More Speakers, Ordinary and Extraordinary (Vol. 2, No. 3, Spring - Fall 1980)

By the Staff of The Audio Critic

The interest this time focuses on electrostatics, especially since the dynamic systems under consideration fall mostly into the pretty-good but-unexciting category.

In this issue we got all our philosophical generalizations about speakers off our chest in the separate feature article on the Fourier 1, the first speaker system designed to the specifications of The Audio Critic. Here we shall proceed without further introduction to the reviews, where any theoretical issue raised by a particular speaker design will be discussed in that context only.

Audio Pro B2-50 3D Gruppen, Stockholm, Sweden; distributed in the U.S.A. by Intersearch Inc., 4720-Q Boston Way, Lanham, MD 20801 . Audio Pro ACE-Bass Subwoofer B2-50, $995 (single unit for summed left and right channels, with built-in amplifier and electronic cross over). Five-year warranty. Tested #94B2J1850S, on loan from distributor.

No one can cheat the laws of physics, but this slick little amplified subwoofer manages to cop a plea. Those laws demand a penalty for compact size in a low-frequency speaker--loss of the deepest bass or loss of efficiency or a combination of both. The Audio Pro B2-50, by using every dodge and stratagem in the book, squeezes a fair amount of flat-to-20-Hz bass out of two 62" Philips drivers in a 50-liter vented enclosure, which is small enough to fit into a 1Y2-foot cube that also contains the rather sizable electron ics. The tricks employed include 6th-order Butterworth alignment, negative output resistance in the amplifier, plus a few other little tweaks and massages, the sum total of which is called ACE-Bass (Amplifier Controlled Euphonic Bass) and has been found sufficiently different by the patent examiner to carry a patent.

Our measurements confirmed the 6th-order Butter worth tuning and the claimed f; (-3 dB frequency) of 20 Hz; on the other hand, we measured THD in the range of 4% to 12%, depending on frequency and output level, instead of the 0.6% to 4% range indicated as ''typical'' in the spec sheet. We don't want to make too much of this discrepancy; differences in methodology may be the whole explanation.

The response to a step function (dynamic Q) was found to be typical of a properly damped vented system of this type.

The bottom line in woofer performance, however, is large-signal capability, which is totally independent of how the system Q and the f; are obtained. Piston area and linear excursion are the name of the game when it comes to moving air, and from that standpoint the two 62" drivers are barely equivalent to a single 8" unit and significantly less capable than one good 10-incher. Yes, the B2-50 will pro duce a sound pressure level of 100 dB at 1 meter as specified, but don't forget that 100 dB at 20 Hz is subjectively only as loud as 60 dB at 1 kHz-it's very far from real-world peak SPL's. Even at 40 Hz, 100 dB corresponds to only 84 dB at 1 kHz, which is still not a symphonic level.

To gain the upper hand against the inexorable mathematics of the Thiele/Small vented-box alignments, the large-signal considerations and the Robinson-Dadson equal-loudness curves, it's preferable to opt for a somewhat higher f; (say 34 or 35 Hz) and to start with as large a driver as possible (probably with a 10" unit in a system of this size). It's our impression that the extra design flexibility added by the ACE-bass concept turned the B2-50 into a virtuoso exercise in numbers (20 Hz, 100 dB, 2 times 62", 50 liters, etc.- see, it can be done!) rather than an optimum trade-off between size, price and useful bass.

Which brings us to the nub of the matter-how the B2-50 sounds. Despite the remarkable ability of that itty bitty cube to reproduce the lowest organ and double-bass fundamentals with good definition at moderate levels, the really big passages with deep bass are lacking in authority.

The feeling of unstrained power is missing. We hear distortions when the bottom octave gets really busy that aren't even explained by our higher THD readings. Air turbulence in the vent may be one of the contributing factors, but the main problem is undoubtedly the limited air-moving capability of those two little drivers. They just run out of breath at some point. We feel that the relatively high price of the B2-50 is justifiable only in installations where space saving has top priority, over and above performance per dollar.

