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Why Doesn't It Sound Live?

Posted by crutschow (A) on March 21, 2007 at 10:16:50

I’m in the process of setting up a new home theater which will serve double-duty as my music setup. After much research into many different speaker designs I have come to a conclusion about replicating the sound of live music, discussed below in some detail. It's sort of a grenade tossed at present standard audio speaker designs. But will it explode or just fizzle? If it does, the sounds you hear are exploding box speakers.

Until recently it had been a puzzle to me why it was still generally easy to tell the difference between live music and reproduced music, even though the quality of the source material, amplifiers, and speakers has significantly improved from my young days with tubes and vinyl (subjectivist tube-and-LP loving audiophiles notwithstanding). Although audiophiles often go to great expense (including such snake oil products as magic power cords, HiFi fuses, and exotic cables) to strive to get ever more accurate music reproduction from their box speakers, there is still usually something lacking in the end result that prevents the music from sounding “live”. Perhaps that’s part of the reason for the never ending pursuit of better fidelity, sometimes to ridiculous lengths. The listener is aware something is missing and thinks it’s some lack of fidelity, when perhaps it’s really just a lack of the live music ambience. They have a desire for this ambience, even if it’s not recognized as that, and the hope that it will somehow appear with the next small increment of improved fidelity, that fractional dB improvement in frequency response flatness or small percentage of distortion reduction or more power output or…. But, with typical box speakers, I now consider that a futile pursuit.

After reading numerous reviews and articles about speakers, and in particular, information on The Audio Critic and Siegfried Linkwitz’s websites (which I consider to be two of best sources for accurate speaker information on the web), I believe I now understand the puzzle of the live music sound. To recreate (not just reproduce) the sound of live music in one’s home, high fidelity sound alone is not sufficient. Indeed, I suspect that one can probably have reduced fidelity and still perceive sound as live, though with the flaws in fidelity apparent, if the ambience clues are correct. (The optical analog of this is looking through a pair of smeared glasses. You perceive a real appearing, if blurred, image, even though it has low optical fidelity, because the 3D clues are still there.) The ear-brain uses reflected sounds to determine the structure of the sound in space and these have a characteristic pattern for live music. Speakers that recreate this best in a normal room appear to be those with a dipolar or omnipolar radiation pattern where the patterns are reasonably uniform up to at least 3 kHz. These generate the proper room reflections that are interpreted as having the character of the original music sound stage, giving that U-R-There feeling of live music. Of these two radiation patterns, the dipole would seem to be preferred for having less interaction with room acoustics, but as the Pluto speaker design by Mr. Linkwitz demonstrates, an omnipolar pattern can also be effective.

Only a few other available speakers exhibit these radiation patterns. Examples are the Magnepan dipolar planar speakers, the Orion dipolar speaker designed by Mr. Linkwitz, and the omnipolar Ohm Walsh Speakers. All are reported to give a wide, realistic sound stage (although the Magnepans are directional at higher frequencies due to their large flat radiating surface which tends to reduce their sweet spot).

The old Bose 901 Direct/Reflecting speaker dating from 1967 (amazingly still available from Bose) was on the right track, but generates too much reflection from 8 rear speakers and only 1 front speaker. Bose based the reflection percentage on concert hall acoustics, but with this value in a typical sized listening room with its much shorter reverberation times, the sound at the ear is overwhelmed with multiple reflections (think hitting a golf ball in a tile bathroom). This muddies the virtual sound stage. It’s apparent that if a dipolar or omnipolar radiation pattern works well with 50% of the radiation directed to the rear hemisphere then 89% is way too much.

Standard “monkey coffin” rectangular box speakers, large or small, with forward-firing dynamic drivers, have a frequency dependent radiation pattern. They radiate forward in a unipolar manner at higher frequencies and approach an omnipolar pattern at frequencies below a few hundred Hertz. Even if a box speaker reproduces the sound with perfect fidelity, the reflection versus frequency from its radiation pattern in a normal room is atypical of live music and this is readily recognized by the ear-brain as music from a box. It will never really sound like live music. Of course one can still enjoy such music, as we all do, even without the live music ambience, perhaps by learning to accept (or ignore) the box speaker radiation pattern. It’s a personal preference as to the importance of the live ambience to your music listening pleasure. But I suspect it may be more important than many people realize unless they’ve heard speakers that produce the effect. To me, it’s essential, since I believe the holy grail of high fidelity is recreating the essence of live music, not just the sound. Of course that eliminates all the loudspeakers made which exhibit the box radiation pattern. And that would seem a rather disconcerting conclusion for the many box speaker manufacturers and owners. It requires a new paradigm for them as to what constitutes the best way to recreate the sound of live music. Box speakers RIP.

(For a related discussion see the Orion review and the subsequent Postscript comments in the Audio Critic website at http://theaudiocritic.com/blog/index.php?op=Default&postCategoryId=1&blogId=1

P.S. Based upon all this I have decided to buy six dipolar Magnepan MMG-W’s for my setup.

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