Someday we may speak wistfully to our grandchildren about the "golden age" of digital audio when consumer formats (CD and DAT) contained a bitstream that was an exact bit-for-bit duplicate of the original studio master recording—not a digitally compressed, filtered, copy-resistant version whose sound is "close enough" to the original. Digitally compressed formats such as DCC and MiniDisc represent, in effect, a return to the pre-CD era when consumer-release formats were always understood to be imperfect copies of the studio original. Even the most ardent audiophile accepted the fact that LPs and mass-produced tapes did not, and could not, sound as good as the master tapes they were derived from.
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.
At the February 1991 Audio Engineering Society Convention in Paris, Audio Precision's Dr. Richard Cabot (see my interview in January 1991, Vol.14 No.1) proposed a new technique for measuring noise modulation in D/A converters (footnote 1). The method, based on psychoacoustic principles, attempts to predict the audible performance of D/A converters. Now that Stereophile has added digital-domain signal generation and analysis to our Audio Precision System One, we can employ Dr. Cabot's technique and see if there are any correlations with subjective performance.
Editor's Note: This article is now only available as an Audio Engineering Society preprint, under the title "The Role of Critical Listening in Evaluating Audio Equipment Quality," preprint number 3176. The price is $4.00 for AES members, and $5.00 for non-members; it can be ordered (currently on paper only, not as a downloadable pdf) by entering the number in the appropriate field on the preprint search page at the AES website.
Bass constitutes one of the least understood aspects of sound reproduction. Opinions vary greatly on matters of bass quality, quantity, and perceived frequency range or response. Moreover, the bass region is subject to the most unwanted variation in practical situations due to the great influence listening-room acoustics have on loudspeaker performance. Every room has its different bass characteristic, and changes in the position of speakers or listener also constitute major variables at low frequencies.
High Fidelity Audio/Video Systems: A Critical Guide for Owners by Howard Ferstler 253 pages, $23.50 softcover. Published by McFarland & Company, Inc., Box 611, Jefferson, NC 28640. Tel: (919) 246-4460.
Room acoustics, and their importance, may not be subjects which we ponder daily here at Stereophile, but they are never far from our consciousness. Two recent events served to spotlight them yet again: the setting-up of our first-ever panel listening test of moderately priced loudspeakers (Vol.14 No.7), and a letter from a reader requesting advice on room problems. Both reminded us---if a reminder was needed---that although the perfect room does not exist, there are things that can be done to make the most of even an admittedly difficult situation. That reader's letter, in particular, brought home the fact that we cannot really discuss this subject too often. It's easy to forget that comments made here months (or years) ago are beyond the experience of newer readers. A new audiophile's most frequent mistake is to overlook the significance of his or her listening room, while the experienced listener will too often take the room for granted.
In the real world, "knowledge is power" means that if I know more about something than you do, I am better able than you to control it or use it to my own advantage. This is no less true in high-end audio, where a gut-level understanding of how a component works can free its owner from the constraints and frequent inaccuracies of instruction manuals, folklore, advertisements, and the nugatory, nullifidian nonsense in the mainstream audio press assuring you that most of what you know damn well you are hearing is really only a figment of your imagination.
Jitter is not what digital sound quality induces in the listener; rather it is the instability in the clock signal that controls exactly when the analog waveform is sampled in the original A/D conversion, or when the digital word input into a DAC results in an analog voltage being produced at the chip's output. "So what?" is the response of digital advocates, "As long as a digital one is recognized as a one and a digital zero as a zero, then how can there be any difference in sound?" goes their argument, normally culminating in a fervently expressed "Bits is bits!"
Tweaks have acquired a bad reputation in certain sectors of the audio world, probably with some justification. Warming the cartridge to exactly the right temperature, suspending cables from the ceiling (but not with cotton string; it sounds grainy and dry), stroking CD cases with a "magic" brush, drinking "polarized" (or is it de-polarized?) water before a listening session---gimme a break!
While the LP-vs-CD debate continues unabated among high-end audiophiles, the rest of the world has already closed the book on the venerable LP. All but a few specialized classical record companies (footnote 1)(and some weird magazines) have ceased releasing new LPs, few record stores sell them any more, and consumers who wouldn't be caught dead owning something that wasn't trendy have long ago dumped their LP collections for cents on the pound.
"The large peak at 16kHz reported by Stereophile...was nowhere in evidence...The most probable explanation of this discrepancy is that the [Waveform supertweeter's] very light ribbon depends on the air load for damping, and that load is much smaller in the thin air up there at 7000' in Santa Fe than at altitudes where less lightheaded and scientifically more accountable reviewers dwell." Thus spake Peter Aczel (footnote 1), erstwhile loudspeaker designer and Editor/Publisher of the reincarnated The Audio Critic, a publication that advertises itself as having "unusual credibility among the top professionals in audio."
The promise of "perfect sound forever," successfully foisted on an unwitting public by the Compact Disc's promoters, at first seemed to put an end to the audiophile's inexorable need to tweak a playback system's front end at the point of information retrieval. Several factors contributed to the demise of tweaking during the period when CD players began replacing turntables as the primary front-end signal source. First, the binary nature (ones and zeros) of digital audio would apparently preclude variations in playback sound quality due to imperfections in the recording medium. Second, if CD's sound was indeed "perfect," how could digital tweaking improve on perfection? Finally, CD players and discs presented an enigma to audiophiles accustomed to the more easily understood concept of a stylus wiggling in a phonograph groove. These conditions created a climate in which it was assumed that nothing in the optical and mechanical systems of a CD player could affect digital playback's musicality.
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