Audio Critic the 17 r schematic

Issue No. 17

Winter 1991-92

Retail price: $7.50

In this issue:

More loudspeaker reviews, including a first look at the remarkable new Win SM-10 Broadcast Monitor.

The promised survey article on the various different

approaches to bass optimization and compact subwoofer design makes its delayed appearance.

Our highly popular expose of the wire/cable scene advances to the brutally simple subject of interconnects.

Reviews of highly advanced multibit D/A processors, Dolby S cassette decks, and a high-end TV monitor.

Plus all our regular columns and features, an expanded

CD review section, and two special reports on the clash

of science and voodoo at an unusual AES convention.

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For subscription information and rates, see inside back cover.

Contents of this issue copyright © 1992 by Critic Publications, Inc. All rights reserved under international and Pan-American copyright conventions. Reproduction in whole or in part is prohibited without the prior written permission of the Publisher. Paraphrasing of product reviews for advertising or other commercial purposes is also prohibited without prior written permission. The Audio Critic will use all available means to prevent or prosecute any such unauthorized use of its material or its name.

The Audio Critic® is an advisory service and technical review for consumers of sophisticated audio equipment. It is published four times a year by Critic Publications, Inc. Any conclusion, rating, recommendation, criticism, or caveat published by The Audio Critic represents the personal findings and judgments of the Editor and the Staff, based only on the equipment available to their scrutiny and on their knowledge of the subject, and is therefore not offered to the reader as an infallible truth nor as an irreversible opinion applying to all extant and forthcoming samples of a particular product. Address all editorial correspondence to The Editor, The Audio Critic, P.O. Box 978, Quakertown, PA 18951.

Editor and Publisher Peter Aczel Contributing Technical Editor David Rich Technical Consultant Steven Norsworthy Cartoonist and Illustrator Tom Aczel Business Manager Bodil Aczel

Issue No. 17 Winter 1991-92

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Contents

Recorded Music

Eliahu Inbal's Berlioz Cycle on Denon By Peter Aczel, Editor and Publisher

58 Recent Classical CD Releases 62 Recent Pop and Jazz CD Releases

Hip Boots Wading through the Mire of Misinformation in the Audio Press

53 HP's editorial reply in The Absolute Sound 54 Vance Dickason in his latest loudspeaker book 54 J. Gordon Holt on push-pull amps in Stereophile

The Wire and Cable Scene: Facts, Fictions, and Frauds Part III

By Peter Aczel, Editor and Publisher

The Blind Misleading the Blind (More about the AES Convention)

By Jeff Corey, Ph.D. Professor of Psychology, C. W. Post College of Long Island University

The 91st Audio Engineering Society Convention; or, The Invasion of the Credibility Snatchers (Special Report)

By Peter Aczel, Editor and Publisher

A 31" TV Monitor/Receiver with Audio Facilities

By Peter Aczel, Editor and Publisher

42 Proton VT-331

A Quick Look at Two Cassette Decks with

Dolby S Noise Reduction

By David A. Rich, Ph.D., Contributing Technical Editor

39 Pioneer Elite CT-93 40 Harman/Kardon TD4800

Four More Multibit D/A Processors

By Peter Aczel, Editor and Publisher

28 Aragon MKIID2A 38 PS Audio Digital Link II 37 EADDSP-7000 38 PS Audio Superlink

How to Squeeze Low Bass from Small Boxes: a Survey of Techniques and Trade-Offs

By Christopher Ambrosini, Ph.D.

In Loudspeakers, Is a Good Big One

Always Better than a Good Little One?

By Peter Aczel, Editor and Publisher

11 Fried Q/4 13 Win SM-10 12 Snell Type B 15 Audio Concepts Sub 1 (late addendum)

Box 978: Letters to the Editor

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Editor/Publisher's Note

Well, what did I tell you? This is the Winter 1991-92 issue and it's still winter as

you're reading this, right? Not exactly early winter, as planned, but winter nonetheless

(the last day of winter being March 19 this year). The previous issue came out in the fall,

and the Spring 1992 issue will likewise be published in the spring, so it appears that this so-called quarterly is now actually on a quarterly schedule—sort of. My plan is to make it a bimonthly (six times a year) as soon as possible, but first we must thoroughly solidify the quarterly timetable.

Regularity is part of professionalism in magazine publishing; unfortunately it doesn't assure professionalism in equipment testing and editorial practice, as exemplified by certain regularly published audio periodicals. My aim is regularity without any compromise in quality and, especially, without shooting from the hip under deadline

pressures. It's hard but not impossible.

* * *

You will notice an emphasis on loudspeakers in this issue, reflecting the priorities of my audio philosophy. I believe that the audiophile who is well-informed about loudspeakers will end up with a much better-sounding system than the hairsplitting amplifier tweak (not to mention the cable cultist and related mystics). Realistic assessments of audio electronics will continue to appear in our pages, but you can expect loudspeakers to receive top billing.

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Box 978

Letters to the Editor

We have many thousands of new subscribers as a result of our recent promotional efforts, and this box is overflowing, mostly with letters of praise from audiophiles to whom The Audio Critic is a new experience. They all seem to have gotten together and agreed on the phrase "a breath of fresh air." Like most love letters, these are heartwarming—thanks!— but editorially uninteresting. Letters printed here may or may not be excerpted at the discretion of the Editor. Ellipsis (...) indicates omission. Address all editorial correspondence to the Editor, The Audio Critic, P.O. Box 978, Quakertown, PA 18951.

The Audio Critic:

I read your recent article "The Wire and Cable Scene: Facts, Fictions, and Frauds, Part II" with interest. While I applaud your attempt to strip away the "snake oil" and pseudotechnical "BS" in an area fraught with it, I would like to offer the following items for your consideration. First, before I start, I would like to say that I do have a very slight commercial interest in well-designed audio/video cables for the studio/home for whatever bias this may bring to my arguments. In addition, I am responsible in my main employment for the design of VLSI devices and leading-edge digital/analog systems for telephony. Second, I would like to say that my points apply only to the measurable issues associated with speaker cable; I will let someone else draw the line between where audiophile perception ends and bats' & dogs' perceptions continue.

Frequency response variations, due to the effect of series resistance and inductance on an amplifier's ability to control its load under small-signal conditions with increasing (audio) frequencies, is just one area of legitimate speaker cable design. Fortunately, lowering the series resistance and inductance is simple, relatively inexpensive, and has no significant drawbacks, provided that the amplifier in question has

adequate phase margin.

Control of a load by the amplifier under large-signal conditions is another important design aspect [1]. Data shows that real-world current requirements for amplifiers and the associated speaker cable can run 3-6 times that required for an equivalent resistive load for multiple-driver loudspeaker systems [2]. The solution again is to lower the series inductance and resistance.

As you point out, ideally an amplifier should appear like an "almost perfect voltage source" to the load. Not only do realworld amplifiers have some finite output impedance, but the speaker cable adds substantially to this impedance. Once again, reducing inductance and resistance are the answer to lowering this impedance. At the same time, reducing this impedance also decreases interface intermodulation distortion in the amplifier [3], [4], [5].

Another widely ignored, measurable problem is the VLF transmitter and antenna loop formed by the amplifier, cable, and load. In a system with the voltage gain involved for phono reproduction, minimizing

the antenna loop area formed by the speaker cable by using short, closely-spaced (low-inductance) cable will definitely produce a measurable improvement [6]. With some commercially available cables, noise

induced into a phono "front end" is only

-45 dBV at the output of the line-level preamplifier!

Maintenance of an amplifier's output common-mode rejection via the use of a cable employing "identical" conductors to connect to each side of the load is also an important issue [7]. This criterion is slightly more difficult to achieve simultaneously with low inductance. Coaxial cables do not have adequately matched conductors unless two runs, physically tied together, are used with the second run having the conductors reversed. In effect, the center conductor of one cable and the shield from the other are wired in parallel to connect to each side of the load; this is sometimes referred to as "reverse biwiring."

Finally, the dielectric and physical characteristics of cable construction are important, as they affect capacitance changes over frequency, level, and vibration. Dielectric issues can be minimized by using a low-dielectric-constant material like DuPont Kapton, polypropylene, or DuPont Teflon. The use of a tight-fitting, fairly rigid cable jacket will further minimize any physical problems like microphonics.

Length, as you stated, is important as it affects each of the areas described above.

While I agree with the intent and some of the substance of both your article and

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Dr. R. A. Greiner's articles, I find them both limited in scope. I also find, given the probable audience and the equipment that they are likely using, that some of your conclusions are oversimplifications, for four reasons. First, commercial cables that perform well (significantly better than zip cord) in most of the respects described above are available, and are inexpensive relative to equipment costs, e.g., Hitachi's coaxial speaker cable, Mogami (Boulder) 2477, and the lower-cost Straight Wire coaxial cables like Teflon 12 (although some of these may not be current model designa-

tions). Second, some users have electronic biamplified systems from which they have endeavored to remove fuses, passive crossover components, and other links that tend to minimize the measurable benefits of better speaker cable, and they may want to know what cables are available that maximize the measured performance of their

systems irrespective of price. Third, many

readers will want to know what some of the valid criteria are, especially in the presence of so much "hype" in this area. Last, via hearsay, I understand that you do not use zip cord, but rather Mogami 2477 (Boulder), so why recommend zip cord to the customers of your periodical?

In closing, I want to wish you continued success and add another accolade for Dr. David Rich's article on CD player technology.

