It didn't sound too promising. "Why don't you fly out to New York and get the lowdown on this guy's 'home concert hall,' "said AVI editor Maureen Jenson. "It sounds interesting."

I suspected it was punishment for missing my most recent deadline. I'd been a high-end audio retailer, and I'd heard it all before. I was flying across three time zones to listen to yet another audio tweaker describe his method of "unlocking the secret to concert hall realism"-and other heretofore unknown mysteries of the universe.

From my seat, 30,000 feet in the sky, I could picture this guy's setup. He's probably dangling a dozen precisely-cut lengths of five-pound fishing line from thumb tacks above each speaker and amplifier, I thought to myself. Or maybe he's arranged all his components and speakers in such a way that the electrons always travel downhill, unfettered by gravity.

Every audiophile with a pet theory seem compelled to hatch a name for it, and Ralph Glasgal-who was waiting for me at LaGuardia airport that Tuesday evening-is no exception. He's dubbed his theory "Ambiophonics."

Glasgal's mission, as he enthusiastically explained to me on the way to his home in New Jersey, is to venture "beyond today's surround sound to the achievement of concert-hall soundfields in the home, using standard, available recordings."

It turns out, Glasgal is not a "tweaker," and Ambiophonics has no connections to fishing line, gravity, yarns or other bizarre theories. After demo'ing chamber music, symphonies, opera, jazz, pop and even show tunes, there was no getting around it: This ambio thing worked like nothing else I'd heard before. There was a distinct sense, not of having the musicians in the listening room (which the best conventional systems can manage) but of something quite different-of me being in the concert venue. It was a more palpable, you-are-there (as opposed to they -are-here) effect than any demo I'd ever heard. Ambiophonics offered razor sharp imaging-a jaw-dropping knack for painting a believable, three-dimensional picture of musicians playing in a real hall.

By fiddling with a few knobs, Glasgal could change the apparent size and acoustical personality of the concert venue. It wasn't just impressive, it was real-a verdict shared by some 70 other hardened, show-me audiophiles during a public presentation the next evening.

All About Crosstalk

Glasgal's layout doesn't look mainstream. Yet most of Ambiophonic's theoretical underpinnings are well established among researchers and practitioners in room acoustics, psycho-acoustics and digital signal processing. The Glasgal Domestic Concert Hall as Stereophile magazine termed his 800-square-foot, three-story high listening room, contains commercially available speakers, processors, amplifiers, speakers and acoustical treatment. It's the logic behind their deployment that makes Ambiophonics work.

Before launching into the whys and wherefores of Ambiophonics, it's useful to review why traditional stereo systems can't manage much more than a crude suggestion of the spatial signature of real concert venues. The first problem is already understood by seasoned readers of this column: When the ear/brain system receives conflicting cues-say one set from the playback system that purrs, "You're in a fine old concert hall!" and another set from the playback environment that that bellows, "Nope you're in a suburban family room!"-it tends not to wholly believe either. Thus, the Ambiophonic technique begins by removing most to the room's sonic personality. This typically entails the installation of broadband absorbers throughout the space, with the goal of reducing reverberation time to about 200 milliseconds. Thankfully, absorbers can be ordered or cut to fit, and are typically the cheapest of all room treatments.

The second problem in traditional playback systems is that sound from the left speaker gets picked up by the right ear, and viceversa, a phenomenon-dubbed interaural crosstalk-that reduces the stereo-ness of the experience, and with it the sense of spaciousness even for coincident mic recordings. Headphones can solve the problem but they introduce another new problem: The sound seems to emanate from somewhere within the listener's skull, not from an external space like a concert hall or jazz club.

