[Jazzman53]

Has anyone seen the Modal Akoustic Subwoofers?  It's a Ripole design which should work really well with dipole mains:

[firewall]

From the manufacturer's website:

" Because the dispersion of a RiPol does not follow the classic 8-shape, a RiPol is not a typical dipol but one of its own kind. Dispersion diagrams show clearly the difference compared to a classical dipol, which justifies its own name, RiPol (as a combination of "dipol" and the last name of its inventor, Axel Ridtahler)."

Sadly, this means that it does *nothing* for dipolar speakers.

I run SVS woofers and they blend well with my Maggies.

[Jazzman53]

For me; Ripole subs work exceptionally well with my dipole speakers. 
   
My speakers are full-dipole hybrid ESLs, with triangular base legs forming a tapered H-baffle around the 12” woofer.
       
I had been using sealed box subs, but even with a DSP crossover and parametric EQ's, I could never get a seamless blend or the tight, clean, non-booming bass I wanted.  Adding corner bass traps to my room only helped a little.

A few years ago I replaced the sealed box subs with a pair of 2 x 12” Ripole subs and magic happened!
The booming and muddiness was GONE-- leaving only clean, tight bass rising up from nowhere and receding back to nowhere-- quite amazing, really.
   
The Ripole radiation pattern is not a symmetrical figure-8, as in a true dipole, but an asymmetrical cardioid with the front lobe being more pronounced.  Yet, they have a similar off-axis null.  And whereas a dipole baffle does not change the woofer’s FS, and a sealed or ported box raises its FS significantly, a Ripole lowers the woofer’s FS by about 10Hz!  And the more compact you make it, the lower the FS! 

With the sealed box subs; I experienced the sound as a first arrival followed by successive arrivals reflected from the room boundaries—all combining to render the sound loose, ill-defined and slow to decay.  And their omnidirectional propagation excited my room's resonance; resulting in booming one-note bass.

Ripoles significantly reduce the aforementioned nasty effects, I believe, because their off-axis null doesn’t excite the room resonance, and I'm hearing predominantly the front lobe sound, as the off-axis response is nulled and the opposite-phase rear lobe gets mostly cancelled. 

The downside is the low efficiency (I consider a pair of 2x12’s more necessity than optional).  Their impact is a bit softer but the decay very fast, which I believe explains the tight, clean and unobtrusive quality that’s great for music but not so much for home theater special effects.   

For me; the Ripoles were ideal for my setup.  Call me biased and I won’t disagree, but I'm not going back to conventional subs.