Sound-Lab A-3 loudspeaker

J. Gordon Holt, September, 1986

The Sound-Lab electrostatic loudspeakers are legendary. Many serious audiophiles have heard of them, and rumors of their existence abound in audio circles. But, like gnomes, UFOs, and poltergeists, Sound-Lab loudspeakers are sufficiently hard to find that it is sometimes difficult to prove to skeptics that they exist at all. Well, I can now report that they do. As proof of this contention, I can point to the two which are actually occupying solid, tangible space in my listening room at this very moment. I have even taken a photo of them, which will be published along with this report if they leave any sort of an image on the film emulsion. (Many such apparitions do not!)

I have even met, face-to-face, and conversed with, a flesh-and-blood person who lays claim to being the designer of, and the president of the company which manufactures, the Sound-Lab loudspeakers. His name is Roger West, and he too is real.

Seriously, though, for a company which has been making loudspeaker systems for almost eight years, Sound-Lab maintains an extraordinarily low profile. It has never advertised anywhere, almost never submitted products for review to magazines (footnote 1), nor has it exhibited at CES for quite some time now (though their speakers were being used by both Rowland Research and Klyne Audio Arts at the 1986 Summer CES in Chicago). As a result, probably only a few thousand people have even heard of the company, let alone heard its loudspeakers. (After this issue of Stereophile is published, 35,000 people will have heard of Sound-Lab.)

Why such diffidence? Because Sound-Lab sees itself as a small company, staffed by people who believe in the product and take pride in their workmanship, and the Wests would prefer that it stay that way. Actually, I don't blame them; that kind of business, today, is a rare throwback to the dark ages, when running a business was supposed more to be fun than to be profitable.

But Sound-Lab's attitude toward the promotion of their products is so laid-back, it's a wonder they sell any loudspeakers at all. How come they're still in business, after eight years of virtual obscurity? Roger attributes this to the incredible quality of his products, whose owners are allegedly so pleased that they voluntarily promote Sound-Lab speakers among their friends. It's the old build-a-better-mousetrap idea, which seems to make great logical sense, but which has brought failure to almost every manufacturing concern that adopted it as a way of doing business. In my opinion, it is not the quality product that usually succeeds today, but the most flamboyantly hyped product. Roger West does not believe in hype, and as proof of his opposite view, he cites Sound-Lab's eight years of longevity and continued, if sluggish, growth. After having lived with a pair of his A-3 speakers for several weeks now, and scanning my notes for the review I am about to write, I think he should be making some contingency plans to cope with a sudden increase in orders: this review is going to be a rave.

First, though, a brief description of the A-3. It is a full-range push-pull electrostatic with a curved (semi-cylindrical) diaphragm. Unlike another curved-panel electrostatic, the similarly-sized (and $900-lower-priced) MartinLogan Monolith, whose low end crosses over to a 12" cone woofer at 100Hz, the Sound-Lab A-3 is a true full-range electrostatic, spanning the entire audio band down to a claimed 32Hz without the use of a dynamic woofer. Also unlike the Monolith, the A-3's diaphragm is not freely suspended between its four edges to produce a continuous curved surface. Instead, it consists of a number of small, vertically rectangular flat panels, arranged in a 90-degree arc. Each panel measures about 4" wide, and they vary in height from 2.5" to 7". The varying vertical dimension, and varying tensions on the Mylar film diaphragm, cause each radiating panel to resonate at a different frequency; careful choice of those resonant frequencies produces a controlled rise in overall response at low frequencies, which precisely (in theory, at least) compensates for the LF rolloff that normally occurs in a dipole system of this size. (This front/back cancellation effect has been described often enough in these pages that I won't go into it again here.)

The A-3 is large enough to impress, but, with its nicely patina'd walnut trim (with mirror-imaged grain patterns for the skirt strip at the bottom front of each speaker) and curved, horizontally ribbed black grille cloth, too attractive to offend or intimidate. Each speaker weighs 145 lbs, but (thank Heaven!) is equipped with 5 castors, so the speakers are a snap to move around in order to tweak locations and orientation. (Just warn the cleaning lady not to roll them out of the way for vacuuming. Tell her you want to accumulate dust under your loudspeakers.)

