Your kid borrows the car, blasts too many techno tracks, and blows out the subwoofer. It used to be that you’d have two choices: Buy a new one (woofer, not kid) or put up with a hoarse bass line. But when a subwoofer pops, it’s usually only the voice coil—the part that drives the cone—that’s burned out; the rest of the assembly is just fine. Boston Acoustics’s SPG555 subwoofer is the first with a replaceable voice coil that you can install yourself.