We must add that an earlier sample we looked at had a horrendous electronic crossover which completely messed up the sound of the high-pass channels. The more recent sample with the serial number noted above had a revised crossover that sounded quite transparent. Make sure you consider the revised version only.

Editor's Note: The follow-up report on the Beveridge System 3 should have appeared here, as promised in the last 'issue. Unfortunately, our ''improved'' samples arrived much too late and then were further modified in situ by a factory representative at the end of October (new woofers were substituted), so that at press time we're barely familiar with the capabilities of the revised system. A detailed second review appears to be in order and will be included in one of the earliest issues of our forthcoming biweekly Bulletins.

Dalco SW-3 Dalco Speaker Works, Second and Westmoreland Streets, Philadelphia, PA 19140. SW-3 3-Way 10" System, $398 the pair. Tested #4197 and #4292, on loan from manufacturer.

This company once had a tie-in with Dynaco, and it's actually Dynaco's former head of speaker design who is responsible for engineering the relatively new Dalco line, of which this model is a representative sample. In other words, Dalco does have some credentials in the audiophile market.

This medium-sized 3-way acoustic suspension system sounds reasonably musical (or shall we say inoffensive?), but the midrange has an ever-present signature-a hollow and somewhat nasal quality that gives it an unmistakably false coloration. The explanation is readily at hand, since the midrange driver is out of phase with the woofer and the tweeter. We've never seen a case of that (woofer plus, midrange minus, tweeter plus) without precisely the same sonic problems. The speaker is by definition incapable of replicating a pulse, regardless of width, and tone bursts show bizarre interference patterns created by the incoherent multiple wave launch. Furthermore, the woofer is some what underdamped (dynamic Q approximately 1.3, with 3 dB ripple in bass response), although the overall amplitude response profile is very smooth (+-3 dB from 40 Hz to 20 kHz).

On the whole, the SW-3 is far from the hopeless sounding mess most speakers are in this price range; its top end is quite decent, the bass fairly good but not great, the midrange wrong but tolerable. More than that we can't say for it.

Dayton Wright XG-10 Leigh Instruments Limited, Audio and Power Division, 350 Weber Street North, Waterloo, Ont., Canada N2J 4E3. North American distribution by Odin Studios Limited, 7321 Victoria Park Avenue, Unit 2, Markham, Ont., Canada L3R 2Z8. Dayton Wright XG-10 Electrostatic Loudspeaker System, $3499 the pair (complete with IM 10 matching transformer and bias supply, speaker stands, trans former stand). Three-year warranty. Tested #9I09A/B, with 9HO5C transformer, on loan from distributor.

Editor's Note: This review barely missed our last issue; had the speakers arrived just six or seven weeks earlier, we could have completed the tests in time. As a result, the information that follows is a number of months old as of press time, but no less true than it was when new. Mean while the XG-10 appears to have been discontinued after a very short life span; however, there must still be quite a few of them in the stores and more in the always active audiophile secondhand market.

EE The XG-10 was supposed to be the model in which Leigh Instruments would get its Dayton Wright act together and put to corrective use all the lessons learned from the XG-8 Mk 3 fiasco. Well, it didn't quite turn out that way.

This is still a highly inaccurate speaker, riddled with engineering errors.

One thing that has been improved to some extent is the frequency response. After the electrostatic cells had been allowed to charge up over a period of more than two months, a Dayton Wright dealer set up and trimmed in the speakers in our listening room, exactly as they would have been in the case of a regular customer. The trimming-in process involves some fiddling with a variable resistor in each channel of the transformer/bias unit; moderate changes in the spectral balance of the system can be effected that way. Afterwards our own measurements showed that the dealer had done a good job, considering the general orneriness of the XG-10. Overall amplitude response was flat within +5 dB from 90 Hz to 36 kHz, with the piezoelectric tweeter switched in. The electrostatic cells alone, because of the inherent peculiarities of the Dayton Wright design, roll off rapidly above 8 kHz. The peak that used to be at 700 Hz in the XG-8 Mk 3 is now at approximately 600 Hz (so what else is new?); its amplitude is still 7 dB with respect to the trough that follows it. Bass response is worse than before, with a 12 dB peak at 50 Hz and a bottomless dive below that frequency, reaching the -3 dB point at 40 Hz on its way to nowhere. Even granting the mysteries of the dipole/room interface, that's an unacceptable profile.