The Sound-Lab A-3 is rated at 88dB sensitivity (1W at 400Hz input, 1m from the speaker), but my sample pair didn't even come close to that figure. Assuming the manufacturer's 6-ohm impedance figure to be correct for midrange frequencies, 2.45 volts of input would be equivalent to 1 watt of power. I fed one speaker with a 400Hz 1/3-octave warble tone at that level, and measured the output at 1m from the grille with a General Radio 1565-A SPL meter (tripod-mounted, 70 degrees incident angle, 40" height, C-weighted, Fast). The reading was 76dB, 12dB below the rated efficiency figure! Thus, the 100W minimum recommended power is by no means an overstatement.

Unfortunately, the speakers would not, on low frequency test tones, handle even that much power without strain. With a warbled sinewave centered around 45Hz, both of my samples sounded as if they were starting to bottom out at a mere 94dB—with a measured input power of only 12 watts. On musical material, fortunately, rather than bass tones, there were no signs of audible stress until playback levels reached about 100dB (150W input power). This is just about the minimum volume needed to reproduce symphonic and operatic music at realistic levels, but it was barely adequate for clean reproduction of such very-wide-dynamic range recordings as the JVC Rozhdestvensky Shostakovitch Symphony 15. In other words, the large (+ Series) Acoustat speakers are still the only ones I have found that can handle large amounts of mid-bass energy, let alone the below-40Hz stuff.

Footnote 1: Sound-Lab had a somewhat scarring experience with a review in The Absolute Sound several years ago; the resultant drop in sales led to their extreme caution in seeking reviews.—Larry Archibald



But what does the A-3 sound like when it isn't being stressed? I would liken it to a superb tubed power amplifier. Though not altogether uncolored—no loudspeaker is—its colorations have a strong personal appeal. The sound is rather warm and rich through the low end, rather rotund and gutsy through the lower middle range, and soft and sweet through the high end. Through its entire range it has the incredible transparency and delicacy that I have only, to date, heard from wide-range electrostatics. It is, in short, my kind of loudspeaker.

Because of these predispositions, it does not do well with tubed power amps, including the best I've tried: the Audio Research D-250 II Servo. With that amp, the A-3's low end is overly warm and loose, lacking in extreme bottom, and rather flabby through the midbass. And its highs, although gorgeously smooth, are a bit too sweet.

Of the power amps I have on hand—Conrad Johnson Premier Fives, the Electron Kinetics Eagle 2a, a Perreaux 5150B, an Audio Research D-250 II Servo, and a pair of Threshold SA-1s—the A-3s sound best with the Thresholds. The result is a bit short on infra-LF range and midbass impact, but is otherwise almost impossible to fault—at least on recordings of acoustical instruments. Highs with the SA-1 amplifiers are simply gorgeous: open and detailed, yet amazingly sweet, smooth and delicate—very much like what I hear at those live performances where some audiophiles bitch about lack of high end.

As longtime readers know, my priorities for judging reproduced sound are not exactly those of your average audio perfectionist. (Read JA's editorial in Vol.9 No.5 for a second opinion from another perfectionist.) I value middle-range accuracy above all else, tonal balance second, freedom from distortion third, frequency range fourth, and imaging and soundstaging last. This is why I so frequently disagree with some of my associates' equipment reports, and must remind myself periodically that, among audiophiles, I am viewed as somewhat of a heretic. The Sound-Lab A-3s, however, are the first speakers I have heard in which all such considerations seem somehow irrelevant. They seem, to me anyway, to do everything right—if not perfectly right, then at least so right that I almost feel foolish trying to find anything wrong.

How do I love these? Let me count the ways. First off, they do midrange the way Andersen does windows! Cellos have bite and a marvelously luminous glow, piano bass strings sound just like what they are—high-strung steel wires—and the large brass instruments have an authority and awesome power that I rarely hear outside of the concert hall. For this reason, the A-3 gives an illusion of dynamic range like few speakers systems I have heard. (And those few did not do other things nearly as well as the A-3s.) No instruments are favored over others: all sound very convincingly real. Massed violins are particularly good, having that exceedingly rare mix of sweetness and resinous bite that is the earmark of a truly great upper midrange and high end.

