I have a pair of SDA SRS speakers that I bought new in the mid 80"s. They are powered by a Yamaha M-80 that I bought at the same time. For sometime now my speakers thermal protection has been cutting off the tweeters while listening at loud levels that used to be no problem. I contacted Polk about this before and they sent me some new thermal switches to install in my crossovers. That didn't fix anything. Could the problem be my Amp?