Sincerely yours, David S. Mohler Westminster, CO

References

[1] R. R. Cordell, "A MOSFET Power

Amplifier with Error Correction," Journal of the Audio Engineering Society 32 (January/February 1984): 2-17.

[2] I. Martikainen, A. Varla, and M. Otala, "Input Current Requirements of High-Quality Loudspeaker Systems," pre-

sented at the 73rd Convention of the AES,

Journal of the Audio Engineering Society

(Abstracts) 31 (May 1983): 364 (Preprint

1987).

[3] R. R. Cordell, "Open-Loop Output Impedance and Interface Intermodulation Distortion in Audio Power Amplifiers," presented at the 64th Convention of the AES, Journal of the Audio Engineering So- ciety (Abstracts) 27 (December 1979):

1022 (Preprint 1537).

[4] E. M. Cherry and G. K. Cambrell, "Output Resistance and Intermodulation Distortion of Feedback Amplifiers," Jour- nal of the Audio Engineering Society 30 (April 1982): 178-91.

[5] M. Otala and J. Lammasniemi,

"Intermodulation Distortion in the Amplifier-Loudspeaker Interface," presented at the 59th Convention of the AES, Journal of

the Audio Engineering Society (Abstracts)

26 (May 1978): 382 (Preprint 1336).

[6] D. S. Mohler, "Improving the Amplifier-Loudspeaker Interface," AT&T Bell Labs, Denver Audio Club, September

1989. [7] S. Takahashi and S. Tanaka, "A

Measurement Method of Hum Modulation

Caused by a Loudspeaker's Electromotive Force," presented at the 70th Convention of the AES, Journal of the Audio Engineering

Society (Abstracts) 29 (December 1981):

939-40 (Preprint 1823).

I'm somewhat bewildered by this let-

ter, which is 65% solid science, 20% audio-

phile angst, and 15% cloud-cuckoo-land.

I totally agree with the points refer-

enced with [1] through [5] and [7]. My speaker cable article also shows that minimizing R and L yields the best response, and I favor the shortest possible cable for that reason. I have nothing against your double run of coaxial cable, either, although it's probably overkill. That the speaker cable can be part of an "antenna" that transmits noise into a high-gain lowlevel stage is an interesting idea that I find very plausible even though I never had occasion to deal with it. I note that you reference your own work [6] on this subject.

But "dielectric issues"? Vibration?

Microphonics?In speaker cables? At audio frequencies? Here you cross over into Enid Lumley country—and of course run out of

references. Where are the AES papers on tight-fitting, rigid cable jackets, etc., etc.?

As for my recommendations and what

I personally use, I think you're just quib-

bling. I mentioned zip cord to drive home

the point that for a connection of, say, four feet or so the kind of wire doesn't matter; you could use a wire coat hanger with the

contact points scraped For long runs I did

recommend coaxial cable of sufficient

gauge, just as you do. Yes, I own two long

runs of Mogami Neglex 2477, which I orig-

inally obtained from Boulder (see Issue No.

10, page 22—no hearsay!), but currently I'm using very short lengths of nameless

14-gauge two-conductor cable. None of the

above is politically correct to uptight high-

enders, of course, but that shouldn't bother

a technologist like you. Lastly, I don't quite

understand your points about maximizing

"the measured performance" and about "the valid criteria"—didn't my article ad-

dress exactly those issues?

Maybe a more detailed explanation of

your "very slight commercial interest"

would shed some light on the strange incongruities of your letter. In any event, thank you for the positive comments.

—Ed.

The Audio Critic:

I got a real kick out of your article on p. 51 [of Issue No. 16], "The Wire and Cable Scene: Facts, Fictions, and Frauds, Part II."...It took some guts to write that. It won't make you many friends; neither the highfalutin cable manufacturers nor the customers whose illusions you smashed will like you for it.

Oh yes, in thumbing through, I just came across "Hip Boots," where you dumped on George Tice. Great job! I agree with you totally on both speaker cables and

injecting clock pulses into the line. We use 18-gauge zip cord (lamp cord) between our amps and speakers. By the way, I have a graduate degree in electronics, an MS in EE.

One point I would like to emphasize,

though—there is no $1200 amp that can

drive some of the more difficult speakers, like the big Apogees, Infinities, Duntechs, etc. For this you need a $6000 amp. The

$1200 amp would go up in smoke.

Now you may say, "Who needs these monster speakers? A smaller, dynamic, high-efficiency speaker is good enough." Maybe—that is a subjective judgment. But the big speakers exist; a lot of people like them; and it takes an amp with a lot of balls to drive them.

Sincerely, Jack Jones President NRG Control, Inc. Walled Lake, MI

P.S. In our power amps we developed our own low-inductance cable to prevent ringing and instability. Low inductance is the key. We could not find anything satisfactory on the market.

I didn't "dump" on George Tice; I

criticized, and protested against, the way

he dumps his stuff on gullible audiophiles.

As for amplifiers, do you think the

Adcom GFA-585 ($1200), the Carver

TFM-45 ($949), or the Hafler XL-600 ($1299) "would go up in smoke" driving any speaker that doesn't drop below 2 ohms impedance at any frequency? I don't think so. And that covers the great majority of the monster speakers.

Your need for exceptionally lowinductance cable in your power amplifiers is due to their 1 MHz bandwidth. I'd like to

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be shown that, say, 100 kHz is insufficient. I suspect that in this case one excess begets another.

Thanks for the compliment.

—Ed

The Audio Critic:

...The overall approach of your reviews appeals to me. I just can't be convinced that interconnects costing hundreds of dollars can make huge improvements in the sound. Otherwise, simple receivers should have a significant advantage over costly separates.

Thanks, Richard L. Brown West Hartford, CT

Very good point. Nothing can possibly

be lower in distortion/coloration than hardwiring over a couple of centimeters without any transmission cable. In a receiver, the tuner section is directly wired in this manner into the preamplifier/control section, which in turn is similarly wired into the

power-amplifier section. Therefore, as far

as line-level connections are concerned— and nothing else—a receiver beats highend separates hooked up with high-end interconnects because no cable can be quite as good as no cable at all.

—Ed

The Audio Critic:

Thank you for the issue [No. 16] of

The Audio Critic. I couldn't put it down on my train ride...to New Haven! The quality and depth of the reviews were superb, the humor poignant. If George Tice meets your challenge I would check the credentials of his supporters very closely! I've read his "white paper" with some astonishment that

he has the chutzpah to put so much garbage

into print.

I especially liked your speaker cable

simulations, for obvious reasons. The speaker model I used in my simulations was not a broadband model as yours, but rather a very simple single-frequency model. Would it be possible to obtain a copy of the "Amazing Loudspeaker" model you used?

Like many others before me, [I find

that] letters to Stereophile have disappeared into a black hole. In my latest effort, I

pointed out to them that the phase angle in their speaker impedance/phase plots has the polarity reversed! Readers should be aware

that all of the phase plots to date are incorrect. A simple setup parameter on the Audio

Precision would have corrected this.

Thank you again for your interest and

kind words.

[Four weeks later:]

In my last letter, I mentioned the gross

error in the speaker phase plots published

in Stereophile. Well, Stereophile has finally

acknowledged the error in their speaker phase plots, but just barely. It appeared in a footnote in the third speaker review in the November 1991 issue (p. 167). The first

two reviews made no mention of any previous errors, even though the current plots were corrected. In the footnote, Mr. Atkin-

son says that only some of the plots are wrong. I can say without hesitation that all

of the plots performed on the Audio Preci-

sion between May 1990 and October 1991

are incorrect. I can't believe they got it

right once but not now. Only one plot that

didn't use the Audio Precision seemed cor-

rect (B&W Matrix 800, June 1991), but it

is hard to tell since the scale factor on the

graph spanned 180° in inch. Mr. Atkin-

son also says how he's puzzled at how this

could happen. I suggest he read the Audio

Precision owner's manual. Perhaps it's nev-

er too late.

Sincerely, Fred E. Davis Hamden, CT

Coming from an electronics engineer

and author of the excellent paper on loud-

speaker cables in the June 1991 issue of the AES Journal, your favorable comments are

especially welcome. I've received similar encouragement from a good many other

professionals; indeed, it appears to be a

nonnegotiable requirement of hostility to this publication not to have an education in

physics, mathematics, or engineering.

I'm reproducing the circuit of the

Carver "Amazing Loudspeaker" Platinum

Mark TV here in response to your request. I just didn't want readers to get involved in it

and miss the main point of my article.

As for Stereophile's problems with the

Audio Precision gear, it has always been

my impression that they used it for cosmetic purposes—the "scientific" look-and-feel

Schematic of the loudspeaker system circuit used as the load in the computer simulations of speaker cable response in Issue No. 16. The various tuned circuits are for equalization (trimmers shown as singlevalue resistors).

of their pages—rather than as an investigative tool.

—Ed.

The Audio Critic:

I must admit that I really do enjoy your magazine. When I first got into stereo back in about 1979, I used to believe any-

thing the stereo salesman told me. I was

reading a lot of Stereo Review and High Fi-

delity magazines. The high-end stereo store

that was in my town at that time would always tell me that I couldn't believe anything I read from these magazines (to include Audio magazine too!). They convinced me that magazines of this type accepted too much advertising to be impartial in their reviewing.

