Introduction

Ambiophonics, 2nd Edition
Replacing Stereophonics to Achieve Concert-Hall Realism

By Ralph Glasgal

Founder
Ambiophonics Institute, Rockleigh, New Jersey, www.ambiophonics.org

Dedication

To Johann Sebastian Bach, Richard Wagner, Gustav Mahler, and Lauritz Melchior, without whom we would never have bothered and to Manfred Schroeder, Don Keele Jr., Bob Carver, Yoichi Ando, and Ole Kirkeby without whose collective research we would never have succeeded.

Ambiophonics: Recreating the Concert Hall Experience at Home

There are essentially only two ways for music lovers to enjoy music performed for them on traditional acoustic instruments. One is by going to a concert hall or other auditorium, and the second is by staying home and playing the radio/TV or a recording. This book and the techniques it describes are dedicated to helping you make the home music-listening experience as audibly exciting as the live experience. Those audiophiles who share the dream of recreating a concert-hall sound field in their home, and who constantly strive to create a sense of "you-are-there," we have christened "ambiophiles". We call the science and technology used to create such an acoustic illusion "Ambiophonics".

Barry Willis wrote in Stereophile Magazine (August, 1994), "The idea that any musical event can be reproduced accurately through a two-channel home-audio system in a room that in no way resembles the space in which the original event took place is ludicrous."

Mr. Willis was absolutely correct in this when he wrote those words, but is much less so now, because Ambiophonics successfully works and its purpose is precisely to make the home-audio room resemble the space in which the original event took place. He goes on, "At present even the best discrete multichannel surround systems can offer only an illusion of being there." Experienced ambiophiles (a rare breed) would agree, but would also point out that surround sound is deliberately designed to produce the illusion of "they-are-here-around-you" which, while exciting for movies, is always going to be the antithesis of "being there". Finally, thoroughly despondent, Mr. Willis writes, "Tonal accuracy is the best that can be hoped for in a traditional audio system; true spatial accuracy will never happen. Audio products should come bearing this disclaimer: WARNING: IMAGE PRESENTED IS LESS THAN LIFELIKE."

The rest of us need not despair. Ten years of experiments have been devoted to demonstrating that "lifelike" can happen, and with exceptional fidelity to the original, from just two standard LP or CD channels. As hard as it may be to believe, Ambiophonics works better with two recorded channels than other techniques such as surround 5.1 can do with multi-mic, multi-channel media such as DVD where music is concerned. Yes, the Ambiophonic method described in this book may not always precisely duplicate a particular hall, but it can create a hall and a vibrant stage that could exist architecturally, that rings true, and is lifelike enough to mimic a good seat at a live musical event.

Many, if not most, serious audio enthusiasts presently believe that it is possible to achieve a solid stage image that may even extend beyond the loudspeaker positions, by employing the usual arrangement where two loudspeakers and the listener form something close to an equilateral triangle. They have faith that the perfect loudspeaker, amplifier, CD, LP, or 96/24 DVD player, and special cables will produce that wide, sharp imaging, stage depth, and ambient clarity that we all seek. Many also believe that audiophile-grade equipment, properly selected and tweaked, combined with signal path minimalism is more likely than simple acoustic listening room treatments to produce a higher fidelity sound field with enhanced width and depth. Some audio hobbyists prefer to listen primarily to small ensemble "they-are-here" small jazz-combo sounds such as found in the Chesky catalog and thus have no need or even desire to achieve a realistic orchestral or operatic sound field. They feel strongly that large scale symphonic or operatic classical sound reproduction is not what the high end should concern itself with and this view is reinforced at hi-fi shows and showrooms where almost all demos use recordings of small combos, often consisting of just a voice, a guitar and a little percussion. Many devoted home listeners also hold that the rear hall reverberation captured by the recording microphones is being properly reproduced when it comes, together with the direct sounds, from the front loudspeakers.

