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JBL LX 66 Woofer Repair

skaterblack

skaterblack

Active Member
I recently was given a pair of JBL LX 66 floor standing speakers. The woofers needed refoaming, and I did that. Then I tested them. One of the four woofers has a buzz. How should I proceed? I've rotated the speaker 180 degrees in the cabinet with no results.
 
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I've worked the foam free on the issue woofer. I'm wondering whether I can get it right this time or if it's an issue with the coil or even the leads?
 
Sounds like an issue with the refoam work on that woofer. The voice coil is out of alignment and rubbing. Will have to refoam that woofer to correct.
 
How did you refoam them? How, if at all, did you center the cone/voice coil? Some use shims but I use a 30 Hz tone with good results. I did one set by hand, but if you do it that way you need to be sure you're moving the cone evenly and that can be difficult.
 
teal'c said:
How did you refoam them? How, if at all, did you center the cone/voice coil? Some use shims but I use a 30 Hz tone with good results. I did one set by hand, but if you do it that way you need to be sure you're moving the cone evenly and that can be difficult.
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I did refoam it again, this time using a tone to try to center the voice coil. I had trouble finding a quiet spot, and the results were poor. I may get only one more shot at this before the foam will be unusable. Any last advice before trying again?
 
Using an exacto knife carefully cut off the dust cap and shim the vc with paper. If you cut it off close enough to the cone you can glue it back and will not be able to tell.
 
How did you do it?
https://audiokarma.org/forums/index.php?threads/new-surrounds-in-a-can.799283/#post-11088224

My scratching voice coil wouldn't allow a centered voice coil, I had to attach the surround to the cone first (my normal method) and adjust the angle with the surround until the scratching disappeared.
I used clothes pins to hold it's position until the glue dried. One side of the foam is narrower, the other a little stretched out, but it worked.
index.php

According to my last inquiry, my brother says it's still good. I'm still going to check it next time I'm over there.
 
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Possible the voice coil former on this woofer is not round anymore, or it has bottomed out due to overdriving, and the back end of it is bent over a bit, so it rubs. Could be difficult to get it to not buzz. Which is not meant to deter you from trying.

Or, it could have a shifted magnet, if it's one that is epoxied on. That would make the gap smaller than it should be.
 
skaterblack said:
I did refoam it again, this time using a tone to try to center the voice coil. I had trouble finding a quiet spot, and the results were poor. I may get only one more shot at this before the foam will be unusable. Any last advice before trying again?
Click to expand...

I had the same issue on my LX-66. Three out of 4 centred perfectly, the fourth getting scratching, no matter what.

I eventually took it to the pros at Speaker Doctors in Sydney who managed to get it perfectly aligned.
 
Success! Although I'd never done it before, I gave in, removed the dust cap, and shimmed the voice coil. Thanks kirkendoll and all others.
 
kirkendoll said:
Using an exacto knife carefully cut off the dust cap and shim the vc with paper. If you cut it off close enough to the cone you can glue it back and will not be able to tell.
Click to expand...
Success! Although I'd never done it before, I gave in, removed the dust cap, and shimmed the voice coil. Thanks kirkendoll and all others.
 
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