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JBL Speaker Refoaming

Looking good!

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Very nice job. About 30 years ago, I got to go to the JBL factory for field service for the HIFI company I worked for. They used a bostech MEK solvent based glue, and MEK can be used to remove old glue (MEK is a very volatile and strong solvent - care and ventilation are required). They had a rotating potters wheel to work on, which made it easy to rotate and clean off old glue on the surrounds. Biggest hassle was that the glues would soften up the foams, so would get wrinkles if you were clumsy or unlucky. They had different gap gauges to check roundness, and would tap the magnets with a mallet if gap was slightly out of round. Paper spacers of different thickness were used to shim most of the woofers with larger gaps, and some of the smaller diameter gaps had plastic cylinders for shims. One thing they were always particular about was making sure there were no chips or metal in the gap - they used a reversed piece of masking tape to clean gaps. At the time, almost nobody did refoaming - the factory recone kits were cone, voice coil surround and spider already assembled and ready to be glued for field repair. Steve
 
We have lift off! One of the best sets of speakers that I have ever listened to!
The $5.00 Dynaco A25XL's are having a look (that's another story). Vintage JBL's can bring it on.

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Fantastic work Terry,

The JBL's have had over 20 hours of running in and the sound has improved...

Everyone that has heard them has sat and listened.....and that is a first in my house....

Best speakers i have ever owned......
 
Excellent thread, this should be stickied. :thmbsp: I must be pretty lucky, I did my 125-As (?) from the L26s without shimming or a test tone, but they came out great. I would have MUCH preferred looking at your pics first. :yes: You're right, vintage JBLs kick butt. I'm also lovin' the little 4401s. :smoke:
 
sregor said:
Very nice job. About 30 years ago, I got to go to the JBL factory for field service for the HIFI company I worked for. They used a bostech MEK solvent based glue, and MEK can be used to remove old glue (MEK is a very volatile and strong solvent - care and ventilation are required). They had a rotating potters wheel to work on, which made it easy to rotate and clean off old glue on the surrounds. Biggest hassle was that the glues would soften up the foams, so would get wrinkles if you were clumsy or unlucky. They had different gap gauges to check roundness, and would tap the magnets with a mallet if gap was slightly out of round. Paper spacers of different thickness were used to shim most of the woofers with larger gaps, and some of the smaller diameter gaps had plastic cylinders for shims. One thing they were always particular about was making sure there were no chips or metal in the gap - they used a reversed piece of masking tape to clean gaps. At the time, almost nobody did refoaming - the factory recone kits were cone, voice coil surround and spider already assembled and ready to be glued for field repair. Steve
Click to expand...

There is a great video on youtube about speaker production at JBL at about the time my speakers were made.......take a look, it shows the revolving potters wheel glue applying method.......

http://www.youtube.com/watch?v=WXiwxir9xRk&playnext_from=TL&videos=uefGmVa3LDU
 
spaceman said:
Excellent thread, this should be stickied. :thmbsp: I must be pretty lucky, I did my 125-As (?) from the L26s without shimming or a test tone, but they came out great. I would have MUCH preferred looking at your pics first. :yes: You're right, vintage JBLs kick butt. I'm also lovin' the little 4401s. :smoke:
Click to expand...

JBL rules !!!!!

:banana:
 
This recalls my first refoam job 12 months ago, on a free pair of JBL L110's rescued from a dumpster. This is so familiar, except I used Rick Cobb's 30 Hz tone instead of shimming. They turned out fine, except it took me forever to scrape that old surround glue out of the channel in the woofer basket. Mine did not have the rubber O-ring on the outside, rather a fully slotted recess around the perimeter. I listen to them every day.

Further Note: I just looked closely at mine, and I'll be damned if that plastic perimeter ring isn't there. No wonder I thought I had a perimeter slot instead of an edge, and such a pain in the ass to clean off the edges. I'm lucky I was able slip the surround edges into that "slot", stick, and seal. I am a moron.
 
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