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Dennis, I am no expert but it seems if you are having intermittent problems with your system it wouldnt be blown speakers. I dont have the Bose system but if it has rotary controls they may have dirt in them. If they do, try some electronics cleaner in them to clear dirt/dust from the contacts. There is also the Audio/Electronics forum under the "General" section. You might ask there.
My Bose symptom in my 1993 was incredibly loud popping after the radio was powered up. Made no difference where the volume was set. Incredibly load! I found this after I wondered why I couldn't hear from the left rear speaker and found it disconnected. Once connected then I knew why!
I replaced all the electrolytic capacitors on the amps (all were experiencing varying degrees of electronic leakage and some had physical case distortion). Then the Bose chip was found to be bad and I imagine from the cap failures. The caps for two amps cost about $20 from Digikey and a buddy ordered the Bose chip for me. Not sure how much or from where but he volunteered and I accepted. Works great now.
But let my cut to the bottom line. It's common knowledge that the capacitors are changed to fix an assortment of problems. Popping and squealing are common and that can be any one of a number of the de-coupling capacitors.
But there is only one electrolytic capacitor that actually has signal (audio) flowing thru it. When it gets weak the sound gets bad. It is labeled on the board C172 which is a 10uf @ 16 volts. If it is a cap, that’s the one.
Other than that, could be a bad speaker but there are high quality and never heard of anyone replacing a speaker.
You can exchange the left and right enclosures for test purposes just to verify it is the box you suspect.