due to the Monsoon speakers being designed to work with the Monsoon amp, you have three choices. You could find a used replacement woofer and install that. This would be the easiest thing to do. Second, you could buy a replacement aftermarket woofer (or pair and swap out both sides) but it may sound funny. The Monsoon speakers have a lower impedence than normal 4-ohm speakers and they are mounted to a plastic baffle so you'll need to make MDF trim rings. Third and hardest, you'll need to replace everything. All the speakers and the Monsoon amp. If you have no other plans to upgrade the stereo anytime soon, I recommend just replacing the speaker with a used one. You can find them in the classifieds all the time and 1 speaker should cost about $15-20.