Speaker Systems, Large and Small: Updates and New Developments (Vol.2, No.1: Winter/Spring 1979)

Speaker Systems, Large and Small: Updates and New Developments --- Beveridge 'System 2SW-1' (follow-up); DCM 'Time Window' Pedestals; Dennesen Model 180 and SW-II; Fried Model C; Fried Model W; Pyramid Model T-1 (Improved) ; Symdex 'Sigma' (Improved) ; Thiel Model 03 (follow-up) ; Vandersteen Model II ; XRT 50 (interim report)

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Other than a new medium-priced speaker of Reference B quality, plus some improvements in existing good designs, we haven't found much this time to get excited about-but maybe that's enough for one go-around.

If you've read the preambles to the speaker surveys in our last three issues, you know pretty much where we stand on the subject of speaker design and evaluation. We have no fresh in sights or important new criteria to add at this point, which is probably a good thing considering the unprecedented amount of theoretical material presented elsewhere in this issue (seminar transcript, stylus article, etc.). At the risk of underestimating our subscribers' attention span, we'll skip the orientation lecture this time and proceed directly to the reviews.

Beveridge 'System 2SW-1' (follow-up)

Harold Beveridge, Inc., 505 East Montecito Street, PO Box 40256, Santa Barbara, CA 93103.

Beveridge Cylindrical Sound System, Model 2SW-1, 87000 the pair (including plug-in direct-drive tube amplifiers, HD sub woofers, solid-state bass amplifiers, electronic cross overs and CM-I control module).

Unlimited warranty on all parts except tubes (one year); five-year warranty on all labor, including sonic updates. Tested system sup plied by manufacturer.

The 2SW-1 is the modified Beveridge sys tem we summarized in our reference issue (Vol. 1, No. 6) without actually having put it through all our tests. Now that we've gone over it we can report that it's essentially the same system as the 2SW as far as sonic performance is concerned, with minor improvements. In other words, it's still the best speaker system from a single manufacturer in our opinion, though not necessarily the best speaker system that can be put together as a hybrid by the technically adept audio enthusiast.

The dynamic headroom of the 2SW-1 still isn't exactly what the doctor ordered, although subjectively it seems ever-so-slightly better than that of the 2SW, which we didn't have side by side for comparison. The extreme highs are still slightly rolled off; the bass, however, has been definitely improved. The woofer Q is now 0.7, as claimed, and stays there with increasing drive; the -3 dB point is 36 Hz; THD is quite low at all bass frequencies, even at fairly high levels. We still can't see, though, why the woofer of a $7000 system shouldn't be flat down to 30 Hz or so, especially since high efficiency isn't a requirement for a good match to the electrostatic main speaker.

As you may have heard, Beveridge is about to come out with a new speaker system utilizing basically the same 6-foot electrostatic transducer and acoustic lens, but with conventional transformer coupling to any power amplifier supplied by the consumer and with two woofers in each of the 6-foot enclosures instead of separate bass commodes. It's our impression that this might turn out to be a more practical and convenient system with perhaps even superior sound. The price will be approximately half that of the 2SW-1.

DCM 'Time Window' Pedestals

R. S. Park Audio Associates, 5 Sunrise Plaza, Valley Stream, NY 11581. DCM Time Window Pedestals, $65 the pair. Tested samples on loan from distributor.

As our original review stated, the DCM Time Window will sound even better when raised off the floor. It's partly the peculiar tuning of the vented bass enclosure, partly the height of the drivers with respect to the listener's ears.

These new pedestals do the job neatly and painlessly. Made of wrought iron and shaped to cradle the curved bottom panel of the Time Window, the pedestals securely elevate the speakers 9 inches above the floor, with audible benefits in airiness and reduced bass whomp.

It must be added that a revised edition of the Time Window has just come out, which we haven't tested yet. It has entirely new bass/mid range drivers, and the result may be a whole new ball game. A review is scheduled for the next issue.

Dennesen Model 180 and SW-II

Dennesen Electrostatics Inc., PO Box 51, Beverly, MA 01915. Model 180 electrostatic/dynamic compact speaker system, $440 the pair. Model SW-II subwoofer to match, $275 each (8550 the pair). Five-year warranty on drivers and crossovers; two-year warranty on power supply and energizers,; customer pays all freight. Tested #2194 and #2195 plus unmarked woofers, on loan from manufacturer.

This is the speaker debut of a young company that appears to us very serious and sincere about good sound. Their avowed intention is to provide satisfaction to highly discriminating audiophiles at dramatically low price. A brave idea, not quite brought to fruition in these speakers.

