Giving thanks for good audio...
It wasn't exactly your typical Thanksgiving, but finally after about 6mo of work on and off, I finally put the finishing touches on my dipole subwoofer project via some circuitry tweaks.
So, you are asking yourself, what exactly is a "dipole" subwoofer? In short it is a bass speaker that generates sound out of the front and back - only the back is out of phase relative to the front. Dipole subwoofers, in snobbish circles are considered one of the cleanest and most musical sources of low frequency sound due to the way they interact with the room - those boomy and dead spots are largely eliminated amongst other signature sonic characteristics. (aka they behave more like a real musical instrument - say a kick drum which radiates in a similar manner)
Unfortunately they are commercially very rare due to a fundamental tradeoff between crazy large size ... or massive amplifier power requirements - to both!. Most designs end up striking a balance, such as mine, retrofitted into some heavily reinforced and completely refinished 1960s era oak speaker cabinets:
Front and back views. Note how the back is totally open to the room unlike your conventional speaker
These do look fairly large - however they are actually on the smaller side of dipole design - and this is one of two cabinets! So as I said before, not very commercial. Since they are "small", the next magic trick is to compensate for the inefficiency with some electronic circuity sitting in front of a beefy power amp which is what I touched up this weekend - and can be seen in the picture at the top. After all is said and done, the acoustic *and* electrical models combined yield fairly good results:
The blue line being perfect, the red the full modeled "real world" response, so if you slide the red line up 6dB it follows the blue very pretty smoothly to nearly inaudible bass @ 30Hz before taking the inevitable plunge. That's pretty good.
So far VERY happy with the sound - largely as expected from all the mockups - and yeys - and not too hideous looking all things considered. (at least I think - lol)