Bass range is deeper than that of most available program material, being subjectively flat to around 35Hz in my listening room, but is a little shy of delineation impact when compared with the best I have heard. The only low end I have had in my house that was clearly superior in extension, impact and detail, was that from the Infinity RS-1B's bass towers, whose overall performance above the LF range is, I feel, far less detailed, transparent, and convincingly real than that of the A-3.

But what about imaging and soundstaging, one area where the RS-1B has remained unsurpassed to date? I've heard more breadth and depth in my listening room from some other systems—the RS-1Bs, for instance—than I get from the A-3s, but I have proven to my own satisfaction, via tapes that I mastered myself, that the Infinities in their previous out-in-the-room location (footnote 2) were exaggerating both spaciousness and depth to some extent. (Since the RS-1Bs were moved closer to the rear wall, both qualities are markedly diminished but are more literally accurate. But who gives a hoot about accuracy, when inaccuracy sounds better!) The A-3s, also positioned near the rear wall, produce about the same breadth and depth as the RS-1Bs, but with much greater transparency.

Imaging from the A-3s is spectacular! With a mono source, the "image" remains tightly bunched between the speakers, with no perceptible wander either with changes of pitch or lateral changes of listening position, and this translates into almost incredible image specificity and stability from stereo sources. This is, in fact, the first electrostatic system I have heard which allows me to move from end to end of my listening sofa to the other (a distance of about two meters) without the "stage" position shifting almost entirely to one speaker and becoming, essentially, monophonic. As you might surmise, there is virtually no vertical venetian-blind effect from the Sound-Lab speakers.

The A-3s are the most perfect embodiment to date of my ideal loudspeaker system. Never in my life have I lived with a speaker that has brought, and continues to bring, as much pleasure, excitement, and satisfaction. In short, I am madly, passionately in love with their sound, and I hereby give notice to Roger West that he is going to have a hell of a hard time prying them loose from me.

Footnote 2: See Vol.9 No.4 p.37.—J. Gordon Holt



Now that I've expressed my feelings about the A-3s, I must add that they are not going to appeal equally to everyone. They do not do well on rock material, lacking both the requisite tartness and aggressiveness to do justice to rock music, and can't produce the kind of sound pressure levels demanded by most rock listeners. And, as I mentioned previously, their soundstaging breadth and depth are not as spectacular, however accurate I feel they may be, as those of some other systems. But give these a clean, honestly miked recording of acoustical instruments, and the A-3s seem to vanish, providing as transparent a window on the music as any I have ever heard, with greater naturalness and tonal accuracy than any other.

Quite unlike the sound—a bit lean and (generally) a bit slow—of such state-of-the-art planar systems as Magnepans and Apogees, the A-3s' sound is rich and extremely agile. (I have not heard the $6600 Apogee system, but I assume that it now embodies the same improvements that have been incorporated into the Duetta, Scintilla, and the new Caliper. Nor have I yet heard the latest incarnation of the MartinLogan Monolith, which was received a couple of weeks ago.)

Mind you, I don't want to give the impression that the A-3s are worth buying. Of course, I believe they are well worth the money, shortcomings notwithstanding—and more, if you consider the fact that you can pay more for less quality than these have to offer. I shouldn't say that in print, however, because if I do, the demand for Sound-Lab A-3s may mushroom, Sound-Lab will have to expand in order to meet the demand, and it will no longer be the cozy little family-and-friends company that it has been ever since its inception.

I view that prospect with very mixed feelings. On the one hand, I sympathize with Mr. West in his desire to avoid the chaos that would result from a drastically increased demand for his speakers—the angry phone calls from frustrated would-be customers, dealer cancellations because of an impossible back-order situation, the disruptive move to larger quarters, the frantic search for additional capital that could not be paid back until all dealers had paid up, and so on. And what if Stereophile were to do what TAS has been known to do: follow a rave review with a complete volte face put-down in the next issue? Sound-Lab could go the way other companies have gone as a result of such a shift in the wind: down the tube.