Polk, Carver and a few other companies took up the challenge of spatial realism in the "80s by, for example, supplying the right speaker with a "shadow" version of the left speaker's sound, timed and tonally shaped so that it cancels it at the right ear. Among the limitations inherent in Polk's early "Stereo Dimensional Array" and Carver's "Sonic Holography" techniques is the fact that the shadow signal not only appears, in this case, at the right ear, where it's needed, but also, at the left ear, where it's decidedly not. Modern digital processing, like that used in the "Panorama" in Lexicon's CP-series surround processors, can cancel this new distortion by supplying the left speaker with a shadow of the right shadow, then the right speaker with a shadow of the left's shadow of the right's shadow. It sounds crazy, but it works rather well, considering it really a new take on the old cat- chasing-its-tail theme, an provided you keep your head in just the right spot.

The Great Barrier Wall

Ambiophonics attacks the problem of crosstalk more directly by placing a barrier wall right down the center of the listening space to keep left speaker sound out of the right ear and vice versa. Glasgal's own barrier wall is an eight-inch thick absorptive affair made up of back-to-back RPG Abffusors. (Many much less costly materials are now readily available.) Whatever the construction, many listeners will recoil at the prospect of bifurcating their rooms with a 6-foot high sound wall that extends nearly to their noses. Glasgal hastens to point out that there are suitable, and easily movable folding acoustic screens available, and one may sit a foot or more from the end of the barrier depending on its thickness. Moreover, he insists that the prospective ambiophile has probably already stuffed a dedicated listening room full of obtrusive amps, speakers, cables, subwoofers and so forth, so one more aesthetic violation of the space can probably be tolerated-especially given the benefits in spatial realism that await.

Another distinguishing element of Ambiophonics encompasses a speaker layout that can only be described as deliciously oddball. Based on proven psycho-acoustic studies, Glasgal calls for the main (left/right) speakers to be positioned just a foot or two apart-typically separated only by the barrier wall-and firing straight at the listener. Another pair of front "proscenium" speakers, as Glasgal calls them, is arrayed flanking the main pair, so that each forms a 55ƒ angle left and right of the median barrier wall.

Citing extensive concert hall research, Glasgal explains that, "The average person's ears and head are constructed such that a sound coming from 55ƒ to the right of the nose, impinging on the right ear, will not produce a very good replica of itself at the left ear due to attenuation caused by head obstruction."

Thus, the proscenium speakers are positioned so as to deliver the most telling spatial cues with the least possible crosstalk. These "cues" are those sounds that, in a concert venue, are produced by strong, early reflections from the area immediately around the musicians, especially the stage walls.

Ambiophonics calls for at least two more pairs of speakers to play processed ambience and reverberation, one pair to the sides of the listener, and another in the rear. (Glasgal adds an additional pair up high in the deep rear to diversify the field still further.)

The final element of Glasgal's system is the electronic componentry necessary to turn conventional stereo (or even mono) fare from CDs, LPs, tapes and broadcasts into a multi-channel Ambiophonic feast. Although there are currently no 8-channel digital hall simulation processors available, there are several models that are powerful and flexible enough to contribute a piece of the puzzle. The preferred unit is the hard-to- find JVC XP-A1010-a digital soundfield processor based on comprehensive acoustic measurements of many of the world's renowned concert halls and opera houses. (Glasgal has also achieved satisfactory results using units from Lexicon and Yamaha in various combinations.) You'll need more than one processor to generate all the signals required for six or eight ambient speakers.

Formidable Odds

Whether Ambiophonics catches on is anyone's guess. It certainly has formidable odds to overcome. On the supply side, no one currently manufactures a one-box Ambiophonics processor. On the demand side, home theater currently exerts a lot more marketplace pull than a new technology tuned to classical, jazz and other acoustic music forms. And on the decorating front, there's that barrier wall to contend with-though it could be motorized to retract up into the ceiling when not in use. Glasgal himself admits that Ambiophonics' commercial appeal is limited to dyed-in-the-wool audiophiles (a shame for anyone who's heard it), and he doesn't plan on chucking his day gig as president and COB of a public company. He simply offers the results of his considerable research as a way for music lovers to move dramatically closer to that long-promised "concert hall realism."

For this music lover, it was worth the trip to New Jersey.