Well, I believe that we have digressed entirely from my original ‘post’.

In my 75+ years, starting in the 60’s, I have built Heath and Dynaco kits, both audio and analyzers; I have also built and/or modified a number of loudspeakers and cross-overs (with the help of LEAP). I currently have a number of audio systems (all stereophonic) including my old Dynaco ST70 Amp/PAS3 Preamp/FM tuner, plus Phase Linear Amp and Preamp, Adcom, Hafler, etc.; I also possess Duntech PCL 3 speakers (excellent), Magnepans, ESS Transtatic I’s (old,1972, but still produces one of the finest sounds around . . will empty your cupboard and rattles your doors at 15 Hz, and the ultrasonics will drive your cat insane), and KEF LS50’s (for background music).

My original ‘posting’ was to determine the optimum height of this downward firing subwoofer above a wood floor. My experience indicates that with such an arrangement the floor actually becomes part of the speaker, with respect to both driver/vent loading and vent length/action. I have a 65” SONY Bravia TV with built-in, front mounted 3-way speakers, supplemented with the SONY wireless sub. This 8” sub produces better, cleaner (if not as deep) bass than the Ultra X-12: a bass drum has ‘impact’ and is taut, versus X-12’s ‘muddy’ sound (as if was under a blanket!).

My wife likes the appearance of the X-12 so if I cannot obtain better, cleaner bass from it I will probably gut it, invert it, Drylok it and make it into a planter. I have already spent too much time and effort on this subwoofer.

Thanks for your replies, though.