Space...the Final Frontier Page 5
Although proper surround reproduction requires a minimum of four loudspeakers, the maximum number of signals that can be delivered to consumers is two: front left and front right. This is as true for video sources as it is for audio-only ones. Home Theater's Dolby Surround channel is "matrixed" (footnote 7) into the stereo front signals as antiphase information, making it sufficiently different from the front-channel information in that it can be separated out by L-R subtraction and routed to the rear speakers. The same process allows us to extract ambience from audio-only recordings.
Because it's the result of countless reflections from the performing space boundaries, hall ambience consists of random-phase energy, and roughly half of this is more or less antiphase energy. The direct sounds of the instruments, however, are predominantly in phase, which means that the L-R subtraction will recover more reverb than front-channel sound. This makes it possible to get ambient surround-sound from almost every stereo recording currently available. In other words, you don't have to wait for the record industry to rediscover surround-sound in order to take advantage today of what it can do for musical realism (footnote 8). The surround signals are already on most of the LPs or CDs you buy; you just need the equipment to reproduce it.
Then there's SQ. SQ was the leading quadraphonic system, espoused by CBS (then Columbia), Vanguard, EMI, and countless small rock and pop labels, and it used a matrixing system similar to Dolby Surround. Hundreds of SQ discs were released during the quad years, many of which have been re-released on CD---usually with their surround encoding intact. Modern decoders will extract it (although they don't put the surround images precisely where they belong), producing even more spectacular surround than straight stereo recordings. Pop SQs often featured instrumental sounds coming from many different directions and sound effects zooming around the listener's head, and these are---I hesitate to use the word in such a serious magazine---FUN (there, I said it) to listen to the way they were intended to sound.
But back to reality. Not everyone responds to realism/neutrality in sound reproduction, because many audiophiles rarely get to hear the "real thing"---ostensibly the standard by which a reproduction is judged. But when those who are familiar with live sound in a large space learn what surround-sound can do for the reproduction of that sound and space, they'll never be satisfied with two channels again. Unfortunately, the average audiophile has a hard time learning this, because "going surround" isn't as simple as merely adding a surround decoder, an additional stereo amp, and two more speakers to an existing stereo system. If your present system has enough warmth to sound natural with large-scale music, it'll sound unnaturally heavy and distant when used in a surround system. This is why so many who claim to have tried surround reproduction have been disappointed (footnote 9).
In most cases, you can't just "try" surround-sound; you have to commit to it---to the point of starting from scratch with non-audiophile front speakers that weren't designed to sound any way except neutral. Under the circumstances, it makes more sense for someone who's curious about surround-sound to listen at length to a system designed for it, like a good home-THX installation. Not that THX-approved loudspeakers are necessarily all that great; indeed, they vary significantly in sound. It's just that their THX-mandated performance specs don't allow for much frequency-response fudging. (There are no minimum-performance standards at all for audiophile loudspeakers.)
Most industry insiders agree that surround reproduction is where music in the home is going (footnote 10). They see the burgeoning home-video surround market as a foot in the door of American homes. Several firms are furiously working on ways of delivering discrete (as opposed to matrixed) surround-sound to consumers using data-reduction techniques, and they'll be actively promoting it for music recording as well as for home-video sound. Dolby Labs has already licensed the manufacture of Pro-Logic chips that incorporate decoders for their cinema digital AC-3 data-reduction system. And others (such as the developers of Digital Theater Sound, first used for Jurassic Park) are almost certainly pursuing the same course, raising genuine concerns about another format war like the one that helped kill quadraphonics.
Discrete surround does have a lot to offer, though---at least for rock recording, because it permits any number of effects to be panned into the rear quadrants without confusing the steering circuits (as can happen with Dolby Surround). But discrete surround is some time in the future; in the meantime, we can enjoy the benefits of 70% of what it'll have to offer.
The two-channel cul de sac
As long as we remain stubbornly committed to two-channel stereo, further advancement in reproduced realism just won't happen. Sure, we can continue indefinitely to tweak what we have now, for a minuscule improvement here and a subtle improvement there. And while such endeavors are worthwhile, it's time we faced the fact that trying to reproduce 3-D space from a 2-D system is ultimately futile. Surround-sound is the only way to do it.
Many audiophiles will resist the change, preferring the comfort of the familiar to the challenge of the new. After all, there are still music lovers who listen in mono, because they judge stereo to be "unmusical." But most two-eared listeners will agree that the world has passed those people by. The same will happen to audiophiles who insist that two channels up front are all they will ever need to reproduce acoustical space.
Footnote 7: Matrixing is the mixing of one or more additional signals into the stereo pair according to a set of mathematical "rules" that define image locations relative to front center in terms of phase angles and amplitude ratios (the matrix). When decoding, the same parameters are used in reverse (de-matrixing) to separate out the extra signals from the stereo pair.
Footnote 8: There are a small number of Dolby Surround music recordings available, the most recent of which is Emerson, Lake & Palmer's Return of the Manticore on Victory, which was specifically engineered for full surround-sound playback. RCA/BMG has also remastered the superb Tomita classical synthesizer transcriptions from the '70s in Dolby Surround using, the booklets say, "Snell Acoustics loudspeakers designed by Kevin Voecks" for monitoring. A cool namecheck for Kevin, who can also be seen sitting at the bar in a final-series episode of Cheers.---JA
Footnote 9: A factor in my own lack of enthusiasm for surround-sound is the lamentable quality of the electronics used in typical surround-sound systems. The only Dolby Pro-Logic devices I have heard so far that seem to be able to process music signals---as opposed to video soundtracks---without inflicting terminal damage are the Proceed PAV and the Meridian 500 Series DSP processor, with the Lexicon CP-3 the best of the rest. (JGH is also a fan of the Fosgate.)---JA
Footnote 10: "...two-channel stereo is a crock. The only reason [we have it] is because the phonograph record...could only contain two channels" Tomlinson Holman of Lucasfilm, in an interview in the 1993 Premier Special Edition of Widescreen Review (footnote 11).
Footnote 11: To which I would respond that the other reason is, at least for a centrally placed, solitary listener---and that's what we are, aren't we, fellas?---two-channel stereo works very well with the minimum hardware and data storage requirements: an elegant practical realization of William of Occam's Famous Razor.---JA