I am trying to diagnose the recent issue with my 96 850 SC 815 stereo. My car appears to have the factory amplifier (so says the window sticker) and it clearly has much more punch than the other 850 premium stereos my other cars have. My issue seems to be that when the volume is raised (mildly loud, probably just right for my kids) or when the base is heavy in a song, there seems to be a harsh electrical "pop" that will come over the speakers as the music plays. It will sometimes match the base beat of a song. I immediately adjust the volumes hoping not to damage anything. It also seems to happen with CD's not FM radio. CD's play at a much higher sound quality so that could be the reason only they are affected.

Anyway, I seem to recall something like this years ago when I did my old VW up with a nice stereo and amp. The amp can't handle the power??? Not sure if that is the issue or is it something as simple as the speakers being blown by the previous owner. Any way to check speakers for damage? Is a damaged speaker always visible? I can't tell if the speakers are all experiencing the "pop" sound but it appears they are.

It is such a nice factory system especially from 1996. Any suggestions is greatly appreciated.
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1996 855 TL Platinum Ed., 1995 854 GLT 5 sp, 1995 854 (RIP), 2005 V70R (badly missed)