Speakers with a 360 degree sound. Read

I was at the Stereophile show in 1996. HSU found a way to get a 360 degree sound without losing midrange. As you know, Mirage and Definitive Technology make these bipolar speakers. Where drivers are on the front and back of the speakers. I always felt this design was flawed, because bipolar speakers didn't sound good in the midrange. What HSU did was, he used 4 PSB Alpa speakers as the main speakers. 2 mini monitors were facing foward and the other 2 mini monitors were right behind the 2 mini monitors facing foward, but these 2 mini monitors were facing the wall. HSU was using a Denon 5 channel receiver and a 2 channel amp for the surround speakers. The 5 channel receiver powered the 4 PSB Alpha speakers and the PSB Center channel and the 2 channel Amp powered the surround sound speakers. There was a 600 dollar HSU Sub being played on these speakers. Let me tell you, this system sounded great. It sounded so 3 dimentional and airy. I think HSU thought of a great idea, to place the speakers facing foward and then to use another pair of speakers facing the wall. This design will give you a 360 degree sound, where you get a great midrange.
Three questions:

1) What makes you think that this is different than Mirage / Def Tech or other similar designs where they use "back to back" drivers inside the same cabinet firing in opposite directions ?

2) What " 360* " speakers are you basing your "lost midrange" comment ? How were these speakers situated in the room ?

3) There is a BIG difference in something that offers 360* of radiation and a bi-polar design. Are you familiar with the differences in design ? Sean
To really appreciate a 360 degree speaker you have to sit cross-legged and say "Ohm".
mbl & german physiks also make 360 degree speakers, besides ohm acoustics.

re: bipolar sound, (which *is* a lot different than 360 degree sound), i always thought the comments of jim thiel were interesting when he said why he stopped prowiding bi-amping capabilities on his speakers. he said better results wood be obtained by having a second pair of his speakers situated directly behind the 1st pair, as hsu has done in their show displays. (i also heard the hsu room at the '96 s'phile show, but i was not too favorably impressed). personally, i don't much care for bipolar designs - too difuse a soundstage for me... but, done correctly, they can help eliminate sidewall reflections, as they tend to create a null at the sides. but, yure still faced w/dealing w/the rear-wall reflections.

i tink it's audio artistry that makes bi-polar speakers, but only for midrange & below, as they feel the hi-frequencies are directional enuff not to need this help, and this also helps eliminate the difuse-ness of full-range bi-polars. i've never heard 'em, but have always been intrigued by the idea...

doug s.

What a bipolar or omni speaker does is create a more powerful, diffuse reverberant field that also more closely approximates the tonal balance of the direct sound. The result is more realistic timbre, a less fatiguing sound (as the brain isn't working to integrate the direct sound with a wrong-sounding reverberant field), and often less precise imaging. At a given price point, the bipolar or omni speaker is competing with conventional speakers that have less of their budget devoted to multiple drivers and so can use better quality individual drivers.

The Audio Artistry speakers were dipoles, not bipoles, up to the tweeter. Maggies and electrostats are also dipoles. A dipole has, in my building and listening experience, a couple of advantages over biopoles and monopoles - namely, less boxiness and less room-induced coloration in the bass (except of course in the case of hybrids that use a conventional woofer).

Wolcott Audio makes an ingenius omnidirectional speaker that uses a single dome tweeter.
audiokinesis, please explain the differences between bi-polar & dipolar speakers; i've always thought these are pretty-much the same ting...

tanks, doug s.

Doug -

Ahem, sorry it's taken me so long to respond...

With a bipole, the rear radiation is in-phase, as in two woofers sharing the same enclosure, one on the front and one on the back, as in Mirage M-1's or Definitive Technology speakers.

With a dipole, the rear radiation is out-of-phase, as in Maggies or electrostats, and usually there is no enclosure.

The out of phase front and rear radiation of a dipole tends to cancel out the bass, so for a dipole to operate as a full-range speaker it needs a large baffle area (the larger the panel the lower the frequency at which cancellation sets in). Successful dipole designers find some way to equalize out a bit of that rolloff, and some use electronic equalization as well (like the Audio Artistry Beethoven). Because of the cancellation and equalization needed to restore flat response into the low bass, a dipole needs to have quite a bit of air-moving capacity to produce the same bass extension and SPL's as a conventional woofer-in-a-box system.

So why the heck bother to go to all the trouble and expense of a dipole? Because they sound so good. In the first place, there are no cabinet resonances or colorations. In the second place, the radiation pattern they produce is conducive to more natural sounding bass than a conventional speaker (which will have omnidirectional bass radiation). A dipole system will have a figure-8 radiation pattern in the bass - and so for a given on-axis sound pressure level, will be putting about 5 dB less bass out into the environment (this figure calculated by Sigfried Linkwitz, designer of the Audio Artistry speakers). So there will be 5 dB less excitation of room standing wave modes to muddy up the bass. If you read the reviews of large, well-executed dipole speakers (Maggie 20's, Audio Artistry Dvoraks or Beethovens, Gradient Revolutions, Quad 989's, Sound Lab M-1's or A-1's), you will find the reviewer always comments on how natural and musical the bass is. Dollar for dollar a conventional woofer system will play louder and deeper, but I have yet to hear a conventional system match the naturalness of a good dipole, probably because the radiation pattern acoustics overwhelmingly favors the dipole.
Have you heard the Shahinians? or Beveridge?; for me and what I have heard (have not heard the Mirage/DT stuff) these can't be beat for dispersion, seamless sound and large radiating patterns.
Happy listening