thanks for the compliment linkwitz. As for the drivers sounding any different since the build...not really. What has affected the sound more than anything has been re-orientating them towards the center to accommodate my new 84" screen...
Sooner than later I'm going to grab a mini dsp usb mic and find out what I'm getting, but on the whole I'm still enjoying terrific output and response- even in their current, less-than-ideal configuration. Personally, I'm very cautious about subjective opinions on how subwoofers sound
, to be honest- but I also realize it's all we have sometimes. With graphs out there showing significant in-room output well below 15hz with multiples of these, I really doubt there's a lot of merit for those claiming these do not offer terrific low bass...again, especially with multiples. Getting into the single digit 130db hz club is something many of us simply do not desire nor chase for many reasons, with my personal leaning being that it represents such a miniscule amount of available content that seems to erode a ton of value when weighed against the cost, time, and space requirements. YMMV.
As far as those considering a build, with diysoundgroup now offering great 18" cabs you merely assemble and finish them to your liking there's now a fantastic, stackable option for those who do not wish to go all the way with a bona-fide, ground-up DIY dual-build. If you do decide to go for a complete build, I'm quite happy with about 3.5 ^3's per cab...I know others have gone up to 4', sealed with some builds with great success.
Build-wise, I have found that a cab constructed of furniture graded plywood or baltic birch with a double front baffle, front to back bracing between the drivers, and a single 3" cross brace behind either driver creates a fantastically rigid, resonant-free cabinet. I realize others spend more time, money, and materials on bracing but I have yet to find that there's any real sonic benefits to it. To each, their own, though.
As far as amplification goes, I'm still very pleased with my Crown xti 4002- I find its 1600 watts per cab more than ample for my requirements...most could probably get by with even less/more economically for their space/listening habits.
Good luck with your build, I'm certain you will satisifed with the results.