Trying to build dipole sub - a la Celestion 6000

http://gr-research.com/sw-12-16fr.aspx

http://www.aespeakers.com/

However, you may want to look for some form of equalization for the 6 dB rolloff, perhaps DSP. There's Digmoda that has built-in DSP on their plate amps but, of course, plate amps aren't all that convenient for dipoles.

Should add that Madisound offers a service to precision cut the wood.

For this purpose, there are some pro amps that offer gain control, delay, crossovers and DSP along with gobs of advertised power for between $500 and $1000. Crown XTi series, Peavey, Powersoft, etc... Even saw that one had RCA's.

The reason you don't see much of this is because there's not many crazy enough to try. "Dipole subwoofer" is about as close to an audio oxymoron as an unbiased opinion.

Maybe I was a bit harsh with that oxymoron statement. The point was that deep bass (20 Hz) may be impractical with dipoles and that moderate bass (40 Hz) is possible but requires double the drivers as a conventional monopole. The other concern with dipole subs is the excursion of the drivers.

I also made a mistake. Meniscus Audio, not Madisound, offers custom baffles/boxes.

In your particular case, a crossover around 173 Hz is a bit of a problem. If you look at the Rythmik/GR amps, they are limited to 120 Hz. Contact Rythmik whether this is defeatable. Then, you're looking at your Behringer as a crossover again. That's also a fairly high crossover for summed left/right output.

Personally, the concept of the drivers facing each other seems counter-intuitive for a dipole. The effect would be much the same as a boxed speaker. Ya, I can see how it bring more control to high Q drivers and reduce that boomy
sound. The "Direct Servo", along with suitably designed drivers, ameliorates that condition to some degree.