I would go to this high-end stereo store and wait with bated breath for the words of wisdom to spill forth from the ste-

reo salesman's mouth. The main problem was that I could never really hear the great differences between amplifiers/preampli-

fiers/turntables (of course they only lis-

tened to "belt-driven" and never, never,

never to "direct-drive") that I was supposed

to hear. Of course, the stereo salesman could hear all of these supposed differences

readily and was only too quick to point

these differences out to me.

I don't know exactly when, but at one point I started asking myself why was I listening to this garbage that this supposed "expert" was putting forth. Did my ears not have a vote? Was my opinion not valid? Who made this "expert" the only vote in town?

After some real soul-searching I discovered that I could learn to trust my own

judgment. I started reading about double-

blind listening tests in Stereo Review and started to really wonder about the validity of some of the claims of my high-end stereo store. I also started to wonder about the validity of the high-end magazines. I could not hear the great, huge, unbelievable, etc., etc., differences that were purported to exist. At this point I decided that they probably did not exist (at least in the range of

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human hearing capabilities). This is when I started to get smart.

I was extremely disappointed when

High Fidelity magazine merged with Stereo Review, Another of the only rational stereo

magazines gone and only the disappointing high-end stereo magazines to deal with.

When I first sent my money in to your company, I thought that you would be like so many other high-end stereo magazines that I've tried but just can't stomach (i.e.,

TAS, Stereophile, etc.). What I found in-

stead (and much to my delight) was a ratio-

nal, well thought-out, grounded-in-science magazine that relied on my favorite thing

when in comes to evaluating stereo equip-

ment: double-blind listening tests. This is

where, in my opinion, the rubber meets the

road. If these supposed differences are so great, then surely I or the high-end reviewers could hear them. Ha! Fat chance!

If a reviewer isn't willing to stand up

to this kind of unbiased, scientifically setup test, then in my opinion he's full of shit. (Sorry for the poor language but this is really how I feel.)

Again, thank you so much for being a

good reviewer, as opposed to the Englishmajor reviewer who doesn't really know what the hell he's doing but does know how to use adjectives. I'll take the doubleblind reviewer every time! The other highend magazines and stereo salesmen live off the insecurities of the nonsecure audiophile.

Your magazine is a refreshing breath

of fresh air. Please [extend] my subscription.

Sincerely, Robert L. Thompson Fort Huachuca, AZ

P.S. Please write about yourself in

your magazine in the future (i.e., how you got into audio, what schooling you have, etc.). I think people would be interested.

Your case history is instructive and heartening; unfortunately a lot of your fel-

low audiophiles haven't progressed beyond

your initial phase and keep going back to

that salesman for more of his voodoo.

As for my audio bio, let me just say that my hybrid schooling allows me to trade transfer functions with the engineers as well as adjectives with the English ma-

jors. Those who have read every issue of

The Audio Critic actually have a pretty complete idea of who I am and where I'm coming from.

Your supportive comments are greatly appreciated, and your lapse in polite vocabulary is forgiven.

—Ed

The Audio Critic:

I've just finished digesting your introductory package of Issues No. 11 through No. 15. It would have been a bargain at twice the price.

I would like to express my interpretation of your view of the current amplifier/ preamplifier scene to see if I understand you correctly.

What I think you're saying is this: If the given component is free of egregious engineering and manufacturing errors (given the current state of the art), then in all likelihood it will be audibly indistinguishable from a similar component, regardless of any price difference.

Or, to put it another way, if you were to drive, say, a pair of Vandersteen 2Ci speakers, and you were to use as amplifiers a Krell KSA-150 and a Harman/Kardon Citation 22, at normal listening levels a "typical" listener would be hard-pressed to find any major audible differences between the two. I understand that this would not necessarily apply with a much more difficult load, like an Apogee Scintilla, since the Krell has the ability to drive lowimpedance loads without concern.

What I'm really trying to get at is this: The intelligent audio consumer will look closely at his main input sources, his listening room, his speakers, the types of music he usually listens to, and will be able to come up with a list of components that will satisfy his requirements. Then he would look at his monetary restraints and come up with a budget. After all this he will still be looking at a large group of manufacturers, from Adcom, Aragon, and Carver, to Rotel, Sumo, and Tandberg (to name just a few). But the point is that he will in all probability be just as pleased with the sonic performance of any of these brands, and would logically base his decision on price, availability, warranty, service considerations, etc. (given the caveat that you haven't actually tested any of these components, and that there are no compatibility problems, like an amplifier with a power supply/ output capability insufficient for the load it has to drive).

On the lighter side, I've come up with a quick and easy way to differentiate your publication from the others. Here it is: Wide-eyed audio "enthusiast" writes to three audio magazines. He writes: "I've

just put one of those magic bricks on top of

my amplifier, and the sound has improved

100 percent!" The commercial hi-fi audio mag responds: "Wow! There must be something really wrong with your amp!" The "alternative" audio press would re-

spond: "Wow! Another breakthrough. This one we've got to try!" Whereas the most logical (if not polite) response to such an affirmation would be: "Wow! There must be something wrong with this guy!" Can you guess who's going to pick number 3?

Please renew my subscription. Keep

up the good work!

Sincerely, Joel Ellingsworth Austin, TX

Your exegesis of my electronic Welt-

anschauung is essentially correct, but you

leave out an important criterion on which the choice between soundalikes can be based: ergonomics. Some equipment is

much easier and more pleasant to use than

others; the human engineering is so much better. That would influence me more than,

say, a 3-year versus a 1-year warranty.

I realize that your carefully constructed little joke can't be rewritten without ruining your punch line, but your three responses are somewhat off the mark. The large-circulation hi-fi slicks would politely mutter something to the effect that they haven't had the same experience as the letter writer. The alternative audio press would probably try to one-up the writer by bringing up magnetic magic bricks—or something. And I never say "Wow!" unless

I'm wowed.

—Ed.

The Audio Critic:

I [was] pleased to take you up on your subscription offer... I am a longtime subscriber to Stereophile and had already concluded that I could no longer stomach their antirational stance, although they have brought to my attention many fine products. I think that high-end audio is made to appear ridiculous by its cultists, and I am amazed by the self-delusion that prevails. Subjective reviewing is not in itself objectionable, but in the hands of the cultists it supports a rigid hierarchy of manufacturers

who successfully cater to the obsessions of

reviewers and who in turn are manipulated by the manufacturers. The exodus into the cloud-cuckoo-land of line conditioners, CD tweaks, and exotic cables was the last straw as far as I am concerned. I have been an audio hobbyist since the mid-1960s and, although not an engineer, I am at least scientifically literate. I also am a psychoanalyst and I think I know self-deception and obsessive rationalizing. I agree that this is done unintentionally and out of selfaggrandizement rather than simple greed, but it is a great disservice to those who ex-

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pect some kind of substantive information from audio publications.

Manufacturers and retailers should be aware of the effect that this behavior has on consumers; in my own case I have delayed purchases because of the lack of reliable, credible information. I am reluctant to refer

nonaudiophile friends who want something better than department-store brown goods to audio salons where they will get the party line about directional cables and CD stabilizers. The largest untapped market for home audio is among women, and they are having nothing to do with the bilge that comes from typical high-end dealers. They may or may not know physics, but they know when men are kidding themselves. Even the best dealers think they have to kowtow to the superstitions of the cultists; those who do not are referred to contemptuously as mid-fi appliance hawkers. Great way to promote a love of high-quality re-

produced music: adopt a sneering attitude toward neophytes and nontweak products.

I wish you every success with the reincarnation of The Audio Critic. I am glad to find a publication that only embarrasses me occasionally (with a little bit of bombast to make a point) instead of constantly (with flaky, "politically correct" pronouncements about things that exist only in the reviewers' fantasies). I look forward to retrieving this most enjoyable hobby from the audio Moonies.

Sincerely, Michael L. Pipkin, M.D. Houston, TX

Your comments are totally on target;

I'll take exception to two minor details

only.

1. Women are probably not "the largest untapped market for home audio," although it would seem logical to think so. Only 3% of the subscribers to American Record Guide are women, and the maga-

zine's editorial content is all CD reviews

and no audio. No untapped female CD-

player buyers there. How that jibes with the frequent preponderance of women at con-

certs I don't quite understand myself, but I

wouldn't put my life's savings into a ladies'

audio department franchise.

2. Verbum sat sapienti—a word to the

wise is sufficient, but bombast just barely

gets the attention of the unwise.

-Ed.

The Audio Critic:

Today I received a sample copy of

The Audio Critic. Because I have a back-

ground in physics and biochemistry I lean

towards an objective approach for the evaluation of high-fidelity equipment. However, I have been interested in the subject of good music reproduction since 1952 and I know that many of the qualities of sound reproduction equipment cannot be explained by currently used measurements. I also know that the only way to properly carry out an A to B comparison is to first educate the listeners on how to listen, something I gather you do not do. Never-

theless, I thought that your magazine would be useful and interesting. I was prepared to subscribe, but then I began reading your descriptions of your fellow writers in the field as "...self-indulgent, posturing little people... protecting the belief system of the cult...aren't big enough to admit they were wrong..." and similar scurrilous and derogatory statements scattered all through the

journal. I realized that anyone who would

write that way could not be objective or scientific in his evaluation of anyone or anything.

Unhappily yours, Melvin L. Goldberg, M.D., Ph.D. Altamonte Springs, FL

Since you haven't subscribed, you're unlikely to see my reply, but your letter typifies certain attitudes that I want other readers to recognize for what they are. You're wrong on three counts:

1. Anything that can be heard can also

be measured, but the measurement protocol

must suit the nature of the audible phenom-

enon. It's the routine measurements that

sometimes leave us without an explanation.

