Letters (Feb. 1997)

Redressing Greenberg

Dear Editor:

Something's amiss when of Aunt Corey Greenberg becomes the gatekeeper for "good" rock 'n' roll ("Front Row," October 1996), telling us to disdain "boring" mass produced rocklite in favor of the canonical standards he unlocked in the vaults of Nor ton Records.

Sure, there's quite a bit of junk out there.

But for Greenberg to set up a hierarchy of taste for music that is, by definition, anarchic and classless is an off-target move to lower Aesthetica. Good rock 'n' roll appeals to prurient interests and relies on reproductive rhythms as much as artistic ones. In other words, rock's vulgar! We love you, Corey, but we're talkin' mongrel rather than Russian wolfhound here. Let the "old farts" (remember them?) deal with taxonomies of taste-instead, put on Joe Ely, The SubDudes, or Joan Osborne's live ver Hand Man" and remember that good rock 'n' roll is everywhere, not just consigned to esoteric dust bins.

Greg Comnes Tampa, Fla.

Horns? You're Darn Tootin'

Dear Editor:

In his October 1996 "Mondo Audio," Ken Kessler takes a stab at horn-loaded loudspeakers. He remarks that owners of tube equipment, of single-ended amps in particular, are the only ones who have any use for horns. The implication is that the high efficiency of horns is, in and of itself, the only useful thing about them and that they are not inherently a hi-fi product.

No doubt about it, if you only have a 12-watt amp, a sensitivity of 102 dB is a dandy thing to have. However, if you drive a well-designed set of horns with a modern mid- to high-powered amplifier, you will discover other qualities Kessler doesn't tell us about, such as startling transients, bowling-ball bass, and vocalists breathing down your neck.

I'm not making this up. The idea behind horns is simple but effective. By mechanically amplifying the sounds coming from the cone, you needn't drive it nearly as hard. You also couple the air in the room to the air in front of the cone more effectively.

It makes for presence you wouldn't believe.

I didn't begin building horns until many years after my love/hate affair with tube amplifiers was over. And I'm not running low power. The amp I use is a 325-watt/ channel MOS-FET. It's hooked up to a set of folded three-way corner jobs the size of washing machines.

It's a good thing I live in a cinder-block structure. I've dimmed house lights and shifted the gears of cooling fans with this "1930s cinema rig," as Kessler puts it. The horns have not disappointed.

Horns are no longer in fashion, because they are big. Period. And that's a shame, be cause today's program material sounds so good on them. I have never understood why, as the signal gets cleaner and its dynamic range becomes wider, speakers be and more anemic. Don't even get me started on home theater; real theaters use horns.

Nowadays, people spend hundreds of dollars on cable in the name of recovering all the signal, only to send it to shoebox-size speakers. Then they use a subwoofer, which is tantamount to slapping a patch on a hole.

I've heard these systems. The bass certainly goes down low, but it is rubbery and fake disembodied. And half the time, none of the levels are matched right. No wonder these systems are in a continual state of "upgrade"! You really want to upgrade? Go get a set of horns.

-Matthew Holup Spencer, Mass.

Repair and Cherish

Dear Editor:

I enjoyed Ken Kessler's "Mondo Audio" column in the November 1996 issue, in which he asks people to bury their old equipment and marry the new. Granted, there is some fantastic new stuff on the market, and sometimes I buy it. But I also relish the old equipment from the '60s, '70s, and '80s. (I guess my age is showing; I re member 78s.) For me, the progress of re produced sound is a miracle of our age, and what has preceded us should not just be buried but cherished.

While it is true that some people may have unrealistic expectations about repairing equipment, I am amazed how few re pairs most things need and how minor most repairs are. A lot of old equipment is still working as well as the day it was made. Talk about value!

-Richard Bourain Santa Barbara, Cal.

Frothing Over Foam

Dear Editor:

Your October 1996 "Audioclinic" had a question about replacing rotted speaker foam. I recently had to do this for the second time and am very pleased with the outcome.