A new breed of video-age audiophile is in the majority and is convinced that hall ambience, extracted from specially encoded or directly from multichannel recordings and steered or fed to two or even four surround speakers can achieve the "you-are-there" illusion. This latter group is at odds with those who hold that any such processing or non-minimal microphone techniques is anathema.

Considering these prevailing and conflicting conceptions and misconceptions, it is remarkable how good, and even exciting, a sound can be produced by such ad-hoc equipment and still basically stereophonic methods. The musical sound generated by products from the overwhelming majority of serious stereo reproduction equipment manufacturers is truly first class as far as it goes. But the traditional methods of deploying this superb equipment at home has reached a dead end as far as closing that last yawning gap between perfect but flat fidelity and true spatial realism.

I believe that Ambiophonics not 5.1 or similar surround sound method is the logical successor to Stereophonics. I also believe the majority of serious home music listeners are closet ambiophiles who really want to be in a realistic, electronically created concert hall, church, jazz club, theater or opera house when listening to recorded music at home. The purpose of this book is to pass on the results of the research and experiments that I and others have performed. Ambiophiles everywhere can take comfort in the fact that it is both theoretically possible, possible in practice, and reasonable in cost to achieve the formerly impossible dream of recreating a "you-are-there" soundfield from standard unencoded LPs, CDs or DVDs in virtually any properly treated room at home. In Ambiophonic parlance, when we say "real" we mean that an acoustic space of appropriate size and stage width has been created that is realistic enough to fool the human ear-brain system into believing that it is within that space with the performers on stage clearly delineated in front. The nice thing about Ambiophonics and existing two channel recordings is that so-called stereo recordings are not inherently stereophonic. That is, the microphones act like ears. They don't know that their signals are going to be played back in an untreated room and subjected to crosstalk, pinna angle distortion, and the other ills described below. Thus virtually any two channel recording of acoustic music, unless panned or multi-mic'ed to death, will respond well to Ambiophonic processing and reproduction.

The Ambiophonic techniques described in the following chapters produce a sound stage as wide as that seen by the recording microphones, an early reflection sound pattern that defines the hall size, and the character of the recording space, the listener's position within that hall, and a reverberant field that complements the content of the music and the original recording venue.

Although Ambiophonics does not rely on decoders, matrices or ambience extraction, it does incorporate commercially available digital signal processors, which are essentially special-purpose computers, to recreate the appropriate ambience signals. It is therefore a prime article of ambiophile faith that while such signal generators are always subject to improvement, they have already reached an audiophile level of performance if one uses them Ambiophonically as described in the chapters that follow. It is also not the belief of the author that there is only one fixed way to achieve the Ambiophonic result. But I believe the Ambiophonic principles enumerated below can form a better foundation to build on than the now seventy-year old stereo and its unfortunately, closely related, surround-sound technology.

In brief, Ambiophonics uses room treatment, radical front channel loudspeaker positioning, computer recreation of real, early reflections and the later reverberant fields, and additional loudspeakers, strategically placed, to accurately propagate such ambience. Not every audiophile will be able or willing to do all that I suggest, but as each feature of the Ambiophonic system is implemented the improvement in realism will be easily audible and clearly rewarding.

If any science can be called ancient, acoustics is certainly one of them. The literature on acoustics, concert-hall design and sound recording is so vast that I am prepared to concede in advance that no individual fact or idea in the chapters below has not already appeared, at some time in some journal. I can only hope that the concatenation of all the ideas and devices that define Ambiophonics has some modicum of novelty. While I don't need to credit pioneers as far back as Helmholtz and Berliner, I would like to acknowledge my debt to such relatively recent researchers as W. B. Snow, James Moir, Don Keele Jr, stereo dipole-ist Ole Kirkeby, Manfred R. Schroeder, and his former colleague Yoichi Ando whose ideas on how to build better public concert halls inspired me to adapt his methods to create fine virtual halls for at home concerts.

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