2.1 only use educated ears, i.e., highly motivated and experienced audiophiles and music lovers—some of them professional musicians—in my listening tests. Whatever made you "gather" the contrary?

3. Strong opinions about other practitioners—including suspicions of smallmindednes and bad faith—are absolutely unrelated to objectivity or lack thereof in scientific inquiry. Are you aware of the opinions of Dr. Edward Teller (who comes

from the same culture as I, a generation before me) about some of the other figures in

the nuclear community? Is he incapable of correct scientific evaluations? If everyone shared your distaste for outspokenness and confrontation, all productive dialogue in our society would die of terminal blandness.

—Ed

The Audio Critic:

Weren't you stunned by John Atkin-

son's implication (Stereophile, August

1991, "Industry Update"/Australia) that the

Garrott brothers and their wives committed suicide because of the commercial success of the Compact Disc? If only John Atkinson and Harry Pearson would take their analog love affair this seriously!!

The Garrott brothers and their wives had to be sickies, and the real tragedy is that these four lives couldn't be given to four terminally ill children.

Joseph M. Cierniak European Technical Center, APO

When I first heard about this, my reaction was, "Hard core, man. Hard core! " Of course, the causes of suicide are more often than not unfathomable, but Stereophile's

priorities are not. They commemorate the

tragedy of these unfortunate designers of tweaky styli, but I don't remember anything in their pages about the equally tragic decease of the brilliant Deane Jensen, whose microphone and phono transformers were almost certainly the finest in the world,

whose circuit analysis program was a

remarkable pioneering effort, and whose

JE-990 discrete op amp circuit broke new

ground in ultralow-distortion amplification.

—Ed.

The Audio Critic:

...It is obvious that you are doing something right. That is of course that you are demanding that high-end manufacturers

stand on the realities of physics....

On the matter of speaker cables, your argument that there are audible differences but that these differences are nothing but

the results of the interaction of the amplifier, the RLC of the cable, and the speaker is persuasive. It is incumbent on those who believe in the superiority of specific cables, and that this superiority is inherent in the construction of same, to prove it with physical evidence. I should note that Frank

Van Alstine has made essentially the same

argument in his newsletter. I look forward to your remarks on interconnects and hope that you will comment further on the question of long interconnects and short speaker cables or vice versa.

With regard to the question whether all electronics sound the same as long as they meet your test conditions, I am not so convinced. Circuitry certainly must transform the signal in different ways in different preamps, for example. Certainly I could identify my Conrad-Johnson PV5 as compared to the transistor preamp I had been using. Further, how do you explain the celebrated Carver challenge to replicate the sound of any amplifier selected by J. G. Holt if in fact there are no differences be-

pdf 9

tween state-of-the-art amplifiers playing

within their design parameters? I should

add that I certainly agree with you that the differences between electronics are not as different as "golden ears" would like us to

believe....

Sincerely yours, Harold Goldman New York, NY

You obviously have a fair grasp of the basic realities of audio but seem to have an incomplete understanding of what happens within the "circuitry" when an input is processed to become an output. Two pream-

plifiers or two amplifiers having very differ-

ent circuitry can still operate on identical inputs to produce identical outputs. In other words, the circuitry can be different but

the transfer function (output divided by the

input) can still be the same, in which case the outputs will be the same. If your Conrad-Johnson and your previous preamp sound different, it's because their transfer

functions aren't identical, not because one

uses tubes and the other transistors. For example, their output impedances could be

different (in fact, I'm pretty sure they are)

and/or one could have more of a high-

frequency rolloff than the other, and so forth.

Now, the Carver challenge would in-

deed be rather meaningless if it started out

with two amplifiers having the same input

impedance, same output impedance, same

frequency response, and same gain. Those

are the principal parameters that Bob Carver massages to end up with identical transfer functions. In the instance of the J. Gordon Holt challenge, such was certainly not the starting condition, but in some cases it could be, and then Bob would have

very little—or possibly nothing—left to do. To that extent, your skepticism is justified.

—Ed

The Audio Critic:

Please consider the two following sets

of questions raised by Issue No. 16.

1. The Sound of Amplifiers, Part I Three key points in the critique of the

subjectivist school of audio evaluation are:

(a) forgoes all double-blind testing methodology; (b) rejects the oft-repeated findings of double-blind testing; and (c) refuses to play "fair" (pick the Carver controversy of your choice).

In its defense, Stereophile has said

they will set up and publish a "fair" doubleblind test (by their understanding of objectivist methodology). Given the right conditions, they believe their "golden ears" can

and will distinguish among amplifiers.

Now, let's make a big assumption. Assume a reputable and methodologically defensible double-blind test is published in Stereophile or some other journal. The test shows statistical significance (>95% confidence level) and practical significance (say

13 right out of 16 tries).

Questions: If such a test were published, what is the probability that their results would be accepted by the objectivist camp as being a valid test ? (The conclusion being that either some phenomenon not accounted for by current objective measures is audible or that the audible level of some measured distortion is lower than

previous objective tests indicate). More to the point, would the objectivist camp be

any more likely than the subjectivist camp

to acknowledge they might be wrong?

(I have my own "reconciliation" of

the two camps. However, I doubt that you

would enjoy wading through my disserta-

tion just to understand my biased view.)

2. The Sound of Amplifiers, Part II Your basic premise is: All competent-

ly designed amplifiers will sound alike if several reasonable conditions are met. Most of your discussion makes reference to amplifiers which behave (more or less) like a

voltage source.

Questions: Do any of the reasonable

conditions change if you include currentsource amplifiers (i.e., the various outputtransformerless [OTL] tube designs)? If not, how can a fair comparison be made with an OTL which can swing several hundred volts into a high-impedance load (such as an electrostatic) ?

Do OTL designs affect the frequency

response of speakers (particularly electrostatics) in a predictable fashion? If so, does this account in large measure for "subjective" reviewers praising most OTL designs, particularly when used with electrostatics ?

Sincerely, Barry McClune Wilmerding, PA

Re your Part I. The subjectivists of the

high-end audio press obviously have a po-

litical agenda: the $1200 amplifier musn't be allowed to sound as good as the $6000 amplifier, otherwise it's the end of the world. I can't speak for all objectivists, but

I and the ones I know well are willing to

live with any outcome, as long as it's true. As a matter of fact, I'd be happier if the $6000 amplifier invariably sounded better;

it's a terrible downer when it doesn't. So, personally, I'd welcome being scientifically proven wrong in some of these soundalike

controversies; a few of my fellow objectivists would possibly have wounded-ego

problems—who knows? The point to re-

member is that truly conclusive objective tests leave no room for argument, whereas assertions of exquisite subjective perceptions always do.

Re your Part II. A highish output impedance makes an amplifier a less-thanperfect voltage source and puts it a small

step closer to a current source, but to my knowledge there's no such thing out there at this time as a "current-source amplifier" designed to drive a loudspeaker (it would have to be a very special loudspeaker).

What an output impedance of 1.1 ohm can do to the response is illustrated in Figure 8 on page 55 of Issue No. 16. Also, you

musn't confuse the two kinds of OTL tube

amplifiers that have appeared over the

years. One is part of an inseparable ampli-

fier/speaker system, driving a specific elec-

trostatic loudspeaker right off the plates, without an intervening transformer. (Early

Beveridge and Acoustat designs come to

mind.) The other kind—the only kind that can be A/B'd against conventional amps— is a more or less universal amplifier designed to drive all kinds of speakers. The

Futterman OTL amplifier (perpetuated

through the mid-1980s by New York Audio

Laboratories) was the origin of the species

and probably its best example. Inherent de-

sign limitations made it quite unhappy with

loads below 16 ohms; the original Quad

ESL was a very good match to it because of

its relatively high impedance. A modern electrostatic like the Quad ESL-63, however, has an impedance characteristic not very different from any number of other speakers, and there's no advantage to driving it with an OTL.

—Ed.

The Audio Critic:

Six months ago I quit smoking and said that if I remained off cigarettes for six months, I'd replace my 10-year-old stereo system (Onkyo receiver, Advent loudspeakers). So for the last six months I've been intently reading the de rigeur periodicals, e.g. yours, Stereo Review, Audio and

Stereophile.

I had read Stereo Review and Audio (and High Fidelity) intermittently over the years, but now I was down to serious business. The ideas I came in with were:

• most high-quality amplifiers would

be equivalent;

• FM would be limited by the signal

and antenna more than by the tuner;

• CD players would also basically

pdf 10

sound alike.

Even if the above postulates were not precisely true, they were excellent working principles. My main philosophy was that, by a large margin, the speakers had more to do with the sound than any of the components. The listening room and the speakers' placement within it would be the second most important factor. Both of these factors would dwarf the other components' contri-

bution (assuming, of course that they were all of good quality).

Those were my working assumptions. When I started to read Stereophile, I was surprised to find that there was a slant or spin to audio that I was unaware of, that of subjectivism. I didn't dismiss this out of hand. After all, oenophiles use the same kinds of words to describe wines. Also, while one reads Stereophile there can be a tendency to become enraptured.

I then saw an ad for your magazine in another audio journal, and the premise stated in the ad appealed to me. I subscribed. I

liked what I read. I loved the debunking.