But the frequency domain provides only very small clues to the essential perversity of the XG-10. Time domain tests with pulses and tone bursts reveal energy-storage problems to make your hair stand on end. This speaker rings endlessly at just about every frequency. There appears to be simply no control to shut off the acoustical output after the electrical input stops. The bass is especially uncontrolled, with an almost infinite series of ripples in response to a step function. Pulses of shorter duration are reproduced coherently, as one would expect of in-phase electrostatic cells, but the trailing garbage after pulse turnoff is gross beyond all expectations. Furthermore, the piezoelectric tweeter is in the wrong acoustic plane with respect to the electrostatic cells-the coherence is destroyed when the tweeter is switched in. Even the small amplitude response squiggles look totally different in the tweeter's range than in the electrostatic passband; they show an abrupt change in signature. This is the worst case of tweeter mismatch we've seen in the course of our laboratory tests so far.

The sound? Little or no bass and inaccurate what there is of it; highs quite unpleasant with the piezoelectric unit switched in. Used as a midrange panel in a tri-amped system (6-dB-per-octave roll-off above 3 kHz provided by special switch position), the XG-10 at least has the attack and large-source wave launch that give any electrostatic a certain authority, but the lack of focus and the unmistakably colored tonality make it a poor choice overall, especially at the price. Quite frankly, we find the cult following of Dayton Wright speakers utterly incomprehensible. Even if it's our own irredeemable aural turpitude that prevents us from yielding to a higher truth, the spectrum analyzer, oscilloscope and B&K microphones are too dumb to lie.

DCM QED

DCM Corporation, 670 Airport Boulevard, Ann Arbor, MI 48104.

QED floor-standing loudspeaker, $480 the pair. Five-year warranty. Tested #4742 and #4743, on loan from manufacturer.

Historically, this neat little 3-foot high column speaker preceded the Time Window as a finished design, but DCM never really pushed it and it ended up as their junior product. That status isn't entirely deserved, as the QED is in some ways a more neutral and therefore more accurate speaker than the Time Window, although it doesn't have the latter's dispersion characteristics or power handling capability. That's mainly because the QED has only one woofer and one tweeter, against the Time Window's two and two. On the other hand, the QED is considerably less colored in the lower midrange, where even the best version of the Time Window exhibits a certain thick ness. In fact, the QED approaches the Vandersteen IIA in overall neutrality and transparency, though we still prefer the latter on all counts.

Our measurements showed very smooth amplitude response all the way up to 20 kHz, with the midrange particularly flat; the - 3 dB frequency on the bottom end is 48 Hz. The tweeter cuts in at about 1.7 kHz and appears to be at full passband level at 1.8 kHz-that's pushing a 1" dome to the limit, we'd say. Above 20 kHz the tweeter response drops like a brick. The vented box is tuned to 40 Hz and the maximum output from the vent is at approximately 50 Hz, constituting a surprisingly Thiele/Small-ish alignment for DCM, whose other enclosure designs march to a different drummer.

As in the Time Window, the tweeter is connected out of phase, and again DCM almost gets away with it, owing to the driver spacing and the nature of the crossover net work. Thus, despite the polarity reversal, pulse replication is good down to a width of 0.2 msec, but with the inevitable opposite-going preshoot also observable in the Time Window. Tone bursts are quite accurately reproduced, indicating freedom from significant ringing throughout the speaker's frequency range. The response to a step function (dynamic Q) shows essentially correct damping in the bass.

