minutes of material per side, but recent developments have boosted this figure to 25 minutes for popular material, 30 minutes for classical (and there are relatively few programs which exceed these limits).

Another problem with CD-4 is that because of the high frequencies' delicate nature, the records have to be cut (a master disc is made from a master tape by means of a machine which cuts a groove into a disc-shaped lacquer) at a speed almost 3 times as slow as regular (and SQ) records, which natually boosts the cost. of production. JVC, however, envisions that the cutting speed will be brought to near normal with developments in cutting equipment in the next year or so.

CD-4 records also have to be cut at a quieter level than regular records in order to accommodate the additional groove information. This process makes the signal-to-noise ratio very low (i.e., the dominance of the source sound ("signal") over any other sound reproduced during playback ("noise") will not be as great with a CD-4 record), However, JVC looks forward to ameliorating this problem in the near future along with that of the cutting speed.

As well, because CD-4's channels are truly separate, FM broadcasting of CD-4 is presently not possible or practical -- four separate FM bands with an overall increased frequency range are required. Several American companies, however, are petitioning the FCC (Federal Communications Commission) with plans for methods as to how CD-4 broadcasting could become not only possible, but compatible with existing FM systems.

Ambient Sound

And what does quad sound like? I recently had demonstrations of both systems and found that my former skepticism about quad reproduction had softened somewhat.

On most classical recordings, quad attempts to reproduce a concert hall situation where sound comes at the listener not only from the front, but by ambient sound reflected from the floors, walls and ceilings. In this manner, the sound of the world's orchestras in their respective concert halls can be faithfully reproduced (though when the system is crammed into a small apartment, there's some question as to how faithful the reproduction will be). Recordings of SQ classical records which had sounded flat and dry when reproduced on stereo equipment took on extra life when played in four-channel.

More interesting, however, were recordings which are designed expressly for the new medium — mainly popular material, but also electronic music and some classical works. I was disappointed in the much-heralded Bernstein/London Symphony Rite of Spring on SQ, recorded with a special quad seating plan for the orchestra. It sounded echoey and mushy. On the other hand, pop selections, with instruments in special locations and zooming around the listener, provided some examples of the potential creativity the medium holds for arrangers (though much of the pop material currently available in quad is pretty banal).


Sonically speaking, the discrete system had the advantage. Discrete tapes of SQ recordings, which could be made into CD-4 discs, when played in comparison with the SQ records, showed much clearer definition not only in sound but in placement of instruments. (Incidentally, Walter Carlos, the man behind the Moog-synthesized Switched-On Bach, last year wrote a letter to Billboard magazine, which claims that the CBS SQ record of this work was "a pale mirror of the quadrasonic master. Worse, the musical balances are irrevocably bastardized so that, at many times, solo lines are obliterated by accompaniment.")

There are, by the way, increasing numbers of quad records available. CBS, in addition to its own Columbia products, is joined by British EMI (with affiliations to Capitol and Angel), Vanguard and Project-3 in marketing SQ discs. CD-4 records emanate from Japan Victor (and hence American RCA Victor), the monster U.S. record conglomerate WEA (Warner Brothers, Elektra, Atlantic), as well as the European companies, Deutsche Grammophon and Philips.

As to which system is the best to buy … well, I'm going to hold on to my stereo for a while yet. There are bugs in both systems which have yet to be ironed out, and price tags of both will correspondingly go down as these problems are solved and quad sales go up.

Naturally, both CBS/Sony and JVC are at each other's throats to get the biggest share of the market. While admitting JVC's system is theoretically the best, Sony/CBS regard their SQ as the most practical system, and that SQ will be number one on the quad market by 1975. (Since SQ equipment and discs preceded CD-4 by some time, there is more SQ material available at present.) JVC, on the other hand, knows its system is technically ideal, and are banking on the appeal of CD-4's perfection to the consumer.

Both companies claim each other's system is the more expensive. JVC, of course, does not make any equipment which will handle SQ; Sony does not make any which will handle CD-4. However, other non-partisan companies are introducing equipment which will handle both.

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