Eg.:

• quality amps sound alike when level-

matched;

• certain attributes ascribed to preamps

are actually determined by the recording

process;

• double-blind A/A testing gave differ-

ences 35% of the time.

/ love this. It helps to restore some order to the chaos. It affords me armament to do battle with the salesman. It allows me to put my money where my speakers are.

Now to my area of discomfort. Bob

Carver.

I know of Bob Carver from his Phase Linear days. He had a well-respected reputation then, and I always felt that he was an innovator. So when I began to read your magazine, I was not at all surprised to find his products highlighted. And there is Carver bashing in the audio stores (e.g., his amps have high wattage [sic], etc.). The high-end stores rarely sell his products. (One store here does. I saw the "Amazing Loudspeakers" on two opposite walls facing each other, and when I asked about them the "salesman" said: "They suck.")

Having an extended interview with Bob Carver was fine; reviewing his products is fine; but this last issue is too much: (1) Amazing Loudspeaker review again. (2) Touting the Amazing in the Snell review. (3) Review (I think) for the first time a TV, with a sound system by—who else—Bob

Carver.

I don't philosophically or scientifically

disagree with Bob Carver. I find the science

of your magazine credible up to my level of understanding. But when you praise Carver

to this extent, it lowers your credibility. And your message in an important one in audio and should not be dismissed.

Dr. Michael Feinstein Newark, NJ

Your oenophile analogy is a natural one, but check out this quote from the late Frank Schoonmaker's great Encyclopedia of Wine: "...experts, tasting blind, will rarely vary in their ratings of any given

wine, by more than four or five points out of 100. This is a far higher level of unanimity than music critics or art critics or literary critics ever achieve... " It goes on:

"...although the terms [wine tasters] use often appear bizarre or pretentious or even ridiculous to those unfamiliar with them, they are certainly more precise than the language of music critics (a 'lyric' tone, a

'warm' voice) or that of painting ('vibrant,' 'sincere,' 'well-organized')." Now, just substitute the word "audio" in the right places...

As for Bob Carver, he is so much more talented, inventive, and savvy as an audio designer than the high-end cult's typical icons and totems that I enjoy bringing up his name and his products just to see the

tweako partisans freak out. Their designer

heroes are such crashing mediocrities! Ac-

tually, there are only two Carver designs that make Bob a hero in my eyes: the "why didn't somebody think of it before" bass system of his loudspeaker and the incredibly space-efficient power supply of his am-

plifiers. Those are breakthrough ideas that

keep coming up as yardsticks in almost any discussion of speakers and amplifiers. It

just so happens, however, that there's very

little Carver in this issue.

By the way, another superb designer who isn't politically correct in tweako country is Chris Russell of Bryston. You'll read more about his uncompromising yet highly sensible circuit-design philosophy in upcoming issues. And, again, maybe more repeatedly than some will like.

The Audio Critic:

Gee, Peter, either your hearing or

your system is in need of repair. No sonic differences between CD players and/or amplifiers if they're current models and

evenly matched in sound level?? Come on,

you don't really believe that!!

Of course, I used to believe as you

say you do, but after listening to truly high-

end (no, not Carver) equipment, I became

convinced that differences do exist! In sound-level-matched tests (within your stated parameters), my wife has accurately

picked differences in CD players, amps,

cables, etc., in true blind tests!

Spend more time listening and less time bashing Stereophile and TAS, and you'll be happier (so will your readers).

Bob Gash Lees Summit, MO

Gosh, Bob Gash, if Mrs. Gash can hear these differences that the rest of us

can't, we could sure use her in our listening tests. I've always maintained (see Issue

No. 16, page 33) that if a single person can

provably hear a difference that hundreds or thousands of others can't, then it's still a genuine difference to which audio professionals must pay serious attention.

I don't for a moment believe, however, that you really followed my rules; you'd be more specific if you had done so. I bet

you matched levels by ear, not by meter

within 0.1 dB. No good. I bet you tried each comparison just a few times, not a minimum of 12 and preferably 16 times. No good. I bet you talked to Mrs. Gash while switching back and forth, even if she couldn't see what you were doing. No good.

I'd be very surprised if that wasn't

the way it went. You see, my case history is

just the reverse of yours; I believed in these

audiophile-type differences as recently as five years ago and now I don't. My listen-

ing tests as reported in early issues of The Audio Critic were as casual as I think yours are; I set levels by ear and switched

back and forth a few times; sometimes I made comparisons sequentially rather than side by side. (At least I always did the nec-

essary bench measurements.) One day,

urged by certain fellow practitioners, I

matched the levels by meter within 0.1 dB

and had the scare of my life. The damned

things—I don't remember now whether

they were preamps or CD players—

sounded exactly the same! I realized that

level was the crux of the matter. If you

match levels by ear, you'll end up with a

mismatch of 0.4 or 0.5 dB at best, and of

course you'll hear a small difference,

which can then be interpreted as one of

"air," "depth, " "soundstage, " etc., etc.,

and inflated into a big difference.

As for Stereophile bashing and TAS

bashing, where were you and your sharp pen when they started bashing me, long

before I retaliated? (If aggressively insist-

ing that 2 + 2 = 4 constitutes retaliation.)

-Ed.

pdf 11

In Loudspeakers,

Is a Good Big One Always

Better than a Good Little One?

By Peter Aczel

Editor and Publisher

On the cutting edge of the art, which is what we're investigating here, unexpected things happen. The laws of physics favor the good big one over the good little one, but what about a superb little one?

Once again I must refer new readers of The Audio Critic to earlier issues in which my approach to loudspeaker evaluation was explained at length, particularly Nos. 10, 11,

14, and 16. I can't possibly go over the same ground each time I review a new speaker system, even if the review is then not quite self-contained and self-explanatory.

Fried Q/4

Fried Products Company, 7616 City Line Avenue, Philadelphia, PA 19151. Model Q/4 compact 2-way loudspeaker system, $498.00 the pair. Tested samples on loan from manufacturer.

Irving M. (Bud) Fried is one of the founding fathers of consumer audio in America; I first became aware of him in the late 1950s, when he was importing the original Quad ESL from England, thereby rising to high priest status in the eyes of us purists. Later he became a loudspeaker manufacturer, under various brand names, of which Fried Products gained permanence. Under that name his speakers have been reviewed in these pages off and on since 1978, mostly favorably. My overall impression has always been that Bud Fried is both knowledgeable and realistic (i.e., not tweaky) about loudspeakers—although he is (or at least used to be) somewhat reluctant to accept the fact that a transmissionline enclosure obeys the same laws of physics as a vented or closed box—and I know that he is attuned to the sound of live music.

The Fried Q/4 under consideration here is a sleeper. Who would have thought that a rather chintzy-looking pair of bookshelf-size boxes listing for less than $500 would sound better than 90% of all other speakers, regardless of

price? What a buy! If I accept, as I must, the size-related limitations of the Q/A—lack of window-rattling deep bass,

lack of very high SPL capability, same driver for bass and

midrange—then I honestly can't think of anything I'd want to change in its design at this price except the outside of that severely "entry-level" box, which has no provisions to minimize diffraction. Everything else appears to be optimal.

The 8" plastic-cone woofer and 1" cloth-dome tweeter are American-made (by United Speaker Systems in Florida) to Fried's specifications; the tweeter faceplate has the Fried logo engraved on it. The crossover network, which appears to be third-order (18 dB/oct slope) with the tweeter polarity reversed, was computer-designed by Ken Hecht of USS. The enclosure features what Fried calls a "line tunnel," a kind of shrunken transmission line exhausting into a stuffed-up slot; to me it looks as if it had much the same effect as "aperiodic loading." The cabinet is quite solidly constructed, but the finish is cheap-looking vinyl. You can see that the money went into the innards.

The dome tweeter is very impressive; it goes out flat to 30 kHz with only the slightest shelving starting at 13 or

14 kHz but still staying above the -3 dB line. That profile, in combination with the absence of even the smallest peaks (other than those due to cabinet diffraction), results in smooth-as-silk string tone on classical music and totally nonfatiguing highs on any kind of program material. I think this tweeter is in the same league with the JBL pure-

titanium 1" dome; I wish I could have tested them side by side, but I no longer had the JBLs on the premises. The Fried tweeter is crossed over at 3 kHz.

The 8" woofer is also excellent—it has to be when

crossed over as high as 3 kHz. I could discern no bad behav-

ior in the crossover region. The bass response profile of the system is essentially that of a well-damped closed box, with a 12 dB/oct rolloff. The -3 dB point is at 60 Hz, but the

gradual rolloff allows strong fundamentals well below that

frequency. Indeed, the bass of the Q/4 is quite remarkable

for such a small box, so that many users will feel no need

pdf 12

for a subwoofer. On the other hand, the specification in the literature claiming ±3 dB response down to 37 Hz is absurd. The fundamental resonance of the system, as indicated by

its impedance peak, is around 74 Hz.

A full frequency sweep of the Q/4 shows an ever-soslight elevation of the low-frequency range as compared with the midrange and elicits a few low-level buzzes from the cabinet. The overall response is quite flat, with just a mild rolloff of the highs off axis. Tone bursts reveal no storage to speak of; square pulses are more or less recognizable with "sweet-spot" microphone placement but show a nega-

tive-going preshoot (reverse-polarity tweeter) and a very chewed-up top (to be expected with the given crossover network). I find no serious fault in any of these results.