We're very favorably impressed with the clean, musical, relatively uncolored and nicely balanced sound of the QED, although you can't play it as loud as the Time Window. Since a pair of QED's costs $180 less, and since we have some reasons to suspect a slight decline in the sonic quality of recently produced Time Windows, we now consider the QED to be the best per-dollar value in inexpensive audiophile-oriented speakers.

DCM 'Time Bass' DCM Corporation, 670 Airport Boulevard, Ann Arbor, MI 48104.

'Time Bass' woofer system, $770 the pair. Five-year warranty.

Tested #500 and #501, on loan from manufacturer.

Imagine a slightly less tall and very much fatter Time Window, and you have a fair idea of what the Time Bass looks like. It's far from a small woofer, so you expect it to have really deep and powerful bass. It doesn't quite meet that expectation.

This is one of those vented designs in which the vent is so small that it doesn't seem to make much sense. The loading conditions are such that with a large input voltage the vent is unable to handle the required output and, as a result, modulates the bass. The response to a step function clearly shows that the dynamic Q varies all over the place, depending on drive level. The box is tuned to 12 Hz, an impossibly low frequency by any criterion, and the fj (frequency of the lower of the two impedance peaks characteristic of vented designs, i.e., the point of maximum sensitivity to subsonic excitation) is an incredible 7 Hz.

That's living dangerously. Under small-signal conditions the frequency response is reasonably flat, with the f3 (-3 dB point) at 32 Hz, but on organ music and other high-energy program material containing powerful low-frequency fundamentals the Time Bass lacks the authority and visceral impact of a really good 32-Hz system. It just doesn't audibly play low enough, clean enough and tight enough.

Of course, if you ask DCM, they'll tell you that the Time Bass, with its highly versatile adjustable passive crossover, was designed primarily for flexibility of placement and proper blending with satellite speakers. Nothing wrong with that, but what good is a perfect blender if your eggnog doesn't have enough rum in it? Genesis 2+ Genesis Physics Corporation, Newington Park, Newington, NH 03801.

G2 + floor-standing 2-way speaker system, $598 the pair.

Lifetime warranty (to original owner). Tested #12562 and #12568, on loan from manufacturer.

For the money, this is quite a well-built speaker, made with parts of good quality. It consists of a 1" inverted dome phenolic tweeter (a Winslow Burhoe design we don't particularly care for), an 8" woofer and a 10" passive radiator, in a fairly compact cabinet that stands a little under three feet tall. The tweeter is wired out of phase with the woofer, cuts in at approximately 2 kHz, and exhibits a relative rise of 6 dB (as referenced to the midband) as it goes up to 20 kHz and then plummets like a stone. This treble-boosted response, which persists even with the tweeter switch in the ''decrease'' position, is the worst feature of the G2 +, resulting in an overly aggressive, fatiguing top end. Too bad, since otherwise the speaker has some outstanding qualities.

The midrange is exceptionally transparent and uncolored, more so than the Vandersteen's or either DCM model's. The bass is also the deepest and best-controlled of that crowd, thanks to the almost perfect 4th-order Butterworth alignment (box tuned to 31 Hz, -3 dB response at 32 Hz).

In fact, below the 8" woofer's natural roll-off at approximately 1.8 kHz, this is as good a ''cheap'' speaker as we've tested so far-very nice indeed. Whatever we don't like about it is all in the tweeter's range.

In the time domain, tone bursts reveal no serious ringing anywhere; pulse replication is necessarily quite imperfect as a consequence of the polarity reversal between the two drivers, although a fudged pulse a la DCM is obtainable down to a width of 0.15 msec. The dynamic Q of the woofer/radiator system is in the ball park for a 4th-order Butterworth and remains stable with increasing drive.

Overall, if we hadn't found the top end objectionable, the Genesis 2+ would have come out on top in our search for the best speaker per dollar in the middle hundreds, but under the circumstances we can't make that recommendation.

