Sound-Lab A-3 loudspeaker J. Gordon Holt, January 1992
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