The basic building block of the Model 180, which is a box speaker only a little over one cubic foot in internal volume, is a round electrostatic tweeter element with a 2.5” diaphragm. By itself, this is a neat little unit; we found it to be quite flat and smooth in nearfield response all the way up to 43 kHz, with little or 38 no ringing. The trouble is that Dennesen uses a cluster of five of these tweeters, deployed in a more or less hemispherical formation, in an at tempt “to achieve a coherent hemispherical wave front resulting in uncanny spatial placement with precise imaging, almost anywhere in your listening room” (it says in the blurb). The concept is shaky both mathematically and in actual practice; you can't synthesize a hemispherical wave front by jamming together five circular clamped radiators with edge effects. There are bound to be some pretty grim interference patterns, and indeed our measurements revealed them in profusion. The semi nearfield frequency response of the cluster is of the +7 dB snaggle-toothed variety as a result, and tone bursts display severe cancellation and reinforcement effects. Add to that the fact that the 8” woofer, which is crossed over at 1250 Hz, is out of phase with the tweeters, and you begin to see that coherence is hardly the word that applies here. Pulses are, of course, irreproducible with the tweeters pushing when the woofer is pulling, especially since the reversal of polarity is plunk in the middle of the passband.

Speaking of that 8” sealed-box woofer of the Model 180, it shows a 4! dB peak at approximately 50 Hz and is rather poorly damped. The Q appears to be in the neighbor hood of 1.75, rising to 2.0 and beyond with in creased drive. Sloppy.

In our listening tests we found the speaker to be hard, bright, sizzly and fatiguing. Since the interference patterns and peakiness are worst right where tweeter cluster first cuts in, from 1.25 kHz to 3 kHz or so, this irritating quality doesn't surprise us; the ear is extremely sensitive in that range. The manufacturer insists that placement of the Model 180 in the room is extremely critical, and that of course is necessarily true wherever reinforcement and cancellation effects dominate; it's like insisting that body placement is extremely critical on a lumpy mattress. How about eliminating the lumps instead? As for the Model SW-II subwoofer, we don't quite see the point in it. It's claimed to be designed specifically to match the Model 180, yet its frequency response doesn't extend appreciably lower, nor is it significantly better damped. We measured +2 dB small-signal response down to 48 Hz and a Q that varied from 0.7 (excellent) to 1.5 (underdamped), depending on the amount of drive. The frequency response was also affected to some degree by the drive, indicating a voice coil that comes out of the gap.

Overall, we're unimpressed by the Dennesen speakers, even though we appreciate this company's recognition of the inherent superiority of the electrostatic principle and of the fact that the high cost of electrostatic speakers isn't a law of nature but a marketing phenomenon that can be altered.

Fried Model C

Fried Products Co., 7616 City Line Avenue, Philadelphia, PA 19151. Model C satellite monitor, $950 the pair (3400 the pair in kit form-everything but the wood). Tested #C1047K and #CI1048K, on loan from manufacturer. This is the top part of Fried's new $4000 plus Super Monitor, which we haven't tested.

As a separate satellite, the Model C is very similar to the B/2 reviewed in the last issue; it has exactly the same dome tweeter, a considerably heftier 6” bass/midrange driver, and a heavier enclosure that tapers toward the top.

It should by all rights sound a little better (take a look at that price!) but it happens to sound considerably worse. We found it very strident and fatiguing, especially nasal and cutting on solo strings, but almost equally unpleasant on most instrumental combinations as well as voices. This assessment proved to be quite shocking when told to a number of people who were familiar with the speaker, so we must con template the outside possibility that something was wrong with our samples. If there was, it was the same defect in both speakers, which would be quite a coincidence.

We believe that the stridency is due to a broad peak in frequency response centering on 3.8 kHz, where the ear is extremely sensitive.

This is one case where the time domain doesn't appear to be the source of the problem, as we found pulse replication quite accurate to 0.2 msec (only the very best speakers make it to 0.1 msec) and saw little or no ringing on tone bursts.

Aside from the somewhat alpine frequency response profile, the greatest peculiarity of the Model C is the pair of 1/2-inch holes drill ed into the otherwise tightly sealed enclosure.

