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View Full Version : Is it really necessary to shim the voice coil when replacing 2235H surrounds??



Tweak48
05-30-2016, 12:13 PM
It's time to replace the surround on my B-380, and I'd really rather not pull the dust cap off unless absolutely necessary. I've replaced my 15" Tannoy surrounds with no problem, but I understand JBL voice coil gaps are extremely tight. I'd like to avoid pulling the cap to use shims, but a rubbing voice coil is no good either.

So what do people around here do when installing new surrounds? Thx.

1audiohack
05-30-2016, 02:05 PM
I recently replaced the surrounds on my 4435's. I cut off the dust caps and replaced them when done.
I think it's the right thing to do. Working around the mass ring is something I didn't have to worry about with the 2234's though.

The caps are less than $5 each from JBL and it is easier to put a new cap on the old glueline than a new cap on a new cone.

Can you do it without cutting off the dust cap? People do it all the time.

All the best!
Barry.

Chris Brown
05-30-2016, 04:50 PM
Yes it can be done without shims, and it's really not that hard. The use of a 30hz test tone is usually more than enough to help center things without removing the dust cap. When removing the dust cap and gluing it on again afterward, it is very hard to get it looking perfect again. Even in the case of people who have been doing it for decades and who do a very good job, the glue still generally does not look the same and it's immediately noticeable that the dust cap has been removed. I generally feel that the very very tiny chance that there might be some voice coil rubbing is worth having the cone look practically brand new afterward without ever having to touch the dust cap or the dust cap glue. It's a lot easier also! You should be able to tell pretty quick anyway, via the 30hz test tone, if there is any rubbing. Having done it this way many times now, I've never had the voice coil rub even once.

SEAWOLF97
05-30-2016, 07:16 PM
I shimmed on the first one ever . Was told that it's absolutely necessary. :barf:

Then started to do it by feel. While the glue is setting , just work it in/out on the X, then Y axis. When happy, then secure the ring down. In most likely over 100 refoams, everyone has come out perfect using that method.

Tweak48
05-30-2016, 09:10 PM
Thanks for the tips. I think I'll give it a shot centering it by touch. I've done 4 Tannoys and 2 Infinitys and never had a problem.


When removing the dust cap and gluing it on again afterward, it is very hard to get it looking perfect again. Even in the case of people who have been doing it for decades and who do a very good job, the glue still generally does not look the same and it's immediately noticeable that the dust cap has been removed.

I think you're right about that.

I'll report back.

svollmer
05-31-2016, 04:51 AM
Thanks for the tips. I think I'll give it a shot centering it by touch. I've done 4 Tannoys and 2 Infinitys and never had a problem.



I think you're right about that.

I'll report back.


I have extra CD's with 30Hz test tones if you need one. PM me if you want one and I'll mail you one.