I have an old pair of Dahlquist DQ10 speakers and had to replace the foam surround in one woofer about five years ago. I sent it back to Dahlquist; the job took several weeks, and it cost about what a new woofer would cost.

A few weeks ago, I found that the other woofer had developed the same problem.

This time I contacted one of your advertisers, New Foam. They were very helpful on the phone. I sent the woofer out on a Tues day, and it was back, fully repaired, the following week! New Foam's price was half of what I had paid previously. I recommend the company highly.

-David Adler Clark, N.J.

AdMIT It

Dear Editor:

Music Interface Technologies would like to respond to Dennis Colin's letter (December 1996) regarding our ad. We agree with Mr. Colin in his analysis of passive audio product advertising. With research facilities containing over $500,000 worth of sophisticated test and measurement equipment from such companies as Hewlett Packard, Fluke, and Tektronix, MIT prides itself on being a measurement-based technology leader in high-end audio. In fact, MIT supplies some leading high-end speaker companies with support for their passive component engineering needs in areas such as crossover design. As a company founded on scientific methods and engineering skill,

MIT also takes offense at many audio cable advertisements that make preposterous claims. Such ads cast an unfortunate shadow over the entire industry.

Mr. Colin's criticism is based on our differing definitions of efficiency. Some back ground on the technology and terminology represented in our graphs might be helpful.

Two criteria are depicted in the graphs: Final Energy Component and Efficiency.

These criteria follow from our fundamental discovery that musical energy is momentarily stored in the cable during its flow be tween audio components.

In its electrical form, a musical signal comprises voltage and current. Capacitors store energy in the form of voltage in their electrical fields, and inductors store energy in the form of current in their magnetic fields. These storage phenomena occur in cables because of the inductances and capacitances intrinsic to all cables.

Because of these storage phenomena, MIT views (we believe correctly) an audio cable as an electrical energy-storage device, and we refer to the total amount of energy stored in the cable as the Final Energy Component. The formulas relating inductance and current-and voltage and capacitance-to the amount of energy stored in each (given in joules) can be found in any basic electrical engineering or physics text.

The result is that a speaker, for example, receives two sources of musical energy during operation: that from the amplifier, which is directly coupled to the speaker, and that of the smaller amount of energy that is briefly stored in the magnetic and electrostatic fields of the cable and then supplied to the load.

When one works out the numbers, the amount of energy stored in a typical audio cable is on the order of microjoules. While this appears to be a small amount of energy, we have found that it has audible significance out of all proportion to its measured magnitude. Please note that, though in the graph of Final Energy Component the energy value of ordinary 12-gauge zip cord has been normalized to a maximum of 1 joule to better facilitate comparison, the relative values and curve shapes are correctly scaled for all compared cables.

Our ability to measure and quantify the energy storage and transfer characteristics of cables is a major breakthrough in high end audio, because we have found that this is audibly significant in two ways. First, audio cables store energy in a nonlinear manner with respect to frequency. This is indicated by the top graph in our ad, Final Energy Component. Second, energy that is stored in audio cables is not always efficiently transported to the load, as indicated in the second graph in our ad, labeled Efficiency. Efficiency, like the Final Energy Component, is also not linear with respect to frequency.

Efficiency is measured and scaled in a be wildering variety of ways from one scientific or engineering field to another. In our graphs, efficiency relates to how much of the Final Energy Component is ultimately transported to the load as in-phase power. This means that some of the energy stored in a cable as voltage and current is released to the load with voltage and current out of correct (that is to say, original) phase. This condition results in the out-of-phase energy manifesting itself as noise. The graph of this behavior, apparently the source of Mr. Colin's criticism, indicates that Efficiency is found to be especially poor in ordinary audio cables at low frequencies, such as at 60 Hz.

