This series of articles was initially written (in slightly different form), as a paper presented at the 103rd Audio Engineering Society Convention, New York, September 1997. The preprint, "Loudspeakers: What Measurements Can Tell Us—And What They Can't Tell Us!," AES Preprint 4608, is available from the AES, 60 East 42nd Street, Room 2520, New York, NY 10165-0075. The AES internet site, offers a secure transaction page for credit-card orders.
Because I'm suspicious of just twiddling knobs to make the sound "nice," I didn't rely solely on my ears when I used the Z-Systems rdp-1 that I review elsewhere in this issue for speaker and room contouring. Instead, I used the ETF speaker/room-analysis software from Acoustisoft to help me manipulate the equalizer properly. This program can measure the first-arrival, on-axis speaker response, as well as the room response with its early and late reflections and its resonances.
Over the years as a reviewer, I have tracked the swings of opinion and popularity of various audio ideas and technologies. Amid a sea of advanced designs that achieve powerful technical performance and laudable specifications, I'm reminded of a major blind listening test of 18 power amplifiers that I set up for the long-since-defunct UK magazine Hi-Fi for Pleasure back in 1975. We had "advanced technology" then: the transistor amplifier had matured and was well accepted by audiophiles. Prices of the review samples ranged from $300 to $3000 (equivalent to $1000-$10,000 in today's dollars). The auditioning sessions were graced by the presence of many industry leaders, among them the late Spencer Hughes of Spendor, Julian Vereker of Naim, Philip Swift then of Audiolab, Alan Harris then of retailer Audio T., Bob Stuart of Meridian, and John Wright of IMF (now TDL in the UK).
What is the angular separation of your loudspeakers as viewed from your favorite chair? Whatever your answer, it's wrong. Of course I don't mean that it's a factually incorrect answer, just that any single value of subtended angle cannot be ideal for all recordings.
A thorough exploration in a magazine article of such a pervasive and complex topic as vibration control in audio systems is next to impossible; vibration and sound are so intimately bonded that it would be very easy to extend this discussion to just about any area of interest in audio. My intention here is simply to lay a foundation for understanding the basic mechanical forces affecting our quest for improved sonic fidelity, and in the process provide the tools for anyone to achieve good, practical vibration control in his or her system.
As mentioned by two readers in this month's "Letters," amplifiers are used to drive loudspeakers but are almost exclusively measured into resistive loads. The reasons for this are twofold: 1) real loudspeakers both produce neighbor-annoying sound levels and tend to break when driven with typical amplifier test signals; and 2) the question as to which "standard" loudspeaker should be used is impossible to answer---at least the conventional resistive loads are consistent and repeatable.
One of the great imponderables in hi-fi is how much the vibrations of a dynamic loudspeaker's cabinet walls contribute to its overall sound quality. Studies by William Stevens in the mid-1970s showed that, with some speakers, the acoustic output of the enclosure could be almost as much as that from the drive-units. Since then, responsible speaker designers have worked hard either to damp cabinet vibrations or to shift them to higher frequencies where their effect on the music will be less deleterious.
If you read Stereophile regularly, you already know that all audio equipment does not sound the same. But did you know that a given piece of gear can sound better or worse depending upon how it's set up and used? With a few simple tweaks, you can bring out the best in your audio system.
Although I still haven't been able to listen to the Cary Audio Design 805 single-ended tube monoblocks that Stereophile praised so highly a year ago (Vol.17 No.1, p.104), I've recently auditioned many other tubed single-ended designs. Undeniably, a good SE design has a distinctive quality of harmony and atmosphere in the midrange that reaches well beyond the average attainment of its solid-state brethren.
Time to 'fess up: How many of you actually read the "Measurements" sections of Stereophile's equipment reports and understand what's being measured, and why? I suspect that many readers skip over the technical assessment of the reviewed product and make a dash for the "Conclusion."
The Complete Guide to High-End Audio by Robert Harley 450+xxiv pp., $29.95 softcover, $39.95 signed hardcover. Published by Acapella Publishing, P.O. Box 80805, Albuquerque, NM 87198-0805. Credit-card orders: (800) 848-5099.
In the October 1994 Stereophile (Vol.17 No.10, p.39), I discussed my experiences with the DTS audio data-reduction code/decode switch box, which, briefly, is a two-channel box that makes use of the algorithm DTS has proposed for their version of discrete multichannel sound for laserdiscs.
Back in the spring of 1990, Stereophile introduced its first Test CD, featuring a mixture of test signals and musical tracks recorded by the magazine's editors and writers. Even as we were working on that first disc, however, we had plans to produce a second disc which would expand on the usefulness of the first and feature a more varied selection of music. The result was our Test CD 2, released in May 1992.
Anyone who's ever looked for it knows how rare audio-friendly living space is. Perhaps someday an enterprising developer will build Audiophile Acres---a whole subdivision of audio houses or soundproofed condos that'll meet these needs---then stand by while hordes of long-suffering audiophiles stampede the sales office, frantically waving down-payments in their sweaty hands.