Is Ambisonics the Future of Sound Reproduction?

Scene the First. You are sitting in a concert hall, dead center, row M; the cellist walks on to the stage, sits down and starts to play the prelude to the first of Bach's solo cello suites, that intricate unfolding of a rhapsodic melodic line within the tight framework of an implied chordal structure. Melody, harmony, rhythm—none exist at any one point of time in this most exquisite of Bach's solo instrumental writing, yet the skill of the composer, coupled with the artistry of the musician, allow you to perceive the abstract as reality.

Scene the Second. You walk over to your record deck (or CD player), put on the black (or silver) disc of the first of Bach's cello suites, adjust the replay level, walk back to your chair, sit down, and...well it's not the same as the live experience, is it? The laying down of the musical line is the same, the musician's skill at realizing the composer's intentions is the same (or would be if the hubris of the producer and engineer had not unnecessarily intervened), but in no way do you think that you, the listener, have been transported to the concert hall.

But isn't that the raison d'être of high-fidelity sound reproduction? To allow the walls of your listening room to dissolve, and with them your own concerns, allowing the music to release your soul? Shouldn't the equipment act merely as the neutral pathway to emotional release? Why does it still signally fail to deliver the goods 100%, even with the highest of high-end playback equipment?

In previous essays on this theme in Stereophile, I have looked at ways in which the fundamental recording process too often robs us of any chance of recreating the original soundstage (Vol.9 No.8), and how the measurements thought important by engineers—often because they are the easiest to perform—rarely correlate with equipment problems that destroy the live illusion (Vol.10 No.4). What I would like to discuss here is how the nature of commercial equipment and system design in themselves can compromise the potential for musical enjoyment.

It was something said to me by Cambridge Audio's Stan Curtis which triggered this line of thought. We had been talking about the difficulties of a designer realizing his original engineering thought as a mass-produced "consumer durable." As Laurie Fincham of KEF has said, anyone can make a good-sounding prototype; the engineer's skill is tested when it comes to the consistent and cost-effective reproduction of that prototype, performance intact, on a large scale. Stan had found that the ubiquitous step of laying out a pre- or power amplifier's circuit on a printed circuit board introduced a sometimes surprisingly large degradation in sound quality, even though the circuit was identical to that of the hard-wired "bird's-nest" prototype. The increased complexity of the pcb traces, coupled with the perhaps less-than-optimum dielectric properties of the pcb material itself, and perhaps even the reduction of the circuit's physical realization from three to two dimensions, conspire to rob it of some of its sonic transparency.

Scene the Third. We return to our cellist, by now weaving his magic on the first cello suite's two minuets. Assume that present at the concert is a recording engineer of that rare kind who just wants to capture the sound of the cello intact, placed naturally and coherently within its associated reverberant shroud, and, even more rarely when the recording is destined for commercial release, has had the time to position his (perfect) microphones at that spot in the hall exactly right for capturing the perfect balance between the direct sound from the instrument and its reverberation, without compromising the most musically desirable image perspective. (Those who feel that the recording and reproduction of sound is a science rather than an art should attempt some live recording. All the engineering theory in the world and all the understanding of acoustics only serve to take the recording engineer to the point where his artistic ability can have full rein.)

Putting aside for a moment the complexities of capturing intact the full sphere of ambience enshrouding the listener, also assume that the resultant recording (stored on a perfect storage medium, of course) is conventional stereo. This recording is now transferred both to CD and to LP for domestic replay. Unavoidably, losses in quality occur in both transfers, though whether that to silver is less damaging (as you might hear at an Audio Engineering Society convention) or more so (as you might hear at a gathering of audiophiles) is still open to debate.

Act Two, Scene One. You the listener, wanting to hedge your audiophile bets, buy the cello recording on both media. You run home from the store; being a reader of Stereophile, you want it reproduced in your own room with the utmost fidelity to the music. You pick up the CD first...but wait. If you want that maximum fidelity, then the CD player should be plugged straight into the power amplifier, with the shortest possible interconnects. Try it. I suspect that you will be surprised at the level of transparency you hear from your amp and speakers. The experience is not the same as hearing the cellist live, but it is certainly the best you have heard in your room from CD. And are those really the speakers that you thought to be a little muffled when you auditioned them in the store? Certainly they didn't sound as good there as you had been led to expect from the review in Stereophile.

But the sound is too loud or too soft. No problem: add a passive volume control between the CD player and the amplifier. You would like to be able to play with the balance between the channels? Add a balance control downstream of the volume pot, the two being connected by flying leads fitted with RCA plugs to connect to the CD-player output sockets and the amplifier input sockets.

You suspect that the highs are now a little rolled off, the bass lacks a little drive and, horrors, there is an audible buzz when you dim the listening room lights to produce the best ambiance, along with some 60-cycle hum. Obviously, the CD player's output stage is being asked to work too hard. You add a line-level amplifier stage downstream of the volume and balance pots, perhaps mixing in a little gain so that under-recorded CDs can still be played at an appropriate volume.