Mariah LS-1

Mariah Acoustics, Route 28, Arkville, NY 12406.

LS-1 floor standing speaker system, $1395 the pair. Three-year warranty. Tested #155 and #156, on loan from manufacturer.

This 44-inch high truncated pyramid looks like an Ohm F but is actually more like a Snell Type A in concept, with a 10" downward-facing woofer in a sealed enclosure, 4" midrange and 1" dome tweeter. The polarity of these three drivers in the system is plus/minus/plus respectively, the worst possible phase relationship as we've had occasion to explain before. The inevitable midrange hollowness that results is one of the immediately audible signatures of the speaker.

Another is the rather hard and fatiguing treble range, perhaps not to be blamed entirely on the known shortcomings of the Peerless tweeter used, since the measured amplitude response happened to be dead flat to 17 kHz and -3 dB at 20 kHz. The problem may very well be in the upper midrange, where we had reason to suspect some FM riding on the sine wave test signal in the vicinity of 2 kHz. Our suspicion was strengthened by the audibly ''dirty'' character of the sine wave output. This is just conjecture, but the unpleasantly nasal and cutting quality of the speaker on musical program material is not.

The bass seems strangely weak, even though the measured response shows the -3 dB point to be at 38 Hz, a reasonably low frequency. It's possible that, with the woofer facing the floor, the loading conditions are optimum only when the speaker is pushed all the way against the back wall, an inconvenient position in our listening setup. Of course, a 10" driver without the aid of a vent necessarily has somewhat limited air-moving capability. Our dynamic Q test shows the sealed system to be slightly underdamped; the Q appears to be just a little over 1 but at least stays there regardless of drive level.

Pulse replication is once again out of the question with the midrange pulling when the woofer and tweeter are pushing; in addition there seems to be an appreciable amount of time smear when the speaker is pulsed, stretching the original transient event to more than 10 times its length.

Tone bursts evoke no egregious ring patterns, but some very odd waveform outputs are observable as a result of the tweeter/midrange wave-launch peculiarities.

We also have some serious doubts about the use of very light fuses to protect each driver in the LS-1 (woofer 12 amps, midrange ¥%, tweeter 2). Some of the audible effects discussed above may be at least partly due to the nonlinearities of such fuses under dynamic conditions. All in all, our conclusion is that the Mariah needs considerable reengineering before it can become a serious contender in its price category.

Mordaunt-Short 'Pageant Series 2'

Mordaunt-Short Inc., 1919 Middle Country Road, Centereach, NY 11720. Pageant Series 2 loudspeaker system, $545 the pair. Five-year warranty. Tested #15235, on loan from manufacturer.

Made in England and imported as well as distributed by a U.S. company of the same name formed for that purpose alone, this is a 2-way system built around an excellent 8" bass/midrange driver and a somewhat questionable 1" dome tweeter. The vented box is of approximately one cubic foot internal volume.

To start on the bottom end, the box is tuned to 34 Hz and maximum vent output is at 54 Hz-not exactly a text book-perfect alignment. The f3 (- 3 dB frequency) is 40 Hz, but there's some confusion as to the 0 dB reference level in the speaker's response because of a ''valley'' that centers on 500 Hz and dips to - 7 dB there. The vent is once again so small that under increasing drive it starts to crepitate (to put it politely) within its own passband, namely at 40 Hz.

Stuffing up the vent actually gives this particular system better power handling and raises the f5 to only 44 Hz, while lowering the dynamic Q to a very respectable 0.9 or so. We must admit, however, that in the kilohertz range the 8" unit has beautifully peak-free response right up to its mass reactance roll-off.

The tweeter is another story. Crossed over at a nominal 3.5 kHz, it reaches full passband level at 4 kHz and then does a strange rising number all the way up to 10 kHz, where the response is + 10 dB as referenced to passband level. After that it just dies; at 15 kHz it's already down to -3 dB. This top-end characteristic is undoubtedly responsible for the rather nasty edge imparted to strings, sopranos and other program material in the treble range, which constitutes the speaker's principal fault.

