PRESS AND HOLD "CTRL" AND PRESS "+" TO INCREASE TEXT SIZE.
There is no need to write in all caps.
As far as this "sub" input impedance, as James said, it's not published and is not very relevant since the sub comes with its own amp. If your goal is to replace the amp plate, I suggest looking into another direction, as this subwoofer's performance isn't stellar even when new.
See his review here:
The Polk HTS 12 is a 12” ported subwoofer with some innovative tech that allows it to produce clean, tight bass at a retail price of $549 that bellies its specs. Read our review.
www.audioholics.com
Read between the lines as James tries to stay as positive as possible.
btw: The author of this review (and many others as well) posts on these forums as shadyJ ;-)