You feel that only to have one source is an impediment, FM being particularly good in your area; and what about your collection of open-reel tapes? It is possible to plug and unplug every source every time you want to use it, but that rapidly becomes a pain. No problem. Do away with the flying leads upstream and work up a little concoction of phono sockets and switches. You want to be able to record from CD or tuner and monitor from the tape deck? You want to be able to record from one source while listening to another? Add more switches. You might as well add level meters while you are at it, their input circuitry tapping into the signal at suitable points; suitable, that is, for the conveniences of wiring. And what about a second tape loop so you can insert some signal-processing equipment? Certainly there now seems to be something lacking in the sound. And perhaps those loudspeakers aren't as good as you thought when you first played the Bach CD. How about adding some switching at the power-amplifier output so that you can choose between two different sets of speakers? The same switching could be used to mute both speakers when you want to use headphones.

Act Two, Scene Two. The realization strikes: of course, you're listening to CD! The magazine writers always stress that even when it is very good, CD doesn't approach the sonic purity of analog. You pull the LP of the Bach Cello Suites from the rack—assuming that you still are interested in music and haven't become totally hung up on equipment—and put it on the turntable. Sounds terrible without an RIAA stage. Quiet too. With the exception of units from Threshold, Counterpoint, and The Mod Squad, you can't buy an RIAA stage on its own to feed straight into a power amplifier, so you buy a preamplifier. At least it has all the controls and switching in a single convenient enclosure, with the circuitry mounted on a printed board for ease of manufacture and servicing; you can do away with the bird's nest of sockets and wiring you had interposed between the CD player and power amplifier. And with a real preamplifier, perhaps you can site it farther away from the power amplifier, so you don't have as much walking around before relaxing to the music in your favorite chair.

Well, the sound is OK, you suppose, and it is convenient to be able to modify and route the signal with the minimum fuss. Ah, the Mets are on TV—how about buying one of those high-definition monitors to go between the speakers? Get a sharper image of the Doctor's pitching. Get a videodisc player, too. And a Dolby surround unit.

Funny how listening to music seems to be taking a back seat these days. The intense enjoyment you remember from that Bach recording must have been some kind of one-shot event.

Act the Third. You read about this new kind of surround-sound system called Ambisonics. You snort derisively, having experimented with quadraphonics 15 years ago and found it, particularly SQ, some kind of sick joke. But no, unlike those ill-fated, half-thought-out technologies, Ambisonics is not based on a poorly understood extension of the ideas behind traditional stereo. (Did none of the developers of quadraphonics notice that people may have an ear on either side of their heads but singularly lack the ones on the front and back for the correct decoding of spatial information at the sides?)

Rather, it is based on the idea of recording the three-dimensional soundfield at the microphone position and playing back the appropriate signals from multiple loudspeakers so that that field is synthesized at the listener's ears. All you need is more playback channels—a minimum of three is required, but four would be ideal—with at least four loudspeakers. And all the additional switching and controls that are required. And the Ambisonics decoder box.

Yes, you are dissatisfied with the sound from your system. Obviously, this lack of a three-dimensional soundfield is the root cause of this dissatisfaction, and Ambisonics must be the future of sound reproduction.

Epilogue: Sorry, I don't think so. Or at least not yet. For over ten years now, I have been told that stereo reproduction is not enough, that creating a stereo soundstage between and behind the loudspeakers is all very well, but without the reproduction of the ambience from all directions, to the sides and rear of the listener, it will always be less than the live experience. Of the writers for this magazine, J. Gordon Holt and Bill Sommerwerck could be said to be committed to this philosophy, and they are undoubtedly correct. And equally undoubtedly, Ambisonics is the most promising method yet developed to achieve this goal.

In September 1987 I heard two very good Ambisonics demonstrations—by Minim at the London Heathrow show, and by Nimbus Records and Conrad-Johnson in New York. Yet—and I must stress that this is a personal opinion—I don't think that adding more information to an already flawed playback system is the correct way of putting stereo reproduction to rights. As with our notional listener above, the sound of a true stereo recording played back with what Martin Colloms refers to as the "shortest signal path," the least complex one, can be stunning in its recreation of the musical experience. Add on the necessary circuitry, switching, and cabling to render your system suitably user-friendly, and the stereo reproduction will be compromised.

It is a sonic analog of the Second Law of Thermodynamics: "Everything you add to a playback chain makes the sound worse." "Sonic entropy always increases," says the guru. Only when the sonic transparency offered by very expensive preamplifiers such as the Krell KRS2, Audio Research SP-11, Klyne SK-5A, or Threshold FET 10 (to mention four favored by Stereophile's team of reviewers) filters down to the level of products everyone can afford, including CD players and power amplifiers, will it be time to talk about filling in the full sphere of ambience that existed at the original event. And to judge by JGH's review of the Audio Research SP9 in this issue, there is still a long way to go before that can be taken for granted.

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