Then there is the fact that much of the A-3's success as a sound reproducer is due to the careful hand-tuning of its diaphragm resonances—a procedure that, to date, Mrs. West has done herself because she has been unable to train anyone else to do it right. Could Sound-Lab step up production of the A-3s without significant sacrifices in reliability and sample-to-sample consistency? (The fact that other manufacturers of dipole speakers have been able to develop instrumentation to replace individual judgment when tensioning diaphragms does not necessarily mean the same could be done with equal success for Sound-Lab speakers. But I do wonder how hard the Wests have tried—if at all—to devise such instrumentation.)

On the other hand, I am compelled to tell Stereophile readers whose sonic tastes parallel my own that a pair of A-3s may just be the last loudspeaker system they will ever feel the need to buy. I have only heard one other system that did a better job than the A-3 of reproducing the illusion of real, live, unamplified music, and that was the Wilson Audio Specialties WAMM, which sells for roughly eight times the A-3's $5750.

It's my feeling that a pair of A-3s belong in the system of anyone who enjoys the sound of a real live orchestra (or chorus or string quartet or opera or what have you) and can afford the purchase price. But in order to help Sound-Lab remain the kind of company they are now and have expressed the hope of remaining, I shall conclude by saying that the A-3 is one of the worst speakers I have heard, that it's an unconscionable ripoff at the price, and that the Wests aren't going to get the review samples back without a fight.—J. Gordon Holt



J. Gordon Holt wrote again about the Sound-Lab A-3 in June 1988 (Vol.11 No.6):

Although the A-3 has been my reference loudspeaker ever since I reviewed it (Vol.9 No.6), I have never been very happy with its hunger for amplifier power. During my initial tests, I measured 76dB of output at 1 meter, which is about 12dB lower than that of most other audiophile systems.

SL president and chief designer Roger West contends that a conventional sensitivity rating makes no sense for a speaker with a very large radiating area, because its SPL doesn't diminish with distance nearly as rapidly as it does from a system in which the radiating sources are small. He's right. But the fact remains that my early-model A-3 is the only speaker I have used that occasionally runs my Threshold SA-1 power amps into audible overload. (In fact, it turned out that my original observation, that the A-3's diaphragms seemed to bottom-out at 94dB SPL, was incorrect. It was the amplifier that pooped out.)

It was Roger's guess that the power supplies in my A-3s were not putting out a high enough diaphragm-polarizing voltage, and there was evidence that this might be the case. The speaker has a potentiometer on it that varies the polarizing voltage, and this is supposed to be set just below the point where the speaker produces random rustling noises. Full-up, my speakers never produced that rustling, even though my line voltage is around 115V. It seems I wasn't the only A-3 owner unable to get full sensitivity from the system, because Sound-Lab subsequently came up with a revised power supply, having a slightly higher step-up ratio in its polarizing-supply power transformer. Now used in all production A-3s (which now cost $6350/pair), the new power supply is available as a trade-up option for owners of older A-3s for $250 per speaker. A pair of them was shipped to me.

No installation instructions were supplied, but it's my feeling that they should be. Although much of the procedure is pretty much intuitive, some steps weren't. For example, each power-supply module weighs about 40 lbs, but because of the shape of the system, you cannot "dump" the module out of its well after you've removed its fastening bolts. Neither is there anything on top of it that allows you to get a good enough grip to lift it straight out. I found I had to use a small screwdriver to pry up one corner, use a larger one to pry it up more, then prop it up with a screwdriver handle while I lifted the opposite side. It was then possible to get my fingertips under the top plate. But it wouldn't come out.

Lifting one corner, I saw the problem. Three banana plugs protrude from one side of the power-supply board, and these were getting hung up on the underside of the well cutout. I could not reach them to remove them. But if I pushed the module toward the speaker screen and lifted its opposite edge (the edge toward the rear of the system), I was finally able to extricate it enough to reach in and pull out the banana plugs. The clearance was awfully tight, though, I was tempted to just tear the thing out and worry about replacing the plugs later.