These provide an ineffectual sort of resistive loading that makes the enclosure conform neither to optimized vented-system parameters nor to a pure sealed-box model. It's the worst of both worlds. A.N. Thiele, the man who practically invented the mathematical approach to woofer alignment, has an admonition against this very technique in his classic paper. The result is a mistuned box with bollixed-up damping characteristics; the response to a step function resembles that of a system with a Q of approximately 2.0, but with increased drive the volume velocity through those constricted vents becomes enormous at 100 Hz and below, so that the holes actually whistle and no accurate microphone measurement of any kind can be made. It's quite clear that the woofer Q itself is much too high and those little holes in that little box can only make matters worse instead of better. The fundamental resonance of the sys tem appears to be at approximately 100 Hz, where there's a nice fat hump just as you'd expect. The rationale for all this as presented by Fried Products in their literature is unrelated to any system of physics or mathematics known to us.

Perhaps we're making too much of the poorly controlled bass of the Model C, since it's sonic impact is dominated by the stridency in the treble. In any event, we suggest that its designers listen carefully to the cheaper and less efficient Model B/2 again as a fair example of neutral and uncolored speaker sound.

Fried Model W

Fried Products Co., 7616 City Line Avenue, Philadelphia, PA 19151.Model W three-way speaker system, $640 the pair. Two-year warranty. Tested #2008 and #2009, on loan from manufacturer.

Word had been passed to us just before we received the Model W that we were going to prefer it to the DCM Time Window and probably nominate it as our Reference B speaker.

That turned out to be a rather unsuccessful bit of prophecy but we're mentioning it because it indicates where the manufacturer positions this new 3-way, 2-cubic-foot model.

To us the speaker sounded grotesquely colored, altering some instruments almost be yond recognition both in size and timbre, and giving voices a thick, funky quality, as if the singers and talkers had colds. Our listening tests didn't last very long.

This time the trouble is definitely not in the frequency domain; we measured extremely flat response from 50 Hz all the way up to 20 kHz, with just a very slight and smooth rise at 15 kHz. The problem is in the time domain, beginning with the fact that the 4” midrange driver is out of phase with the 8 woofer and the 1” dome tweeter. This throws two octaves in the middle out of sync with the rest of the spectrum, resulting in severe additive and sub tractive interference patterns on tone bursts and badly impaired pulse replication. This sort of thing is invariably audible and can't be rationalized away.

As in several other Fried systems, there are also bass anomalies. The quasi-third-order vented system appeared to be horrendously underdamped as the speaker was first delivered to us; additional strips of acoustical foam sup plied by the manufacturer changed the picture somewhat. Without the latter, there was an 8 dB hump at 70 Hz (the only interruption of the smooth overall response profile), and a high amplitude step function caused 80 msec of ringing. Ouch. Harmonic distortion increased dramatically from 70 Hz downward. With the extra strips stuffed into the vent, the amplitude of the hump was reduced and the bass response looked more like that of a somewhat under damped sealed box, extending down to about 40 Hz with a Q of approximately 1.5, wandering to higher values with increasing drive. Better, but still far from optimum alignment. You can stuff a turkey but you can't change it into a bird of paradise.

Pyramid Model T-1 (Improved)

Pyramid Loudspeaker Corporation, 131-15 Fowler Avenue, Flushing, NY 11355. Model T-1 Ribbon Tweeter, $1175. Three-year warranty. Tested factory modified samples, owned by The Audio Critic.

The only serious fault of what we called the world's best tweeter in the last issue has been corrected, at least to some degree. The 5 position filter/attenuator has been redesigned, so that it comes much closer to allowing the same frequency response profile in all positions.

We still discern something of an energy-storing, Q-ey hump just past the “corner” of the high pass filter in the 0 and -2 dB positions, but not as elevated as before. In the -4 and -6 dB positions, most likely to match the efficiencies of typical systems, the hump collapses quite satisfactorily, and in the -8 dB position, which will match only very inefficient systems, the response of the tweeter is ruler-flat from. 2.5 kHz to 30 kHz. With a separate level controlled amplifier channel driving the tweeter, it's the -8 dB position we recommend.

Tone bursts elicited no ringing at any frequency in the modified T-1. Actually, by playing around with various networks, it's possible to equalize the response of the tweeter within +2 dB to 43 kHz; with the new factory version we don't really think it's worth the bother. We've also determined that the inherent rise time of the ribbon is of the order of 8 microseconds, which is faster than the human ear. Very few, if any, other tweeters can make that statement; maybe that's why they create the subjective impression of an “aperture loss” next to the Pyramid T-1. For the upper two and a half octaves of the audio spectrum, this remains our standard of excellence.

Symdex 'Sigma' (Improved)

Symdex Corporation, 12 Irving Street, Framingham, MA 01701. 'Sigma' loudspeaker, 3598 the pair. Tested samples on loan from manufacturer.

