RAISIN LEVELS

Sound Power

There are easier ways to lift a raisin than by floating it on sound waves. There's no reason on earth to do it but there is one in space, where the Intersonics Sound Levitator, shown here, is used to hold materials without touching or possibly contaminating them. Combined with a high-temperature furnace (2,800° F), the device can be used for making metallic glasses and other substances not possible or practical to make under normal gravity. The frequencies used are between 15 and 20 kHz. At 20 kHz, objects up to 0.2 inch across can be levitated; slightly larger objects can be lifted at 15 kHz because of its greater wavelength. The levitating wave is quite intense--more than 160 dB SPL.

(It only takes about 10 dB more to ignite a cigarette by the friction of the moving air molecules.) Even so, the heaviest mass the system has yet levitated on earth is 1 gram however, that was a gram of platinum, nearly twice as dense as lead.

An indirect result of Intersonics' space research is a new speaker design-not a tweeter, as you'd expect from their high-frequency work, but a new subwoofer. The Danley driver, named after engineer Thomas Danley, uses a low-inertia servomotor driving a rotary-to-linear converter, rather than the conventional magnet and voice-coil.

It's made for sound-reinforcement work in concerts but may be available in home versions soon. (Intersonics is at 3453 Commercial Ave., Northbrook, III. 60062.)

Remote Mono

One of the nice things about being an editor of this magazine is being able to attend Luncheons of State.

Yesterday's was with Larry Jaffe and Ken Burnett of Studer Revox. Larry had an interesting experience in New England recently, where a Revox dealer replaced a mono tube-type receiver with a very up-to-date solid state stereo unit. Even though he has two speakers, the thrifty gentleman who bought the new piece of gear has not, however, converted to stereo. He listens to the receiver in mono mode and uses its balance control to switch between the speakers, which are kept in different rooms. "Eh-yuh, Marthie, this here stereo's just a fad. It'll go the way of them wax cylinders." E. P.

TweEQ

With all the current foofaraw over imaging, sound stage, rise-time, slewing, TIM and such, frequency response has become the forgotten parameter. Once we'd achieved the magic range of 20 to 20,000 Hz, and the major response differences among components of a given type were smoothed from mountains into foothills, we turned most of our attention elsewhere.

Yet subtle differences in frequency response do account for many of the audible differences among components and some of the most easily perceived ones, at that. Bob Carver has now demonstrated this for two of the underground audio magazines, making one of his amplifiers sound virtually indistinguishable from another amp of the magazine's choice. Other audio wizards have been able to perform similar feats.

So maybe it's time for a tweaking equalizer, or TweEQ: I envision a 31-band paragraphic--that is, a graphic equalizer with a slightly adjustable bandwidth and center frequency for each band-with a maximum control range of ±2 dB instead of the usual ± 12 dB or so. It would not correct for gross problems in the system or the room's acoustics, nor would it be usable as a super tone control. But it would let you erase much of the sonic difference between the good components you already have and the slightly better ones you wish you could afford.

I suspect that the filters would be mild enough to cause few, if any, audible phase anomalies. Internal filter controls could be used to tweak the TweEQ itself to perfect flatness in its neutral control positions. The controls should be knobs rather than sliders, to allow more precise adjustment, to permit the use of rotary-switched precision resistors instead of ordinary pots, and to distinguish the TweEQ visually from ordinary equalizers.

Would audiophiles buy this product? I suspect so. It would deal with the kind of subtle problems which now predominate in high-end systems. It would allow audiophiles to fiddle with equalization without breaking the Unwritten Law against tone controls. Its effects would be mild enough so that no amount of misadjustment could ruin the sound.

And it would probably cost about a quarter of a mint.

Ads Infinitum

Suspicion of business is becoming ingrained in American thought. So we get occasional letters from readers who assume that, when the issue of Audio containing a product review also contains an ad for that product, then the fix is, somehow, in. In real life, it doesn't work that way.

To begin with, the reviewers don't know anything about what ads will appear, or when. The reviewers don't even know, most of the time, what issues their reviews will run in--we decide that only at the last minute, based on what reviews we have, and when the products originally came to us. Newsworthiness is a factor, too.

We editors don't know what ads will run in a given issue, either. We know about how many ads there will be we must, to know how many pages of editorial material there will be room for. (The more ads to bring in money, the more editorial pages we can afford to run. Subscription money is a small part of the equation.) Very late in the issue, we see a series of page-layout schedules which show what manufacturers are advertising (though not which products will be advertised) and whether those ads are black-and-white, two-color or four-color; and the ad makeup keeps changing, right down to press date.

For the most part, manufacturers themselves don't know what issues their products will be reviewed in.

Neither, by and large, does our ad sales staff. So the simultaneous appearance of an ad and a review is usually coincidence.

In some instances, however, manufacturers do learn when their review will appear, and schedule an ad to go along with it. This does not mean they know how the review will turn out (they don't see the reviewer's findings until the issue comes off the press), but they usually assume it will be favorable. Sometimes they assume this because they know how good their products are, sometimes because they optimistically think they know-but they never actually know what the review will say. (We do check with manufacturers on the specs and the purely descriptive portions of reviews in advance, but that's all.) Our ad sales people try to discourage advertising a product in the same issue where it is reviewed, because it's not smart advertising.

Advertisers gain more from distributing their product impressions over many issues than they do from bunching them all together into one.

But if the advertiser insists, well, it's his money.

(adapted from Audio magazine, May 1986; by IVAN BERGER)

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