Once I found out how the things went in, removing the second module and replacing both with the new ones was easy. The banana plugs and their sockets are color-coded, and—except for a few fastening-screw holes that didn't line up (and could not be persuaded to accept a screw)—the rest of the operation was straightforward.

This time, the polarizing-voltage pots produced the requisite rustling sounds at about 1 o'clock, and were in the quiet zone at around 12. Plenty of reserve!

I had been told to expect a 6dB increase in sensitivity, to 82 SPL; actually, I measured 7dB. This may not look like much, but it is equivalent to a 5-fold increase in amplifier power—having the effect of boosting the SA-1's output to 800Wpc! In theory, this should now allow the system to deliver upward of 105dB of clean output from the SA-1s, and that's the way it worked out, almost.

While the SPL meter was kicking up to 105dB on middle-range program peaks without my hearing anything amiss, the limitation on output level was (as before) at the low end, where occasional clicking was audible at around 100dB, indicating diaphragm bottoming. There was no question now about amplifier overload; their output meters were only registering about -10dB (16W) when the clicking set in. That's 6dB higher LF output than I was able to get from the A-3s before, and 100dB at 40Hz sounds very loud. And a midrange 105dB is much louder than most people will choose to listen.

When I first fired these up, I was not at all sure about their sound quality. It had been two weeks since I had last listened to them, as they had been removed from the room while I was working with the VMPSes and PSBs, but it seemed to me they used to sound richer and less aggressive than they now sounded with the new power supplies. So, I put some pink noise through them at around 70dB level, and let them "break in" for 48 hours. That apparently did the trick. I don't know what might have had to break in, but the sound was now much the way I had remembered it, while being cleaner and more effortless on fortissimos than it used to be. The A-3s still won't blow you out of the room, but with the new power supplies, they're no longer the "wimps" I described in a recent issue.

The upgrade effects a significant improvement to the A-3s' dynamic range, and it's more than worth the cost.—J. Gordon Holt



J. Gordon Holt then wrote about the Sound-Lab A-3 in November 1988 (Vol.11 No.11):

I am combining two followups into one here because both products were involved in one of the worst mistakes I have made in many years of testing: I had two of my reference components upgraded at once.

At a recent show, I had heard the latest version of the Threshold SA-1 driving MartinLogan Statements, and observed that the high end was noticeably improved in quality—sweeter and less dry. I arranged to return mine for updating.

While they were gone, and my reference system would be out of commission for a week or so, I figured that would be an ideal time to install the new power-supply modules Sound-Lab had sent me some weeks previously. After I completed the job, I had no amplifiers on hand whose sound I was familiar enough with to assess the sound of the speakers. All I could tell was that, as claimed, the speakers' sensitivity was now about twice what it used to be (see Vol.11 No.6). A major plus!

When the SA-1s returned from Threshold, I gave them a 24-hour warmup and then auditioned them with the A-3s. The result was not pleasant: a relentless steeliness that no amount of adjustment of anything seemed able to control. Where was this spurious brightness coming from? The upgraded amplifiers or the upgraded speakers? Or both, maybe?

A brief listen to the A-3s with a pair of VTL 300W monoblock power amps seemed to exonerate the speakers. But before I had a chance to check out the SA-1 amplifiers under more controlled conditions, our semi-annual "Recommended Components" had to go to press (see the October issue), so we had no choice but to pull the Thresholds out of Class A and put them into Class K (Products to Watch) until the matter could be resolved.

Subsequent listening with the Thresholds has now qualified them for reinstatement in Class A, but my previous followup caveat—that the SA-1s and A-3s can no longer be recommended for use with one another—was confirmed. The latest SA-1 amplifiers are slightly brighter and more forward than the previous version, which is not in itself a disqualification for a supremely good amplifier. (The Mark Levinson No.23 has much the same brightness.) But the same thing also seems to be the case with the upgraded, higher-sensitivity SA-3 speakers. Again, this does not disqualify them as long as they aren't used in an acoustically bright listening room. But just put these two components together, and watch your ears bleed!

