bipoles/dipoles for music...

Off axis dispersion is one of the great attributes of rear driver systems...one can be almost 90 degrees off center and still hear the separation of instruments, etc...I also enjoy the increased depth and relaxed presentation which lends itself to vinyl reproduction....in other words...instead of brutally punishing a recording...these systems tend to focus on what the recording is doing well..

08-03-12: Phasecorrect
Off axis dispersion is one of the great attributes of rear driver systems...one can be almost 90 degrees off center and still hear the separation of instruments, etc...I also enjoy the increased depth and relaxed presentation which lends itself to vinyl reproduction... ...these systems tend to focus on what the recording is doing well.

Maybe that's part of why I can spend hours on end spinning vinyl through my Mirage OMD-15s. They are also the first speakers I've had that reveal inner detail well while keeping it in musical perspective. Separation of instruments and voices is probably behind that. In particular I noticed the subtle blending of wordless vocal backup effects that I often didn't know were there.

Anyway, the idea that rear-firing and omni speakers create an indistinct but large smear of what's on the recording doesn't match my long-running experience. You can hear deeply into the soundstage--and therefore--the recording.

With a well executed design, I suspect that there is less fatigue factor in general whenever all the sound is not being fired directly at your ears in the sweet spot. I think this generally lends itself to longer listening sessions, especially at higher volumes. At lower volumes, listening fatigue is less of an issue and it is generally easier to handle all the sound firing directly at you. At least, this would seem to be consistent with my experience.

1) Dipoles and bipoles are extremely different things. An acoustically small dipole has 4.8dB of directivity which means it's radiating 1/3 the total power of an omnipole for a given on-axis SPL. A bipole tries to approximate a monopole with 0dB of directivity.

2) Most "dipole" speakers are planers which are not acoustically small at higher frequencies and don't do a good job approximating an acoustic dipole with directivity breaking 10dB at high frequencies and all sorts of lobing that make for a narrow sweet spot for both imaging and correct tonality. You need to differentiate between those and speakers which act more like dipoles. Panel resonances are also an issue.

3) Conventional wisdom which holds that dipoles add more reflected energy to the sound than conventional speakers is incorrect. A conventional speaker starts off omnidirectional with 0dB and has directivity increasing with frequency to perhaps 10dB at the end of it's tweeter's pass-band. It generally doesn't surpass the dipole's directivity until 1-2KHz which we could approximate as the end of the human vocal range.

That's because although dipoles have more energy headed out the back they have less to the sides (-3dB at 45 degrees, -6dB at 60, -12dB at 75, etc.) which is friendlier for many listening rooms. When I eyeballed the numbers for one listening room I noted a 7ms delay for the front wall reflection that was -6dB for distance, 4ms off the ceiling at -3.5dB, and 3.5ms at -3dB for the side wall. Mix in dipole attenuation of -3.7dB off the front wall, -3dB off the ceiling, and -8.2dB off the side wall and it's obvious the dipole can color the sound less than a conventional speaker.

Using a decent dipole implementation (not a planer) you still get whatever sound stage is recorded without embelishments. You can use the off-axis roll-off to compensate for speaker distance as you move off one side so you can have an imaging sweet spot for several people. You also get no bass boost below the room's fundamental resonance and better modal behavior.

It works _spectacularly_ well for critical listening.