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What the H ll Happened Here?

I was listening to music two nights ago and heard what sounded like low level scratching through one speaker, then it went away. A short while later it happened again but this time the sratching was coming from both speakers with reduced bass response. Then, I lost bass in one speaker completely with maybe 1/2 output from the other. Tweeters seem OK but hard to tell as they sound kinda bad without the rest of the spectrum.

By the way, I have Harbeth C7s which are two ways.

I thought the problem may be tubes in the pre-amp so I plugged in a passive that was just boxed away, same problems. Tried another amp, CD player (with and without the DAC), same problems. Swapped speakers from side to side, problem with woofers went with them. Then I tried pressing slightly on the woofers, doing so causes changes in the distortion. So I'm pretty damn sure it's a problem with both speakers, but what the hell happened? And to both speakers at the same time?? I noticed no electrical surges, power problems of any kind.

Guys, any ideas as what's going on???
tomryan

Showing 1 response by rockvirgo

rockvirgo
587 posts
 
Your voice coils may be shorting out in contact with the magnets. Maybe burned or melted from extreme use? The crispy bits could cause interference. With the amp off, and lightly pushing the woofer cones inward through their travel with your splayed fingers, can you feel the scratching of the voice coils in their gap? They ought to travel freely and be noiseless.

I had a pair of Dynaco A-25 10" woofers that both evidenced scraping behavior after about 30 minutes of play. When they were cold they acted and sounded fine. The problem arose after taking them from prolonged hot attic storage. I attributed their failure to corrosion but never tore them apart to see for sure. Please post the solution if you find one.
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