I am starting to reasearch for a DIY project for high efficiency speaker for use with SET amps. Looking at your in-progress cabinet, I am curious as to what bass cut-off frequency have you tuned your cabinet to be? Is it possible to tune a 15" woofer to reach 25hz if ever cabinet size is no problem? what is the outside dimension of your whole cabinet? are you using SET amps? I am new to DIY projects and need some help. Whats xover are you going to use? Is it o.k. to use professional electronic x-over?thanks for any input! MERRY XMAS!!