To correct for these anomalies, MIT developed and patented Output Terminator technology. Our Output Terminators are passive networks placed near the ends of our audio cables. They serve to increase and linearize the Final Energy Component and to ensure efficient energy transportation to the load with less noise. The result is better bass, clearer midrange, smoother highs, and superior image focus and soundstaging when compared to "just cable." It is important to recognize that the MIT Efficiency graph applies only to the energy that is stored in the cable and then released to the load. The Efficiency graph does not apply to the energy that is directly coupled to the load.

The efficiency improvement to which Mr. Colin seems to refer in his comment about rewiring his house is related to the directly coupled energy transfer. Mr. Colin can improve this efficiency through power-factor correction, a technique used in industrial applications and actually required by a power company in severe cases of low power factor. We can help Mr. Colin achieve an improvement in this area of energy transfer. Our patented Z-Circuitry, found in some of our Z-Series AC power-line conditioning products, provides power-factor correction while reducing noise on the AC line, an effect lauded by many critical listeners as being crucial to overall audio system performance.

MIT's Z-Circuitry and Output Terminator technologies are distinguished by the fact that the Z-Circuitry operates on the full AC potential, while the Output Terminator technology described in our ad operates only on the energy that is stored in, and then transported out of, the cable itself.

To illustrate this point using Mr. Colin's example, if he were to wire his home with MIT Terminator Interfaces, the graphs would apply only to the 60-Hz energy that is stored within the wiring. Because of the relatively small amounts of energy involved, as mentioned above, this would have a measurable but (unfortunately) negligible effect on his power bill.

We believe our definition of Efficiency is legitimate, however narrowly circum scribed, and we also believe that Efficiency is the best way to describe the phenomenon we have identified.

We apologize for any confusion resulting from our ad not containing a definition of Efficiency as we use the term, and we will attempt to clarify this in future ads. However, we stand by the scientific results presented in our ad.

Under our 30-day, no-risk purchase plan, anyone can experience the overall sound quality improvement that our Output Terminator technology makes. We invite Mr.

Colin, and other music lovers, to try our MITerminator Interfaces under this risk free plan. We are confident that most listeners will agree that the sonic benefits of our technology are genuine and that MIT's definition of Efficiency is valid.

-Bruce A. Brisson, Director of Research and Development

Timothy A. Brisson, Director of Engineering

Music Interface Technologies Auburn, Cal.

Dozen Doesn't Do It

Dear Editor:

In the November 1996 "Spectrum," Ivan Berger discusses the inside-out coaxial speaker used in Eastern Acoustic Works' Model CP621 Phase Aligned Array speaker.

In describing the design, Berger states that the six 5 1/4-inch woofers around the rim of the tweeter horn's flare combine "to pro vide the effective radiating diameter of a 21-inch woofer." This diameter seems awfully large. Could Berger mean a 12-inch woofer?

-Tom Ace, San Francisco, Cal.

Author's Reply:

No, I don't mean 12-inch. The area of the individual drivers does, indeed, add up to about 130 square inches, not that much larger than the 113 square inches of a 12-inch cone, or equivalent to about a 13-inch cone. But at bass frequencies, these drivers couple together to act like a driver the size of the total array. If the unit as a whole is 24 inches across, and each cone is about 11 inches in from the edge, then the circle of cones does have a diameter of just about 21 inches. At higher frequencies, the drivers no longer couple but instead act as individual 5 1/4-inch midranges.

-I.B.

Direct Stream Critical

Dear Editor:

I have two questions about John Eargle's "Currents" (October 1996), in which he discusses Sony's Direct Stream Digital (DSD) recording process.

First and foremost: Have people's ears changed? The last time I checked, most people's hearing stopped at roughly 16 kHz, so who gives a damn about response to 100 kHz? Second, Eargle mentions a Schoeps microphone (a brand I've never heard of, de spite 30 years as a stage musician) but does not mention the brands of the other equipment in the chain. Is there a reason why we're being kept in the dark about them?

-Edward George French Dallas, Tex.