The sound of the Fried Q/4 is, as I said, outstandingly

good—smooth, transparent, uncolored, and highly defined. The ultimate spatial detail is missing, most probably as a result of diffraction due to the sharp edges and corners of the cabinet (Audio Concepts' cabinet design, for example, is better for imaging); even so, I can't think of any speaker system under $500 the pair that can equal the Q/4, while I can think of any number of $1000 to $2000 speakers that sound a lot less accurate and musically satisfying. You can't go wrong with this "good little one."

Snell Type B

Snell Acoustics, Inc., 143 Essex Street, Haverhill, MA 01832. Type B floor-standing 4-way loudspeaker system, $4200 the pair. Tested samples on loan from manufacturer.

This is a big one, the big one designer Kevin Voecks has been working on and talking about for years. It's over four feet high and as wide as an NFL linebacker. How good is it? Very good indeed, but not as good as some of the wildly enthusiastic early reports may have lead you to believe. In my opinion the Type C/IV, at half the price, is in a number of ways a better design. Now, I don't want anyone to walk away with the impression that The Audio Critic gave the Type B "a bad review," so please read my comments very carefully.

First of all, let's all agree that no unheard-of miracles should be expected from a forward-firing box speaker using conventional dynamic drivers, no matter how wellengineered it is. (All right, the enclosure of the Type B isn't entirely box-like—it's a pentagonal column—and there's the rearward-firing extra tweeter which is the Snell hallmark, but the generic classification still holds.) Not even Kevin Voecks can come up with a totally new and vastly more accurate sound within that format. The B has one more woofer and one more midrange driver than the C/IV but it isn't a startlingly different design and therefore it won't take you into a startlingly different world of listening. That's just common sense.

The driver complement of the Type B consists of two

10" woofers, each in its own sealed cavity (and one of them

not really a woofer but a weird sort of bump-up filler— more about that in a moment); two 5" midrange drivers and a 1" dome tweeter in the so-called D'Appolito arrangement (mid/tweet/mid in a vertical line); plus the rearward-firing 1" dome. The woofers are mass-loaded at the apex (obviously because off-the-shelf units having the desired cone mass were unavailable, not because it's a high-tech feature), and the two of them are actually crossed over to each other at—believe it or not—40 Hz, with 12 dB/oct slopes. Above 40 Hz, the bass is handled by the front-facing woofer; the other woofer is aimed away from the listening area and is rolled off above 40 Hz with a humongous LC combination—but it also rolls off naturally in closed-box fashion below the mid-30s, so it produces only a filler bump! This is supposed to eliminate certain interaction problems at the speaker/room boundary; I have no opinion on that at the present time. The upper-woofer-to-midrange crossover slopes are 24 dB per octave; the D'Appolito cluster uses the prescribed 18 dB per octave slopes; the rear tweeter just has a capacitor in series to roll off frequencies below 5 kHz. All drivers are wired in phase. I'll call it an unconventionally configured conventional dynamic speaker system.

On the basis of nearfield measurements (the Don Keele method that so neatly tracks the anechoic curve), I'd say that the bass enclosure of the Type B is a 36 or 37 Hz box—or, rather, double box. The C/IV has a much lower bass cutoff (-3 dB point), but of course the B can handle more low-frequency power and its rolloff is more gradual. On music with lots of bass, particularly timpani, bass drum, heavily bowed double basses, etc., the B is exceptionally potent, clean, and well-controlled. The bottommost bottom, however, isn't in evidence—it's no Velodyne. For $4200, I want it all, from 20 Hz on up, and I'm not getting it. The Snell specification of ±1.5 dB from 20 Hz to 20 kHz "in anechoic half-space with 1/5 octave averaging on the listening axis" is a computer-massaged conversion from full-space reality and not particularly meaningful at low frequencies.

From the bass frequencies on up I found the Type B to be extremely flat on axis up to 20 kHz and beyond; off axis the response is still very flat up to 15 kHz. Truly excellent. The two midrange drivers come in at 275 Hz, the aluminum-dome tweeter at 2.7 kHz. The latter is identical to that in the C/IV, with the same peak at 25 kHz—inaudible, of course, and therefore of no consequence. This same Vifa unit is also used as the rear tweeter of the B, instead of the cheap-but-good Audax that Snell puts into all other models. The rear-panel control for the front tweeter affects only the level matching to the midrange, not the contour of the treble response. The rear tweeter has only an on/off switch. Overall, I'd say that the performance of the B in the frequency domain is impeccable.

In the time domain, my square-pulse test proved once again that 4-way speakers with steep crossovers can have no coherence whatsoever, but then Snell has never had an interest in coherence, and there's authoritative support in the literature for that point of view. Somewhat more disturbing

pdf 13

was the tone-burst test, which showed quite a bit of spurious energy between the tone-burst envelopes in the midrange and the mid/tweet crossover range. This may have been due to interference patterns instead of storage; sometimes it's hard to tell the difference. Suspecting the midrange drivers,

I then discovered that they have hardly any piston excursion but operate almost entirely in the transmission mode. That requires very good termination (i.e., dissipation of standing waves), and I've never seen it done 100% right. These drivers, also made by Vifa, are being used here for the first time by Snell, apparently because of their very flat response on and off axis. I'm not convinced, however, that they introduce no coloration under certain signal conditions nor that they can handle the most taxing peaks on vocal music.

I find something vaguely "not right" in the sound of the Type B that I'm inclined to attribute to the midrange drivers, especially in view of the less-than-perfect toneburst response. It's a subtle coloration or lack of ease or stuffed-up quality, hard to describe and so slight that many will deny it. Another possible source of it is the cabinet, which responds with a distinct pitch when struck in certain places with a small padded hammer I use for the purpose. It's very difficult to build a totally dead large cabinet without going to extremes in the manner of Avalon Acoustics. The cabinet pitch is also approximately in the range that gives me discomfort.

None of this should be interpreted to mean that the Snell Type B doesn't sound good. Of course it sounds good! It's a big, authoritative, dead-flat, clean, obviously high-end speaker. But the absence of the deepest bass and the slight flaws just mentioned make it less than the "ultimate" conventional speaker system, which is what I expected from Snell. It seems to me that the relatively simple C/IV format is easier to implement than the considerably more complex Type B architecture. It's possible that no one could have done it better, with off-the-shelf drivers and just a normally well-built cabinet, to retail for $2100 per side. My respect for Snell is certainly not diminished.

Win SM-10

Win Research Group, Inc., 7320 Hollister Avenue, Goleta, CA

93117. SM-10 Broadcast Monitor (2-way coaxial loudspeaker system), $6250.00 the pair, including stands. Tested samples on loan

from manufacturer.

Dr. Sao Zaw Win, as faithful readers of The Audio Critic know, is the Cambridge-educated Burmese-American

scientist/technologist who is equally at home in a radiationproof life-support suit cleaning up some unsophisticated

nuclear mess and in an electronics laboratory designing high-end goodies for us audiophiles. (Yes, he prefers the latter.) I'll say one thing about his work: he never gets in-

volved in anything unimportant. You won't catch him put-

ting the finishing touches to the industry's 927th tube preamplifier. His turntable of 1978, his FET phono cartridge

of 1987, although not timely enough for commercial success, were landmark designs; his new loudspeaker is that and more: a classic that promises to be the standard for small monitors for years to come. The SM-10 represents a total concept, one that started with a blank sheet of paper; it isn't a repackaging of old ideas into yet another expensive new toy for the insatiable high-end consumer.

Let me say right up front that, for applications where the deepest bass and the widest possible dynamic range are of less than the highest priority, this is the finest loudspeaker known to me. It's simply a cleaner window than any other for admitting the sound into the room. The price is brutally high, but if one disregards the retailer's $2000 markup)— inevitable under the high-end audio industry's current distribution system—the money is right there in the speaker box, in terms of both hardware and development work.

The SM-10 is a small speaker—191/4" high, 121/4" wide, 10½" deep—that mates to a dedicated metal stand

for seated ear-level elevation. The rectangular box, made of 1¼" thick Medex, has perfectly rounded edges, all 12 of them, and is finished with coat after coat of special Italian black lacquer until it gleams like Napoleon's sarcophagus. I understand that the cost of a pair of finished boxes to the manufacturer is over $800. Sheer insanity, but very beautiful. The geometry and construction of the box are the result of extensive Finite Element Analysis, which is beyond my ken, but I can report that the box is deader than any other I've ever tested, totally unresponsive to my knuckles or my little padded hammer.

The raison d'etre of the Win SM-10 isn't the construction quality, however; it's the extraordinary 2-way coaxial transducer, which is radically different from anything used in any other design. Both woofer and tweeter have completely flat diaphragms, and their deployment is both coaxial and coplanar, in other words like a small circle inside a fat ring in the same plane. The size of the woofer is roughly equivalent to that of a conventional 8" unit; the tweeter would be described as a 1" dome if it were a dome and not flat. The crossover frequency is 3.2 kHz.

