If you think you are going to block a sound wave with a wavelength of 20 feet with a panel of any size or type that you could fit in a room I would love some of the stuff you are drinking. Dipole subs will make lots of bass you can hear and will sound quite different if you move them just one foot. What they will not do reliably is make bass you can feel. It found favor with people trying to avoid cabinet resonance and complexity unfortunately it does not work. Having said that the best dynamic loudspeakers I ever heard were a D' Appolito array, two 5" drivers and a diamond tweeter on a sandwich of MDF and solid surface material with a 6db/oct crossover at 2K and a 100 Hz cross to a pair of 12" subwoofers.
The panels were hung from the ceiling on decorative chains. They were also home made! Brilliant.
Comb filtering is not much of a problem at higher frequencies. It is a huge problem in the bass (just another reason dipole subs do not work) The rear wave interferes most with image specificity. All you have to do is put acoustic tile on the wall behind the speaker and everything snaps into focus. Won't do a thing for bass performance which is why I cross to enclosed subwoofers.