On top of it, the tweeter is (you guessed it) out of phase with the woofer; however, because of the rather high crossover, the spacing of the drivers and the topology of the network, pulse shape retention is surprisingly excellent down to a width of 0.15 msec. Tone bursts reveal some mild ringing in the woofer, nothing to get excited about, and virtually none in the tweeter.

Aside from the distinctly edgy highs, we found the sound of the Pageant quite coherent, satisfactorily smooth in the midrange, perhaps a bit bass-shy in spectral balance.

Score another one for the good-but-zippy side.

Mordaunt-Short 'Signifer

Mordaunt-Short Inc., 1919 Middle Country Road, Centereach, NY 11720. Signifer 3-way speaker system, $1740 the pair (with stands). Five-year warranty. Tested #25449, on loan from manufacturer.

This is the top of the Mordaunt-Short line, a 3-way system with 12" woofer in a vented box of a little over 2 1/4 cubic feet internal volume. The midrange driver is a 5" unit, the tweeter a 1" dome. Let's state it right up front that this far from inexpensive speaker is not our cup of English tea.

The clubfoot of the Signifer is the midrange driver, an utterly wrongheaded design in our judgment. Its paper cone has virtually zero excursion, operating almost exclusively in the transmission mode instead. The termination is totally inadequate, resulting in inevitable peaks and dips in the unit's passband from 500 Hz to 4 kHz, as well as severe energy hangover when pulsed and peculiarly deformed out put patterns in response to tone bursts. Ugh. The woofer and midrange are in phase; the tweeter is out of phase (i.e., the polarity is plus/plus/minus). In this case, pulse shape replication happens to be absolutely zilch-no pulse. The tweeter in its own way is even more disturbed by a pulse input than the midrange, possibly as a result of destructive crossover interaction. What's more, it rolls off to -6 dB at 20 kHz.

The bass characteristics are also unimpressive. The vented-box alignment appears to be totally unrelated to the Thiele/Small filter models. In fact, the vent serves virtually no purpose. The - 3 dB response (f3) is at approximately 40 Hz; 0 dB level is reached only at 50 Hz. The response to a step function (dynamic Q) is quite good, however. As for the overall spectral balance of the 3-way system, it exhibits a definite rising trend up to the point where the tweeter roll-off starts.

The sonic consequence of all this is raucous, edgy, unpleasant highs, plus a lack of coherence in the overall stereo presentation. Listening fatigue sets in quickly and decisively. Not a very positive experience, we're sorry to say.

Pyramid 'Metronome 3'

Pyramid Loudspeaker Corporation, 131-15 Fowler Avenue, Flushing, NY 11355. Metronome 3 speaker system, $2500 the pair (including stands). Three-year warranty. Tested #1230 and #1231, on loan from manufacturer.

Any review of a Dick Sequerra product must be prefaced with a disclaimer of up-to-dateness. By the time the review goes through the editorial and publishing processes, Dick is very likely to have changed the product, at least slightly. For that very reason, we killed our review of an early (Oct. 1979) version of the Metronome 3, which had been scheduled to appear in the last issue. The version discussed here dates from mid-1980.

This is supposed to be the definitive Sequerra statement on a practical, high-priced but still affordable, heavy but still transportable, one-piece dynamic speaker system that can also play very loud. It incorporates two 8" cone woofers in a sealed box, one 4%" cone midrange driver and a special ''economy'' version of the Pyramid ribbon tweeter.

The pyramid-shaped cabinet is not quite 3 feet tall and comes with an open-frame metal stand to raise it off the floor.

The ribbon tweeter is so vastly superior to just about anything used in conventional dynamic speakers that the listener is immediately disarmed by the smoothness of the Met 3's top end and is inclined to declare, 'This is it!" Unfortunately, after further exposure, it isn't it. Not quite.

