I found an older sub for sale locally. It had a very old 12”. I upgraded the driver with a new mc-300 driver from RBH. Their staff is the best in the business. My Frankenstein is now a new TS-12AN. The bass seems to much deeper than the 27 hz. I am powering with an RBH SAM-200. The sub is very agile with a tremendous warmth. It took only a few minutes to tune with my RBH MC-6CT towers. The 12 driver moves a tremendous volume of air the is felt as much as heard. I love passive subs due to so many issues with other brand active offerings. It will deepen with a bit of break in. @@@update@@@ After a few hundred hours of use, the driver has worked in fully, and the sound has changed significantly. It very deep, very warm and smooth as silk. It the best sub I’ve ever used.

Big and heavy, but still does not detract from a room, but a poor back will need help.