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.
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.