As of now, the A-3s remain my reference speakers for several reasons, not the least of which is that I still love the way they sound—but not with the SA-1s. They do better now with the VTL 300s, although I am still fighting the good fight to try and regain some of the seductive richness that first made me fall in love with the Sound-Labs. (And that was using them with the early SA-1s.) The Thresholds will stay around too, as a second reference amplifier, but only for use with speakers that are a bit reticent through the brightness region.—J. Gordon Holt



J. Gordon Holt's final thoughts on the A-3 appeared in January 1992 (Vol.15 No.1):

I've been madly in love with full-range electrostatic loudspeakers ever since I heard a pair of Janszen (KLH) Model Nines way back in the early 1960s. But I must confess I've been an inconstant lover. Every once in a while I'm seduced by the charms of some hot new dynamic system because it's more efficient, images better, throws a more convincing soundstage, grows goosebumps on my goosebumps, or whatever. But invariably, the fire of my infatuation dwindles down to ashes, and—with a sigh of resignation—I box up the dynamics for shipment back to the manufacturer, and schlepp out the full-range electrostatics again. Each time, it's like going home (see sidebar).

For the past five years, "home" has been the Sound-Lab A-3, a rather large, true full-range design in that every part of its radiating surface carries a full-range signal. To me, this is one of its most appealing virtues. Some so-called full-range electrostatics are actually multi-way speakers, sometimes with different electrostatic elements handing different parts of the audio spectrum, occasionally with all of them sharing the signal's low end but with low-pass filters limiting the upper frequencies to a few vertical arrays or strips. The idea was to minimize treble beaming by relegating the highs to narrower radiating elements, but every such design I can recall seemed to create audible discontinuities in the sound, just as crossover networks tend to do for multi-driver dynamic speakers. (Sound-Lab avoids beaming by using many narrow, vertical diaphragm strips ranged in a curved array.)

Another reason I've been stuck on the A-3 all this time is because it reproduces real musical timbres as convincingly as any audiophile-type speaker I've encountered. I can come home from a concert and—too wound-up for beddy-bye—put on a recording, and not be instantly appalled by the difference. Sure, there's a difference, but it doesn't make me want to crawl into a box and pull the top shut. The resemblance gives me hope about the future of audio.

Then there's the typical electrostatic's quickness and delicacy, which are actually the first things I find myself missing after a couple of weeks with my latest dynamic infatuation. I wouldn't ditch these for anything right now, even if we didn't have the kids to consider (footnote 1).

But before discussing the latest incarnation of the A-3, a brief recap of its previous iterations:

Version the First: My initial review of an A-3 appeared in September 1986 (Vol.9 No.6, p.88). The speaker was manufacturer-rated at 88dB sensitivity, but did not achieve that figure, barely making 76dB instead. With the dual-160W Threshold SA-1 amplifier, the midrange was clean up to an spl of 100dBC, but the system sounded as if it was bottoming-out at levels above 94dB through the midbass range (ca 45Hz). (A question was later raised as to whether my amps were overloading, but their meters were showing -4dB when the bottoming set in.) The overall sound with those amplifiers was described as rich, warm, slightly laid-back, and soft at the top, with an effective lower limit a bit below 40Hz. (The speakers did not sound so good with the tubed amps I tried.)

Imaging specificity was reported as excellent, although I don't recall how far from them I was sitting for the listening tests. (Close listening, which I now prefer in order to minimize room colorations, tends to impair off-axis specificity with most systems. I do not choose to sit with my head in a vise.) Soundstaging was quite good, but not as spectacular as that of some other systems, which may or may not have been exaggerating depth and breadth. The original A-3s were not sufficiently tart or gutsy for rock music, but were great for acoustical material.

Version the Second: As reported in a June 1988 "Follow-Up," a power-supply modification increased the range of available polarizing voltage, boosting the sensitivity by roughly 6dB—equivalent to quadrupling the amplifier power. The SA-3s now produced about 105dB of output through the midrange. Oddly, the mod also increased the speaker's clean output capability at 45Hz to 100dB, and made it sound a little more forward and alive, although it was still by no means a rock system.

