Ok I'm ready to snapshow here...
I picked up this Polk sub on sale and ran home to toss it onto my Metallica Prem. Sub is plugged in, threw some alligator clips on 16ga speaker wire, clipped them onto the cab speaker, and ran the line out the cab to the high level inputs on the sub.
I get practically nothing.
I have to crank the sub full blast and up the x-over all the way to get anything, and at best it's some low notes you can barely hear unless your head is under the cab. I've tried reversing the leads, thinking I messed up my + and - but swapping them made it worse - low rumble that now doesn't match the music. I've tried left and right, I even tried bridging like movingpictures did - nada.
Wtf am I doing wrong? I feel like everything is hooked up perfectly but I just can't get anything going here. Either this sub is borked, or I'm an idiot and have unknowingly hooked something up wrong. Any advice which it is? haha I don't have any home stereo crap to test this thing out on so I'm at a loss as to what to try next...