I have a dd-12 and wrote about it extensively at Audio Asylum. I love this sub. Tight control of the bass, very musical, very fast.
I have a very small room and there are some issues with it. Before, i couldn't calibrate it very well to any sub I tried, and I tried a REL Strata III before.
The DD12 provides you with a remote, microphone, and video/audio eq outputs to connect to a monitor and your preamp. Once you establish the position in the room, turn it on and it'll start a frequency sweep between 15-200Hz that the microphone (placed at the listening position) picks up and displays the response on your monitor.
You then adjust the sub xover, slope (anywhere from 6db/octave to 48), phase, polarity, and servo control. Once this is done, you go back to the EQ screen and adjust the levels using a fully paramatric 8 band EQ. It's amazing. i was able to attain a flat response from 125Hz to 15Hz in my room. Bass has never sounded so musical.
The one caveat is that the DD series bass' is TIGHT. The active servo control keeps things controlled and i like this, but some may want more "boominess" that increased distortion can sometimes bring.
I recommend it highly!