Version the Third (The Latest): Four more modifications, introduced late in 1990, involved the addition of hinged side panels or "wings," the use of a higher-voltage insulation in the stator-panel wires, the addition of electrostatic shields to minimize ionization leakage between the high-voltage stator circuits, and the introduction of an ultrasonic (25kHz) polarizing supply instead of a 60Hz one. The idea of the wings is to extend the front-to-back acoustical path, to lower the frequency at which cancellation starts to set in. This has the dual effect of extending the speaker's LF limit and, through increased loading, enhancing its speaker's power-handling ability through the range below 45Hz.

The insulation change allowed a substantial increase in polarizing voltage, providing another 3dB of sensitivity—ostensibly without any increased risk of breakdown. The ultrasonic supply (which of course is rectified before application to the plates) eliminates the possibility of mechanical hum from the interface modules and allows the use of a much smaller polarizing step-up transformer.

Equipment used for this update review included the Proceed CD player, Revox A-77 15ips 2-track tape recorder with original (live) recordings, a Sony PCM-F1 digital recording system, Threshold FET-10L line controller, and the same samples of the Boulder 500AE amplifier (reviewed in October 1991, Vol.14 No.10) that I'd been using with the previous model A-3. Audio interconnects were Monster M-1000s, speaker cables were AudioQuest Greens. Program material ran the gamut, although most of the CDs used were Delos, EMI, and Sheffield orchestral titles.

I had no reason to be surprised by the improvement in the A-3's sound, and I wasn't. Most obvious was the extended bass range, which went from its previous 40Hz effective limit to an astonishing 33Hz, but along with this was also a marked improvement in the system's LF quality. No truly full-range electrostatic I have heard has ever had terribly good bass detail, and previous A-3s were no exception. But the latest A-3 has LF control that rivals that of some of the better direct radiator systems. Yes, I've heard greater authority and better pitch delineation from a number of big dynamic-woofer systems, but the A-3s are now at least comparable to them. You still don't get the feeling that you can "count the cycles," but pitches are clearly distinguishable, and there is real visceral impact from the strike of a bass drum and the pluck of a double-bass string.

The sensitivity increase was not really noticeable, except for the fact that I found myself running the preamp's gain control at somewhat lower settings than previously. Average levels of 103dB are now quite easy to achieve, although a certain feeling of nervous tension on my part at that kind of listening level suggested either that the system might have been at the edge of its output limit or that I was near my limit for spl tolerance. For an acoustical-music listener, 103dB is very loud (footnote 2) and when I'm clocking a live orchestra at the same level, I find myself feeling much the same sensation of edginess.

Otherwise, the improvements were small. The sound was somewhat more transparent, depth was rendered slightly better, and my bat-eared friends tell me the extreme high end sounds smoother and more extended than it did. I do not have a wide enough listening room to use the speakers with their panels fully extended, and had them instead folded backward and slightly outward, but to my amazement, the speakers seemed just as capable of beyond-the-speaker imaging as they'd been before the panels were added. The other thing that seemed unchanged in the latest A-3s is their spectral balance, which remained as natural and musical as that of any system I've heard—at least with the Boulder 500AE amp and Threshold FET-10L line amp.

The latest version of the A-3, with the new supply/interface package and stator wiring, costs $7410. Older A-3s cannot be upgraded, as the wooden enclosure itself has been changed to accommodate the new supply, but you might try negotiating a trade-in with your dealer or, if you bought it direct, with Sound-Lab. The optional wings can be retro'd to any A-3, from the earliest model on, and cost $975 to $1250 depending on finish, including the necessary hardware and the wooden attachment strips for the edges of the speaker panels.

The latest Sound-Lab A-3s are an across-the-board improvement over the preceding ones (footnote 3). These are still my favorite speakers, but even more so now.

Parting Shot: It wasn't until I started auditioning a new pair of dynamic speakers that another advantage of full-range electrostatics impressed itself on me. The dynamics have apparently uncovered a horrific problem in my listening room that I never knew existed. (I've been using the Sound-Labs since I moved into the new house last year.) There is now a 45Hz frequency-response suckout of truly prodigious magnitude, and to date, it has resisted all attempts to get rid of it.