The main problem is the lower midrange, which has a definite thickish coloration, incompatible with true transparency. We're thoroughly familiar with the Peerless midrange driver used and have never considered it a particularly accurate unit. Dick Sequerra puts it through some extensive modifications, but they don't help very much. Furthermore, the woofer/midrange/tweeter polarity is plus/plus/minus, which doesn't contribute to coherence. The Met 3 is unable to reproduce a pulse with any degree of integrity. (Interestingly enough, the Oct. 1979 version had all drivers in phase. Can't leave well enough alone?) The bass constitutes a further shortcoming. The -3 dB point (f3) in the low-frequency response is at 55 Hz, which is utterly ridiculous in a costly and ambitious speaker of this type. (We're quite aware of Dick Sequerra rationalization, which puts the burden of infrasonic filtering on the speaker, but believe it's just that-a rationalization after the fact, contradicted by any number of existing woofer de signs.) The sealed-box system is in addition slightly over damped, with a dynamic Q that looks like 0.6 in our step function test. The end result is an unarguably bass-shy quality on organ music, bull fiddles, large bass drum, etc. It's possible that the very latest modification is improved in this respect; we can't be sure, though.

There's little else to report. The ribbon tweeter is dead flat up to 16 kHz and rolls off very gently (6 dB per octave) above that frequency. The radiation characteristics of the total system are such that it's difficult to find a ''sweet spot'' where the overall amplitude response is truly flat. The vertical dispersion of the ribbon is quite poor, but it still sounds better than dome tweeters. We also found two ring points in our tone burst tests: at 5 kHz in the midrange (outside the driver's passband) and 8.1 kHz in the tweeter (not evident in listening).

Our overall reaction to the Met 3 is one of 'yes but.' Yes, we're impressed with the top-end smoothness and the dynamic range, but no, we wouldn't spend $2500 for a speaker that's more colored in the midrange than the Vandersteen IIA, Genesis 2+ or DCM QED and has little or no bass to boot.

Quad Electrostatic Loudspeaker

Acoustical Manufacturing Co. Ltd., Huntingdon, England. Quad Electrostatic Loudspeaker, $1780 the pair. One-year warranty. Tested #51073 and #51090, owned by The Audio Critic.

This all-time classic needs no introduction to any audiophile who knows enough to read equipment reviews at all. It has survived virtually unchanged for a quarter of a century (the manufacturer claims there have been no changes whatsoever, large or small, but we take that with a grain of salt); we, too, keep invoking its name all the time, and yet we never reviewed it. The reason for that was a warp in our perspective: after all, more ''modern'' electro statics were clamoring for attention all the time and, besides, everybody knows that the Quad has no bass and no top end (right?), even if it's fabulously transparent in the midrange. So we kept putting the Quad on a back burner of our critical range, concentrating on the Beveridges, Acoustats, Kosses, Dayton Wrights, Sound-Labs and other head line makers of the electrostatic sector. At the 1980 Summer CES in Chicago, however, we picked up certain clues indicating that a full test of the Quad might turn out to be more interesting than we had believed possible. We purchased a pair (for the fourth time in our audio career!) and now have the following to report.

