bipoles/dipoles for music...

I would use the terms focused versus unfocused imaging to realistically assess imaging performance.

Bipoles and dipoles are capable of a focused presentation I believe as are omnis, however the presentation is often (not always) different from say a good pair of monitors.

Ratios of direct to reflected sound is a discriminating factor. Bipoles/dipoles are different than most conventional box designs in this regard but setup including distance to walls also comes into play (except perhaps in an anechoic chamber) and might be done differently for different speaker types depending on the target results desired.

Time coherency across the audible sonic spectrum at any particular instant is a related but different sonic artifact that factors into quality imaging. Not sure bipoles/dipoles ae categorically any better or worse than other designs at this aspect either.

Not a fan of multiple drivers firing front and back.

Nice summary by Johnnyb53.

Agree with atmasphere.

The principle applies to all speaker designs and home sound reproduction in general and is affected by both room acoustics, dispersion patterns and speaker placement relative to walls.

Bipoles/dipoles/and omnis just have different dispersion patterns and leverage it to a greater extent.

However you achieve it, a larger soundstage is like a big screen TV. Assuming all else is well, there is less congestion and more "room to breath" which makes it easier to focus in on specific elements of the recording as desired and also enhances the overall musical experience in that sound is a 3 (actually 4) dimensional phenomenon and requires space in order to be reproduced accurately.

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.