Bojay

I recently had a lightning storm and something happened to my home theater system, namely my KSW-300 sub. A low frequency popping noise comes from the sub when I do any of the following: 1.) turn the sub off to on. 2.) while the sub in on I change inputs from my amp. 3.) while the sub is on I change channels on my satellite dish receiver. Does anyone have any suggestions what could be the problem? Thanks for any suggestions.