This highly inefficient little two-way speaker system has a new woofer but hasn't changed a great deal in sound quality-that's about the extent of the news. For the full discussion of the design see our last issue; here we'll discuss only the changes.

The new woofer in the same sealed box appears to result in a higher Q; we measured 1.1 to 1.2 on a dynamic basis, without noticing any tendency this time to migrate to higher values with increasing drive. The slight reduction in damping results in a few more cycles of bottom range; the -3 dB point is now 56 Hz. The overall frequency response of the system is very smooth all the way up to 20 kHz; the “sweet spot” for the best reading has moved closer to the woofer end, it seems. Pulse response is very decent but, interestingly enough, not nearly as excellent as before; tone bursts elicit virtually no ringing or extra cycles anywhere.

The speaker still sounds rather lifeless, constricted and uncomfortable on dynamic program material in a large room, perhaps somewhat less obviously so than in the previous version. We still couldn't live with it as our prime source of music. On the other hand, we must admit and emphasize again that at low levels no other moving-coil speaker system known to us sounds as uncolored and “electro static.” Audio purists in dormitory rooms and other small spaces might find it just perfect for their needs, as long as they use a very good and powerful amplifier to drive it.

Thiel Model 03 (follow-up)

Thiel Audio Products Co., 4158 Georgetown Road, Lexington, KY 40505. Model 03 floor-standing coherent source loudspeaker, 3775 the pair. Tested #0119 and #0120, with equalizer #0059, on loan from manufacturer.

The production Model 03 with the revised midrange arrived only a few weeks after our publication of the “interim report” in the last issue; with slightly better timing this review could have been the original one. Sorry about that. The delay allowed one interesting mis conception about the speaker to come out in the open, however; some of our readers are apparently under the impression that Jim Thiel, the personable young man who designed the Model 03, is none other than A. Neville Thiele, the great Australian investigator of the mathematical analogies between high-pass filters and vented loudspeakers. The fact is that Neville is old enough to be Jim's father and spells his last name differently; the vented bass enclosure of the Model 03 was aligned not by Thiele but by Thiel according to Thiele-and not quite accurately, as we shall see.

The midrange of the final production model is indeed greatly improved; in fact, the overall sonic impression made by the Model 03 is quite favorable, especially on first listening.

Prolonged exposure to it made us conclude, though, that what at first appeared like excel lent clarity and resolution was actually a bit of highlighting zippiness, creating an italicizing effect without revealing ultimate inner detail.

When we put our old standby, the DCM Time Window, next to the Thiel, it became immediately apparent that the latter was less trans parent and balanced in sound, adding some spurious information to the signal at all times.

As for the electronically equalized vented box 10” woofer, there seem to be some problems. Sixth-order Butterworth alignment is claimed, but the Q looks a bit high to us for that to be true; there's a 3 dB elevation centering on 70 Hz and spanning 60 to 100 Hz. The response goes way down, though; the -3 dB frequency is 20 Hz and, since the corner is very sharp with a sixth-order slope, 21 Hz is already up on the 0 dB line. Before you say “Wow!” we must quickly point out that this is in no way like 20 Hz response out of a 50-cubic-foot box with four 15” woofers; it's strictly a small-signal tuning characteristic, and the distortion is very high between 20 and 30 Hz. The lowest tone that looked really clean to us was 38 Hz. When somebody steps on an organ pedal way down there, the result is mostly hash. It would have made more sense to tune that 10” woofer and small box to a higher frequency.

The overall frequency response of the Model 03 is quite flat up to 15 kHz, except for a fairly broad dip centering on approximately 900 Hz. The -3 dB point on the top end is at 20 kHz.

Pulse response looks good, as it should in a speaker claimed to be a “coherent source,” but the solid angle over which pulse shapes are accurately retained is extremely small, so that the coherence is mostly academic. Tone bursts revealed severe interference patterns caused by the lack of physical separation between the “dome tweeter and the midrange driver. At the “sweet spot” everything is fine and dandy, but move the measuring microphone just a hair and there are cancellations and reinforcements all over the place, just as if the drivers were ringing. At 3.6 kHz the midrange is ringing, for real. These effects may very well account for the zippiness we heard.

It also has to be added that the electronic equalizer supplied by Thiel, which must be inserted between the preamp and power amp or into the tape monitor loop for correct woofer response, isn't necessarily an audio component of absolute transparency. That's a minor point, however. We still believe that the Model 03 should be rated as a good speaker system, better than most, but certainly not one of the best.

Vandersteen Model II

Vandersteen Audio, 1018 South Mooney Boulevard, Visalia, CA 93277. Model II floor-standing 3-way speaker system, $860 the pair (3880 east of Denver). Matching 6” high metal stands, $50 the pair. Tested #2638 ana #2639, on loan from manufacturer.

