Space...the Final Frontier Page 4

A case history
Generally, the engineering community simply dismisses high-end audiophiles as a lunatic fringe. But the High End, itself, has been unabashedly hostile toward the sonic qualities valued by audio professionals.

John Atkinson's 1992 review of the Westlake BBSM-6F and the Acoustic Energy AE3 loudspeakers (Vol.15 No.1, p.207) is a case in point. The Westlake is a typical professional monitor of moderate size, that I understand to have been designed "by the book." The AE3 is a high-end consumer loudspeaker with all that that implies. JA faulted the BBSM-6F for a balance that "favored the midrange," bass that was "shelved down and lightweight at low levels," and "disappointing" soundstage depth. (He also noted a "striking immediacy" and an "extremely open, detailed" sound, neither of which were apparently judged important enough to redeem the product.) The AE3, on the other hand, was generally well received, partly because of "bass that was full and extended."

In light of those reviews, the accompanying on-axis frequency-response curves were illuminating. Give or take the inevitable bumps and dips, the Westlake's averaged response was a horizontal line, while the AE's had the characteristic clockwise warming tilt of the "musical" loudspeaker. [See Sidebar.---Ed.] While frequency response isn't the only determinant of low-end weight (woofer Q is important, too), it is still a major one, and the audiophile preference for that clockwise tilt has permeated almost every review published by the high-end press.

Horse for courses
Well, so what? The extra warmth makes the sound more realistic, doesn't it? That's the catch: It doesn't necessarily.

Since the tilt is fixed and undefeatable, it also affects the kinds of recordings that don't need it. This is what has given rise to the conventional wisdom that different loudspeakers "favor" different kinds of music. It's true. Speakers that sound suitably rich and full-bodied when reproducing large-scale music do sound fat, sluggish, and turgid when reproducing small-scale stuff like jazz, folk music, solo piano, and chamber music. (Rock, in particular, demands a driving, punchy sound.) Conversely, speakers that sound fittingly lean and articulate with small-scale music invariably sound thin and pinched with the big stuff.

Speaker manufacturers will dispute this, because it's in their interest that you not know about it. The fact remains, however, that the speakers which best reproduce the spectral balance of one kind of music sound worst with the other.

To demonstrate why this is so, repeat the previous stereo/mono comparison, but with some small-scale performing groups. As before, the soundstage will collapse when you switch to mono, but the apparent spectral balance will hardly change at all---far less than when playing large-scale music.

The reason for this should be obvious. Most small-scale music is performed (and recorded) in a small acoustical space that doesn't support the kind of reverberant field a large hall does. The room doesn't sound "rich and warm," so the small-scale sound doesn't need the built-in loudspeaker equalization that so enhances the sound of large-scale music. If it gets it anyway, it sounds lousy.

In other words, what we have here is a situation where loudspeakers can either be optimized for one kind of music at the expense of the other, or compromised for both. And that is what we proudly call the "the State of the Art!"

The surround solution
A surround system composed of unequalized---ie, truly neutral loudspeakers---is the only type that can reproduce all kinds of music with the same musical accuracy. With small-scale music, the surrounds are hardly active at all, so the sound is as lean, crisp, and immediate as it should be. With large-scale music recorded with natural hall ambience, the surrounds spring into action and---voila!---natural warmth. This means that a single system can do justice to all kinds of music, without favoring one over another or compromising the quality of both.

Even small-scale recordings are improved by surround reproduction, albeit to a lesser extent, because the body sounds of all acoustical instruments radiate in all directions, and---unless the performing space was very dead---they generate return reflections from the sides and back of the room. Reproducing these from surround speakers gives the instruments the roundness and solidity of real vibrating objects in space, rather than the cardboard-cutout flatness typical of conventional stereo.

Because truly neutral loudspeakers don't back the sound off, they produce much less soundstage depth in stereo than do laid-back speakers---the immediacy and shallowness that JA noted in his review of the Westlakes. Everything sounds closer, sometimes even appearing to be right at the plane of the loudspeakers. But with added surrounds, the soundstage doesn't stop at the loudspeaker grilles; the surround speakers draw it forward and outward. This closer perspective is actually more faithful to the recording itself, which, in the case of an orchestra, is typically miked from a distance of about 15', rather than from the apparent first-balcony perspective we hear from a laid-back "audiophile" speaker. It also allows very close-miked sources to sound as if they're actually located in front of the loudspeakers, which is necessary to reconcile the timbre of the closely miked sound with its apparent distance.

By reproducing recordings with much greater accuracy, a surround system lays the responsibility for musicality squarely on the recording engineer rather than the loudspeaker designer. Except for the improved low end, many recordings won't sound as spectrally correct as before, because, in fact, many recordings aren't very good (footnote 6). (It's hard to make "good-sounding" recordings when you have no idea what buyers are going to be listening to them on.) What does immediately and dramatically improve is the reproduction of the acoustical space that gives every large performing group its unique sound, and assures our ears that, at last, they are in the concert hall.

Footnote 6: Generally, the earliest and latest stereo recordings are the best. During the '60s, '70s, and '80s, recorded sound was in creative free-fall.