The woofer diaphragm is made of thin layers of woven carbon fiber compressed with silica gel; the tweeter diaphragm is made of compressed mica and alumina. Not exactly your everyday cone/dome materials. (Sao Win is a specialist in physical chemistry and the testing of materials, so it's no surprise that he shows some originality in this area.) Finite Element Analysis was also used in the design of the diaphragms and other physical components of the drivers; the magnet and voice coil designs are based on

computer programs (Poisson/Superfish group of codes) developed at the Los Alamos National Laboratory by Ron Holsinger, who was once introduced to me as "Captain Magnet." Indeed, there's no seat-of-the-pants design evident anywhere in this speaker; its R & D credentials as documented in the very detailed technical literature that comes with it read like those of a major government defense project.

pdf 14

I was particularly impressed with the optimization of

the tube-vented enclosure. The size/bass/efficiency trade-off in this system is probably the smartest I've ever seen; it was done with the readily available LEAP software, I'm told. The -3 dB point on the response curve I took was at approx-

imately 44 Hz, maybe even a hair lower; the lowest 0 dB

point was at 50 Hz, and the bass response was dead flat

from there on up. (For those who care about such things, the

box is tuned to 56 Hz, and maximum output from the rearward-directed vent is at 60 Hz. These figures could be off

by a hertz or so.) When I first played the speakers, before

taking any measurements, I suspected a little bit of sophisti-

cated cheating in the bass—a bump of a few dB in just the

right place—because the bottom end didn't appear to be

missing at all, but later I realized that Sao Win is too much

of a purist for that. No, he manages to give you the flat bass

extension of typically much bigger boxes, and still with fair-

ly high efficiency (88 to 89 dB). That's close to the ragged

edge of the laws of physics.

Taking the overall frequency response curve of the Win SM-10 is quite a bit easier than in the case of a speaker system with a woofer here, a midrange there, a tweeter over there—and who knows where they coalesce? You just point the measuring microphone at the bull's-eye of the coaxial assembly, on and off axis, and all you have to worry about is not picking up room reflections—everything else is quite uncritical because the wave launch is symmetrical over the entire frontal hemisphere. Piece of cake. I can therefore confirm with some degree of certainty the claimed response of ±2 dB from 55 Hz to 20 kHz on axis; indeed, it's better than that except for a little blip or wrinkle in the crossover region, which takes up the full ±2 dB tolerance. (More about that in a moment.) Although the specs don't says so, the flat axial response continues out to 30 kHz. Off axis the tweeter response is still very flat, but there's a dip in the crossover region that becomes quite marked as the measuring angle is increased.

It would seem, in light of the above, that the crossover network isn't quite as fanatically optimized as the rest of the speaker. I don't want to make a federal case out of this because the measured response is still so excellent and the audible results superb, but I have a feeling that the next production run (the first, from which my test samples came, is sold out) will sound even a little better because it will incorporate a slightly reworked network. (Yes, retrofits will be available, the network being outside the speaker, attached to the stand.) The basic concept of the crossover is rather similar to the one developed by John Bau for his Spica speakers. The woofer is rolled off with a fourth-order Bessel lowpass filter; the highpass filter for the tweeter is mathematically derived to fit the lowpass section as closely as possible in terms of amplitude matching and the desired constant group delay characteristic. My theory—purely conjectural—is that the wave launch from a ring-shaped radiator such as the SM-10's woofer/midrange driver (as distinct from a circular piston) wasn't part of the mathematical model used in the

optimization. I could be totally off the wall here; what Sao Win told me was that the crossover frequency will most probably be moved down from 3.2 kHz to 2.7 kHz—for which the tweeter has ample bottom-end room—and the response in the crossover region will then be expected to flatten out considerably. It's a minor problem in any case.

My time-domain tests painted a highly satisfactory picture. The woofer and tweeter diaphragms both move forward in response to a positive-going pulse. A square pulse input produces a highly recognizable square pulse output, although with some imperfections; the top of the pulse shows a leading-edge spike followed by lots of wrinkles, indicating that the crossover doesn't quite allow perfect coherence. That could change, as I said, in the next run. The spaces between the pulses are very clean. Tone bursts also indicated that there is indeed some kind of mild crossover glitch but revealed no energy storage in the diaphragms. The high-tech "dead" materials are doing their job.

If you've been waiting for a pornographically explicit description of the sound of the Win SM-10, I'll have to disappoint you. It simply reproduces the music. The reproduc-

tion is so transparent, uncolored, and clean that the sound just is—it isn't like this or like that. "Exquisite" was one comment by a casual listener. I don't know of a speaker at any price that equals the SM-10 in this respect. Deeper bass,

bigger whacks on the Telarc bass drums, more spectacular orchestral climaxes, a more room-filling sound I've heard.

Greater accuracy and greater beauty on beautifully recorded

material I haven't. Not that the SM-10 is a wimp. It gives

you a pretty ballsy sound when driven hard with a big amplifier—not to worry, it can take it—and it presents a sur-

prisingly big soundstage in an equilateral triangle setup. I can't imagine a better speaker for a recording engineer or a record producer to take on the road in his car, or for a well-

heeled audiophile to listen to in a city apartment. Eventually, I'm told, there will be a Win subwoofer; meanwhile the SM-10 is merely the bass champion of minimonitors.

I'm inclined to think that the main reasons for the superb sound of the SM-10 are the perfectly symmetrical, diffractionless wave launch from a virtual point source and

the extreme precision of construction. Remember, even the

Quad ESL-63, which is also based on the point-source concept, has limited horizontal dispersion compared with the vertical. Another difference is that the ESL-63 is bumped up at 50 Hz, whereas the SM-10 isn't. Even so, if you like the Quad, you'll love the Win. They come from the same school of wave-front modeling.

Other comparisons that should be made are with the Wilson WATT, comparably priced at retail but with far inferior hardware inside the gorgeous cabinet, and the KEF and Tannoy coaxial designs, which are also basically pointsource radiators but have the serious disadvantage of firing the tweeter through the "megaphone" formed by a conventional woofer cone—unlike the flat, flush, and colorationproof SM-10 transducer. The Win wins on all counts. It's the good little one that can beat a good big one. •

pdf 15

Subwoofer (late addendum)

Audio Concepts Sub 1

Audio Concepts, Inc., 901 South 4th Street, La Crosse, WI54601.

Sub 1 "Synthesized Bandpass" subwoofer, $749.00 the pair (direct from Audio Concepts, fully assembled, including shipping charg-

es). Full kit, $649.00 the pair (including shipping charges). Tested samples on loan from manufacturer.

This very interesting subwoofer arrived too late for a really thorough evaluation, but it deserves to be included here just to make sure that our readers are aware of it. It fills a genuine need by providing deep, clean bass in small and

medium-sized rooms at a ridiculously low price in a very compact package. That's not something to be sneezed at. The design must be judged on its own terms, however, not in competition with something like the Velodyne ULD-15 (reviewed in the last issue), which costs almost five times as much. In the right environment, a pair of Sub l's in combi-

nation with the Audio Concepts Sapphire II minimonitors will give you superior performance even by high-end standards, and the bill will be only $1538.00 for the four-piece system. (No, a single Sub 1 won't do it; it isn't designed for

L+R matrixed operation.)

The Sub 1 is just a little over two feet high and slight-

ly over a foot in both width and depth. Not at all big for a serious subwoofer. The 12" dual-voice-coil driver faces downward, firing into the floor through a space about two

inches high and open on all sides. Needless to say, no highs emerge that way. I suppose that's what makes the Sub 1 a "Synthesized Bandpass" subwoofer because the built-in crossover network has a fairly conventional second-order

lowpass section. The highpass section is just a capacitance

in series with the main speaker; the crossover frequency

could be said to be anywhere from 80 to 100 Hz, depending

on how you define it when the transition is so gradual. The

box has little stuffed-up holes in the bottom panel around

the woofer to give the system the "aperiodic" bottom-end

characteristic favored by Audio Concepts. It's all pretty simple but it works (in the right environment, I must add

again).

In the June 1991 issue ("Three/91") of Speaker Build- er Gary Galo reviewed the kit version of the then brandnew Sub 1. Although I suspect that Gary Galo's audio philosophy departs significantly from mine, I find nothing to contradict in his very thorough review after having made my own tests, which as I said were somewhat hurried. The nearfield response I obtained is exactly the same as he shows: just a peak at 40 Hz with an immediate rolloff below it and above it. That's with the cone firing into open air, obviously not representative of the woofer's principle of operation. The nearfield response taken at floor level, sticking the microphone into the two-inch airspace below the cone when the Sub 1 is standing correctly, is not shown by Gary

Galo; I found that the curve was very similar but indicating

3 dB higher deep-bass efficiency, the rolloff below 40 Hz

being parallel to that of the open-air curve, 3 dB above the latter. Clearly, then, that's not the way the Sub 1 works, either, although the loading effect of the floor is part of the idea. It appears that the design depends very heavily on the low-frequency boost inherent in the boundaries of the room, and a not very large room at that.

Gary Galo shows an in-room farfield response of ±0.5

dB from 22.5 to 90 Hz, with no satellites connected. To do

this measurement correctly takes more time than I had, but I'm quite willing to believe that the response is as good as

that—in his room. In my room (approximately 22' by 20' by 9'), I had a lot of trouble hearing the bottommost bottom, just about regardless of placement. Finally, using the Bill

Rasnake technique (see Issue No. 13, pp. 43-52), I found

two impractical locations for the two boxes that worked

very nicely—the bass drums, double basses, and organ ped-

als sounded just fine. I say impractical because the Sub 1

units were so deep into the corners that the Sapphire II's I

was testing them with had to be set up much closer together

and much further into the room, creating minor bass-to-

lower-midrange transition problems. A crossover close to 100 Hz isn't really low enough to make the subwoofer positions totally uncritical; with 60 to 70 Hz the separation from the satellites would have made no audible difference. Using that nicely woofing but impractical setup I heard lowermidrange colorations that weren't there with Sapphire II's used full range. (See David Rich's caveats regarding the woofer-to-minimonitor crossover situation in the last issue.) In a smaller room, of course, there would have been less separation regardless of the subwoofer locations.