Let's start with a paradox. The Vandersteen Model II is the best-sounding speaker system known to us anywhere near its price and is therefore our new Reference B selection. At the same time we very much disapprove of several aspects of its design-more vehemently so than we might in the case of some other speaker we like less.

Now let's qualify all that. To our ears, the Vandersteen sounds more accurate-meaning smoother, more neutral, more finely detailed-than the DCM Time Window, our previous top choice in this category. On the other hand, we haven't tested the very latest Time Window, which has a new set of bass/midrange drivers and is claimed by DCM to be considerably improved. As for the design flaws of the Vandersteen, without which it would be a truly superior speaker, there are two that bother us in particular. One is that the 2” midrange dome is out of phase with the 1” tweeter dome and the 8 woofer. The other is that the 12” passive radiator in the fourth-order vented bass enclosure doesn't track correctly with the woofer; the system is mistuned. (The active woofer has its null at 42 Hz whereas the passive radiator peaks at 50 Hz-a 19% error.) You can hear both of these defects-the first as a marginal smeariness or tonal confusion, the second as a bit of “woofing up”--but the overall sound of the speaker is still so good that we can't demote it from the head of its class.

Why should that be so? For one thing, the Vandersteen deals very successfully with the problems of diffraction and secondary radiation, by means of an ingenious free-standing, unbaffled mounting of the upper two drivers.

These drivers are, in addition, of high quality, resulting in smooth and reasonably flat response all the way up to 30 kHz, without obvious ringing at any frequency. Below 110 Hz the bass is a little lumpy, however, for the reason already mentioned. We'd say that the nominal bottom of the speaker's range is some where in the upper 40's. Pulse response is, of course, hopelessly messed up by the out-of phase midrange. Luckily, the latter covers almost four octaves, so that it tends to dominate the perceived tonality instead of displacing a narrow piece out of the middle like some other out-of-phase midranges. That might well be the major secret of the speaker-plus the fact that its first-order (6 dB per octave) crossover slopes can't possibly get it into time domain trouble.

Stereo imaging is one of the strongest points of the Vandersteen, probably owing to the non diffractive deployment of the drivers. The image is stable and it's located in back of the speakers as it should be. We must caution you, however, about the extremely broad range of the midrange and tweeter controls. Without a calibrated microphone it isn't easy to find the positions that result in the flattest response. It's a slightly quirky speaker, any way you look at it.

But, unlike so many upper-medium-priced speakers, it does sound like music. Take that from a critic who actually has a deep suspicion of “musicality” as the favorite cop-out of those who lack objective criteria.

XRT 50 (interim report)

The XRT Group, PO Box 8, Route 4, Menomonie, WI 54751.

Model 50 floor-standing 3-way speaker system, 8938 the pair. Tested unnumbered samples, on loan from manufacturer.

At press time we're informed that this small speaker manufacturer is in the process of merging with another company, so that their “future marketing and manufacturing plans are in a state of flux.” Since this particular speaker may therefore still surface somewhere, altered or unaltered, as a new product, it will be useful to summarize its characteristics without going into details.

The vented bass enclosure is claimed to be Thiele-aligned but looks grossly misaligned to us. An active equalization module was originally planned to be a future add-on, which may ex plain the discrepancy. The midrange is out of phase with the woofer and tweeter (here we go again!) and has rather ragged response. The tweeter is excellent, with on-axis response to 35 kHz and very good dispersion up to 12 kHz.

The sound is a bit on the zippy and aggressive side, probably on account of large peaks, valleys, suckouts and interference patterns in the midrange and lower treble. Efficiency and headroom are relatively high; overall construction appears to be of solid quality.

A follow-up review will be published should the XRT 50 become a widely marketed product.

Recommendations

There's only one change here since the last issue but it's an important one, from the DCM Time Window to the Vandersteen Model II.

Note, however, that an allegedly improved version of the Time Window will be reviewed in the next issue.

Best speaker system: Reference A of The Audio Critic (see article on reference systems).

Best speaker system from a single manufacturer: Beveridge System 2SW-1.

Best speaker system per dollar: Vandersteen Model II.

Best tweeter: Pyramid Model T-1.

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

Best subwoofer per dollar: The Bass Mint Model 10/24.

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[adapted from TAC]

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Also see:

A Challenge to All Critics of The Audio Critic

Symmetry ACS-1 -- John Curl's Perfectly Coherent Electronic Crossover

Various audio and high-fidelity magazines