Too much power at bass frequencies damaged the voice coil. Overheating!
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Thanks, the JBLs I think are rated up to 300 watts and I couldn't have been sending more than 50 watts tops. I did hear some crackling during kick drums earlier on in the week, that could have been what did the woofer in.
But I am starting to think that this incident was due more to the age of the speaker (at least 20 years old?) than anything else.
My biggest concern is that I have something set up incorrectly between my preamp, integrated amp, and speaker system that could be damaging speakers and in the long run, components.
You mentioned, the woofer is, "stuck out". How far out? It’s possible that the voice coil left the magnet gap, got non-linear and caught the gap’s edge. Remove the driver, from the cabinet. Reach around the frame, with a finger and thumb on opposite sides and see if the cone/coil can be moved. If so- realign it and it might go back in the gap. It’s also possible, that when/if you exceeded the woofer’s max excursion(same scenario) you crushed the end of the voice coil. In that case, you’re SOL and in need of reconing. The noise you heard, was likely the voice coil hitting the magnet structure(possibly bottoming out). If it’s stuck and in the gap, roberjerman’s correct. Are you running with your bass boosted?
I suspect it could definitely be the 35 year old CL40 valve preamp that is the culprit more so than my 9 month old Luxman L-509X integrated amp. When the service guy comes over on Friday to replace my La Scala II tweeter, I'll ask him to measure the dc on the CL40 and the 509X.
The CL40 was totally restored (including new tubes) in 2013, but I think that's a much more likely scenario than the 509X.