i would suggest you use a control relay. subwoofers pull alot of current and a normal switch isent rated for very much current flow. basically, your relay operates like a switch. only difference is your using a switch to actually control the coil in the relay. you hook a switch up normally only you put the relay coil either before or after the switch (I'd suggest after) when you toggle the switch the coil gets energized pulling the plunger in and turning the normally open contacts to normally closed (just how a normal switch works) this turns your subwoofer on and off without heating up the contacts on a typical switch. just make sure your control relay can handle the current, they normally say on the top of the relay what its rated for. there prolly have to go to a automotive shop to get them, normaly relays run on A/C and i dont ever work with DC operated relays but i know there out there. (I am an Electrician). the main issue there is the fact that A/C produces inductance while D/C does not, thats the primary way the contacter i just explained works.