The bass I heard with this not entirely satisfactory deployment was notably clean and well-controlled, without a trace of hangover, confirming the highly damped (low-Q) response claimed for aperiodic loading, which my measurements also showed. My overall conclusion has to be that such a generally good impression under unfavorable conditions implies outstanding results in smaller rooms, where the room boost is always greater and the probable separation between a well-placed subwoofer and its satellite smaller.

Erratum:

In my review of the Carver "Amazing Loudspeaker" Platinum Mark IV (Issue No. 16, pp. 12-14), the price of the loudspeaker is quoted several times as $2199.00 the pair. That was true when I last looked before writing the review— and only for the less costly oak finish—but by the time the issue was published it was incorrect. Price revisions are a continuing process at Carver Corporation, so even if I had quoted the price correctly in the review it would no longer

be correct by now. Here are the correct prices as of January 1, 1992: in natural oiled oak veneer, $2499.95 the pair; in piano-lacquer black finish, $2899.95 the pair. I much prefer the black lacquer finish—it looks appropriately High End.

As for the new prices when judged against the quality of the

product, they're now merely astonishing instead of being totally unbelievable.

pdf 16

How to Squeeze Low Bass from

Small Boxes: a Survey of

Techniques and Trade-Offs

By Christopher Ambrosini, Ph.D.

This inquiry into the feasibility of generating long wavelengths from low-volume transducers attempts to bring a modicum of structured understanding to a subject that has long suffered from vagueness, pseudoscience, and conflicting claims in the popular audio press.

Editor's Note: Christopher Ambrosini is the nom de plume of a highly accredited audio journalist and techie-of-alltrades, who for reasons that have absolutely nothing to do with The Audio Critic doesn't wish to sign this article with his real name. The Ph.D., however, is real, although his academic background is not in electroacoustics.

* * *

Since much, much balderdash has been written about subwoofers both in manufacturers' literature and in reviewers' assessments, the topic of subwoofers seemed to cry out for clarifying remarks from The Audio Critic, particularly in regard to the practicality of making a subwoofer of relatively small dimensions—let us say less than four cubic feet. What follows is an attempt to explore the basic engi-

neering issues and examine some of the more intelligent design approaches.

But before I delve into the minutiae of subwoofer de-

sign, I'd like to say just a few words about the place of this bastard product category in a high-performance music system.

Seldom stated fact: In adding a subwoofer, one is es-

sentially constructing an entirely new speaker system, and unless the subwoofer has been specifically designed to complement a specific wideband speaker system of limited bass output, the integration of the subwoofer into the audio system will present the consumer with formidable problems. The consumer will be faced with the task of determining the crossover point and configuration, arriving at appropriate wave-launch characteristics for the system and addressing problems of room geometry which may not have been apparent with unaugmented bass. In aggregate, these problems and their solutions are worth at least an article in themselves, and should be recognized by anyone contemplating the purchase or construction of a subwoofer. I haven't space to discuss these problems here, but rest assured, they are

considerable.

But if subs as a subspecies are highly problematical, they are not without utility. A properly designed, properly integrated subwoofer can significantly—and I think audibly—reduce intermodulation distortion in many, perhaps most, wide-range speaker systems and of course can add low bass extension and impact to all but the largest systems. And let us not ignore the fact that subs are immediately impressive—something you can show off to those friends of yours unmoved by "air" or "liquidity."

Unfortunately most subs that really deliver the bottommost notes are rather enormous, and all but a tiny handful of the exceptions are dauntingly inefficient or dynamically limited. And this is precisely the point I wish to address in this article.

Is then an everyman's subwoofer even possible? A sub that goes really deep—say below 25 Hz—yet is small, accurate, dynamic, and efficient ?

Many manufacturers will be quick to assure you that such desiderata are fully obtainable in their products, but as snake oil is the common currency of our industry, we need not take such claims at face value. If there's one thing that should absolutely be hammered into the minds of consumers regarding the subject of bass reproduction, it's this: downsizing the woofer enclosure will either lower the efficiency or raise the bass cutoff frequency—one or the other, no exceptions, no mercy. Compactness, efficiency, and bass response are an "eternal triangle"—each of them profits at the expense of one, or both, of the other two. Let us therefore consider the range of realistic possibilities dispassionately and comprehensively.

Defining the category and the problem.

A subwoofer is nothing more than a loudspeaker of specialized function—one designed to reproduce frequen-

pdf 17

cies no higher than 200 Hz and sometimes as low as 15 Hz. Like any high-fidelity loudspeaker, a subwoofer is intended to maintain fairly level frequency response through its passband.

Now in order for any cone loudspeaker, subwoofer or no, to maintain level frequency response with descending frequency, it must maintain constant acceleration through the passband. An inevitable consequence of maintaining constant acceleration is a quadrupling of driver displacement with each descending octave. Said displacement requirement, while rather enormous on the face of it, is essentially inconsequential at frequencies above 200 Hz. A small cone moving mere fractions of a millimeter in the magnetic gap can easily produce a 100 dB output above 200 Hz, and quadrupling that small displacement an octave down poses

no problem. But adding a further fourfold increase an octave further down is another matter, and multiplying by four again to reach down to 25 Hz obviously involves a very large increase in displacement—from millimeters to the or-

der of a centimeter. And that increase takes all but a very

few drivers to the limits of their excursion and beyond.

Something to keep in mind: a one centimeter peak-to-

peak excursion is very considerable for a woofer. Very few

commercially available drivers will do more than that, and

of those that do, most become highly nonlinear as they approach the limits of their excursion because the voice coil is interacting with fewer lines of magnetic flux than at lower excursions. (The highly specialized, dedicated 12-inch

woofers of the Carver "Amazing Loudspeaker" are among

the rare exceptions, with three centimeters linear travel and five centimeters with some nonlinearity.) Flux density may be linearized over long excursions by the use of long voice coils or design stratagems such as the use of magnetic shorting rings, but optimizing motor design for long excursion tends to be very expensive, and most manufacturers opt for another solution—using bigger cones.

A large-diameter cone will always displace more air

than a small-diameter cone for a given excursion, and thus it will not have to move as far at lower frequencies as its smaller brethren. Opting for big cones in subwoofer applica-

tions means, however, that the designer is faced with larger

enclosure requirements because of the need for a greater

panel surface area to mount the driver and the generally

higher box-volume requirements entailed by the use of

bigger drivers.

In other words, the driver itself poses a major obstacle

in achieving significant size reduction in subwoofers. There just aren't that many small drivers of reasonable cost that

perform satisfactorily at low frequencies, and for realistic subwoofer applications a ten-inch cone diameter represents

a practical minimum; in fact, very few systems using tens can produce any appreciable acoustic power below 30 Hz. Twelves and fifteens are generally much more appropriate, and eighteens are not overkill.

But if the driver itself constitutes one fairly hard limi-

tation in terms of downsizing, the enclosure is apt to impose

far more intractable limitations—in other words, with most enclosure designs, you'll never reach the point where the

box is too small to accommodate the woofer.

The box conundrum.

Now let's examine why enclosures inevitably impose

considerable interior volume demands for subbass reproduc-

tion—though of course not all designs are equal in this re-

gard.

It's a well-known fact that in attempting to use a woofer in free air or on a flat baffle, one experiences falling output in the bass region as a result of the cancellation of the primary output by the rear wave. The cancellation will begin to occur when the half-wavelength being reproduced equals the shortest dimension of the open baffle. While open baffle speakers capable of low bass have been made— the Carver "Amazing Loudspeaker," the Enigma subwoofer, and the Celestion System 6000 come to mind—the approach has its limitations, requiring as it does a very large baffle area and/or active equalization, plus highly specialized, dedicated drivers. Hardly the compact, unobtrusive, everyman's subwoofer which we are contemplating.

If we eliminate the flat baffle approach, then we're forced to use a box. Now all boxes under the sun can be placed in two great kingdoms: the kingdom of boxes where only the primary output of the driver is permitted to reach the listener, and the kingdom of boxes with resonant cavities, which either supplement the primary output from the front of the driver or else constitute the whole output themselves. Within these two categories are many variants, but no enclosure design falls outside of this simple division, and within each kingdom are not one but several design variants characterized by remarkably low volume per a given degree of bass extension. I shall describe a number of these variants, but first I must say something about the acoustical behavior of air in enclosed spaces.

Whatever the enclosure design you choose to consider, it encloses a volume of air having the mechanical properties of mass, stiffness (the inverse of compliance), and acoustical resistance or friction. These mechanical properties may be considered to be analogues of inductance, capacitance, and electrical resistance in a circuit, and like the latter they may be manipulated within an acoustical circuit to create a tuned resonance. In a loudspeaker enclosure designed to load electrodynamic cone drivers, the reactive properties of mass and stiffness are always dominant, and it is fairly obvious that the values of both are dependent on the volume of air in the enclosure. A large volume of air is relatively compliant and lacking in stiffness, while at the same time it has considerable mass. Reduce volume and mass is reduced as well, while at the same time compliance drops.

And therein lies the problem for the subwoofer maker. The air in the enclosure is in series with the acoustical circuit of the driver, and together they form a single tuned acoustical circuit, or, more correctly, a series of circuits because all loudspeaker systems have multiple resonances. A

pdf 18

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