Wrapped the subwoofer in sound deadener...
I’d like to say that I can hear the difference, but no discernible change to my untrained ear. Maybe a bit less vibration...
Regardless, hardest part was getting the seatback pulled forward on my Super Cab truck. Very tight fit, and no side release like there is on the passenger side. Once I figured out the correct part of the release mechanism to pull up it wasn’t too bad.
I rigged some blue hobby wire as a temp fix; bought some thin wire rope for a more permanent solution since I’m all out of bicycle brake cable at the moment...well, any not in use anyway! Will make a simple loop around the release secured by a ferrule, and have it retained by the headrest post with another loop, ferrule, and stop.