JBL 128H Woofer Refoam

[gary7]

Anyone do a refoam on JBL 128H woofs. I have a pair of L112's I'm fixing to refoam. The kit maker says the voice coil gap is to tight to not use shims. I have done several other woofers and did not cut out the dust cap with success. Anyone else foamed a pair with out shims or should I use them on these woofs. :scratch2:

 

[Sam Cogley]

You should really always use shims anyway. If you don't, the speaker might "work" but I don't see how you can ever really be sure the voice coil gap is truly uniform. "It doesn't rub" is just too imprecise a test for my tastes.

A test tone is another method of centering that works just fine. Depending on the driver, I'll use either method.

 

[tensleep]

I did mine in my 4410 Studio Monitors using no shims and the test tone method. They have been going strong for over 12 months now.

Here is a before and after and a link to the repaired thread:

http://www.audiokarma.org/forums/showthread.php?t=209776&highlight=jbl+4410

 

[BMWCCA]

Even more critical on the 128H is the size of the cone. JBL used several different ones. If they didn't specifically ask you to measure the diameter, you could have other problems beyond slashing your dust cap. Rick Cobb's kits work great, he specifies them based on your 128H cone, and they have never required shimming in my experience.

 

[Indynryder]

I have done 2 pairs of L166 12" woofers the most trouble
I had was with shimming & tone method. First set one shimm
one tone method. Not to mention the extra time it took.
The second pair used my old approach, which I have done
on many other brands, first adding lite glue on the cone &
foam when tacky adhear them togather. Second after waiting
about 1/2 hr adding extra glue (alittle more than the first step)
to the basket & the outer foam. Then apply quickly. While
still moveable (basket & foam) lightly pressing evenly &
lightly between the cone and dust cap.( This will even out
the outer edges of the foam.) while doing this you will want
to notice and make sure the voice coil doesn't rubb
(very noticeable) next let it sit for about 1/2 hr repeat
process. When done with this process lightly & evenly
press foam to basket. Through out this process lightly press
Down on the dust cap in the center as possible ( making sure
no rubb) the caps are quite durable and thick. Still be careful.
Most will scoff at this method. if this is your first time I
wouldn't recomend, this without practice. This method is
simple and quick I run my gear with a yamaha M-80
power amp 250w per ch. No hang ups or rubb. Good luck
although practice is better than luck.