Editor's Reply:

Although it is true that most people cannot hear much beyond 16 kHz, an ideal sound system would have flat response up to the limits of the most acute listener's hearing, which would actually be somewhere slightly above 20 kHz. And while DSD's 100 kHz goes well beyond that, the system's bit capacity can be reallocated to get lower noise in the audio band, or more audio channels, instead of 100-kHz response. In practice, some of the extra response is bound to be traded off for quietness or extra channels most of the time.

Schoeps condenser microphones are more commonly used for recording than for stage performances, unless those performances are being recorded live. Eargle says that the mike preamps were made by Avalon, an Australian manufacturer. The signals from the preamps were fed directly to the recording system.

-LB.

Blind Ambition

Dear Editor:

After reading Peter Aczel's letter in the November 1996 issue, I have a few thoughts on the subject of A/B/X testing, arising from this question: If A/B/X testing is, as many listeners feel, inherently flawed, there should be a reason. But what would it be? I have personally experienced the diminishment of audible differences that matching output levels introduces into sighted A/B comparisons and the further elimination of differences introduced by making the same test blind. It's quite an education for an open-minded audiophile to do matched-level blind comparisons for the first time. After reading and thinking about both sides of the debate for years, it occurred to me where the flaw in such comparisons may lie. It certainly doesn't lie in matching levels or any other of the methodologies mentioned by Mr. Aczel, save one: blind listening conditions.

The need to eliminate the "placebo effect" in critical listening is clear, but I have begun to question whether it can be done without diminishing perceptive ability.

Consider that the placebo effect refers in medical research to the effect unconscious processes have on the body: that is, psycho logical cause, mechanistic effect. For such investigations, double-blind test protocol proves invaluable. But in listening tests, blind conditions have been used to eliminate delusional thoughts arising from the unconscious. This is accomplished by disallowing assimilation to the conscious (and hence, unconscious) of which component is being listened to. The question is: Can we do this without deleterious effect? Isn't perception a process as likely enhanced as it is damaged by the conscious/unconscious link? Isn't it self-evident that when any perceptual activity is at its most acute, unconscious processes invariably play an integral and enhancing role? Have we, in a well-intentioned attempt to eliminate the delusional component in critical listening, thrown the baby out with the bath water? In simplest terms, perhaps hearing acuity is improved when we know what we're listening to. Critical perception of audible cues seems improved, possibly because of memory enhancement in long-term comparisons.

(Diminishment to the effect of memory may explain why some listeners characterize blind tests as stressful and confusing.) If this is eventually shown to be true, we move backwards somewhat in our belief in rigorously established quality differences with blind comparison tests, since we then appreciate that there may be no precise way to differentiate negative and positive unconscious effects on perception. Even so, we wouldn't be back to square one; we know that A/B/X comparisons give more information than they mask. The magnitude of audible differences falling below the A/B/X detection threshold is comparatively small. But even these magnitudes might explain how the differences listeners nearly universally report disappear under blind conditions. The relative importance assigned to those differences in aesthetic terms would be back in the subjective realm and, of course, worthy of investigation and debate.

We should begin to question the assumption that blind comparison testing is predicated upon: that the inadequately termed "placebo effect" can have only negative impact on the activity of critical listening. Perhaps a few parallels might illustrate the general type and magnitude of the phenomena in question: fuzzy intelligence in recent powerful digital programs or, in audio, dither improving the audibility of very low-level signals in digital processing. Subtle, perhaps, but possibly important.

Dave King, New York, N.Y.

Editor's Reply.

This is an issue we hope to explore in depth in the future. Briefly, for now: I know of no evidence that properly conducted blind listening tests obscure genuine sonic differences. Quite the contrary, in fact. Controlled comparisons of long-term, open listening versus blind listening suggest that the latter is actually a more sensitive (as well as more reliable) discriminator of such differences.

-M.R.

(adapted from Audio magazine, Feb. 1997)

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