With the two panels six to seven feet apart (center to center) and angled slightly inward, and with a single auditioner sitting perfectly centered about six to eight feet back from the speakers, nothing-repeat, nothing!-we know of equals the transparency and definition of the Quads. Nothing. The speakers seem to disappear; only the music is left. All other speakers are slightly colored by comparison. (You've got to watch your absolute phase, though; the Quad inverts the polarity of the signal.) There's very little deep bass, to be sure. We measured a bump of 6 dB or so at 48 Hz, below which the response rolls off-and that's the way it sounds, too. The highs are perfect, however, in that one listening position; an add-on tweeter could only ruin them. We measured flat amplitude response on axis up to 30 kHz; off axis the response holds up quite nicely to about 20 kHz. The vertical dispersion and overall power response aren't very good, though; hence the widely assumed need for an extra tweeter such as the Decca or Pyramid ribbon. As for the midrange, it measures flatter than anything we've ever seen in our laboratory. And that's not all. Pulses are reproduced with steep sides and reasonably flat tops down to a width of 60 microseconds, an absolute record measurement in our experience. Ringing? Nowhere, sir, up or down the line, certainly nothing beyond the tiniest anomalies. This is some 1955 speaker. As a matter of fact, we refuse to believe that the current production version isn't considerably improved over the Quads of even the mid-1960's. This is not the sound we remember, but then again we weren't driving them with the Bedini 25/25 and using perfectly aligned MC cartridges with line-contact styli in those days.

Of course, the Quad still isn't the speaker for every body. If you insist on deep bass, forget it, unless you're willing to add subwoofers. If you usually listen with several other people, only one of you will be exposed to the proper sound field. And if you like to play your music at discotheque levels, you won't be happy. The Quad is a rapier, not a broadsword. But, wow, what a blade! Sound-Lab R-1 (follow-up) Sound-Lab Electronics, 5226 South 300 West, Suite 2, Salt Lake City, UT 84107. 'Renaissance Series' R-1 electrostatic loudspeaker, $2795 the pair (without woofers). Tested samples on loan from manufacturer.

Dr. Roger West was kind enough to replace our original samples with a later and slightly improved pair, having somewhat higher output, a marginally lower resonant frequency on the bottom end, and correctly marked input polarity. We haven't changed our high opinion of the sound of the speaker; if anything, the later samples sound even better, more firmly controlled, more buttoned-down.

The new experience, however, was to hear how much the R-1 resembles the Quad in overall tonality, but of course with greater dynamic range, better dispersion, and an audibly larger radiating area. On the other hand, the Quad doesn't suffer from the lobeyness caused by the segmentation of the Sound-Lab's active surface, and you can both measure this and hear it. Pulses from the Quad always look clean, whereas from the R-1 they're either clean or covered with spiky wriggles, depending on the position of the measuring microphone. Move the latter half an inch and the picture changes. The slight hardness we faulted in the R-1's sound is unquestionably due to this anomaly; the Quad sounds just as unquestionably cleaner and more natural.

And that leaves the purist no choice-he must go with the Quad for critical applications (such as equipment reviewing), even though the Sound-Lab is a more practical, less fragile and also very fine speaker.

We understand that Dr. West (who, incidentally, is one of the most knowledgeable audio practitioners we've ever had a dialogue with) is working on a ''seamless'' version of his design, without any latticework. Should this ever become a commercially available model, we have a feeling that all the best electrostatics had better look to their laurels.

There's not much else wrong with the Sound-Lab R-1.

Recommendations The more we learn about speakers and the more speakers we learn about, the less easy it becomes to make unqualified recommendations. We apologize, therefore, for the slight hedging of absolutes in our presentation of these consumer options.

Most transparent and neutral speaker tested so far, regardless of price: Quad (to be biamped with Janis W-1 subwoofer, at your option, for more extended bass).

Alternate to the above, with greater dynamic range: Sound Lab R-1, biamped with Janis W-1 sub woofer.

Best full-range speaker of practical size for the audio purist: Fourier 1 (but see article in this issue to judge our impartiality).

Best value per dollar in a low-priced speaker: DCM QED.

Best tweeter: Pyramid Model T-1.

Best subwoofer: Janis W-1 with Interphase 1A.

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[adapted from TAC, Vol.2, No.3 ]

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Also see:

The News in Power Amplifiers: Mostly Very Good: Amber Series 70 (follow-up) , Bedini Models 25/25 and 45/45 (follow-up) , Denon POA-3000 , JVC M-7050 (follow-up) , The Leach Amp and The Leach Superamp , Sonotron PA-2000

Various audio and high-fidelity magazines