The Listening Room computer program tells me the problem is related to the width of the room, but it also tells me I should have had the same problem with the Sound-Labs. So why didn't I? I'm not sure, but I suspect it has to do with their radiating-area width (footnote 4). The narrower the woofer area, the more specific the woofer locations are, relative to the room's sidewalls, and the more precisely the room's standing-wave patterns would be expected to conform to calculated expectation. The radiator width of each A-3 is almost 3¾ times that of each of the dynamic woofers, which means the A-3s are averaging the lateral standing-wave relationships much more than the dynamics.

Or could it simply be that, since the dipolar A-3s don't radiate to the sides, they aren't exciting the room's lateral standing waves? Possibly, but I'm inclined to doubt it, because both systems generate pronounced pressure zones in the room corners, and since the corners are common to both room dimensions, they should be able to excite standing-wave modes in both directions through the rest of the room.

The review of the new pair of speakers is on hold until I either find a solution or don't.—J. Gordon Holt

Footnote 1: I should reassure the more prissy elements of our readership that this was a joke. Actually, we're just very good friends.—J. Gordon Holt

Footnote 2: The OSHA guideline for hearing safety advises wearing ear protectors if exposure to this level will exceed 1½ hours per day. Note that loud rock is likely to be uniformly loud, while classical music—with its much wider dynamic range—is only maximally loud about 5% of the time, and rarely exceeds 100dB at any audience seat.—J. Gordon Holt

Footnote 3: We understand that the A-3 has been further modified since this review was written. JGH was going to follow up this "Follow-Up" in due course, but nevr actually did so.—John Atkinson

Footnote 4: It is also possible that the speaker's fundamentally high-Q bass tuning adds a degree of boost in the exact region where Gordon experiences a suckout with the flatter dynamic speakers. Sound-Lab's Dr. Roger West points out, however, that his patented "distributed resonance" LF tuning should eliminate any such peak.—John Atkinson



Sidebar 1: Electrostatics Speakers Pro & Con


1) Uniform drive. The entire surface of the diaphragm is driven by the signal, rather than just a small area (footnote 1).

2) Because the diaphragm needs no stiffness, it can be very thin for superb HF transient response, and very limp for freedom from resonances.

3) True full-range designs have no crossover(s). There are no driver transition problems; the sound can be absolutely seamless, top to bottom.

4) Large radiating area is associated with less attenuation of spl with distance, providing a broader listening area.

5) Push-pull operation can yield very low signal distortion.

6) Dipole radiation minimizes first-arrival reflections from side walls.


1) Relatively inefficient; they tend to need scads of amplifier power.

2) Sometimes peculiar impedance characteristic complicates amplifier choice. They often work best with good tube amplifiers.

3) Because of multi-kV polarizing supply and high signal voltages, they can be less reliable than dynamics. Modern designs are extremely durable, but chances of breakdown are nonetheless higher than with dynamic systems.

4) Inherent marked tendency toward treble beaming, but there are ways of minimizing it.

5) Deep bass requires a very large diaphragm. Speakers may be humongous.

6) Large midrange radiating area impairs precision of soundstaging, relative to dynamic minimonitors.—J. Gordon Holt

Footnote 1: Uniform drive needn't result in uniform motion, however.—John Atkinson



Sidebar: Specifications

Description: Full-range curved-diaphragm electrostatic dipole speaker system. HF range control, 3-step LF compensation (+3dB, 0, -3dB at 35Hz). Frequency response: 32Hz-22kHz, ±2dB. Sensitivity: 88dB/W/m. Recommended minimum amplifier power: 100W. Maximum input power: 450W. Impedance: 6 ohms nominal, 4 ohms minimum.
Dimensions: 73" H by 31" W by 9" D (Base extends depth to 19"). Weight: 145 lbs.
Price: $5750/pair (1986). $6350/pair (1988); $7410/pair (1992); no longer available (2003).
Manufacturer: Sound-Lab, 6451 Mountain View Drive, Park City, Utah 84060 (1986-1992). Tel: (435) 658-1341. Fax: (435) 658-1342. Web: (2003).