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View Full Version : Aging JBL 4411's and Foam



groover
12-14-2008, 01:18 PM
I have two pair of JBL 4411's that are the same age and have been in the same environment all their lives. Two of them have rotted foams around the driver and two do not.

I am planning to repair the foams on the two with repair kits. The question is: Are the other two fine if they haven't rotted yet, or are they just days away?

Is rotting foam an either it is or it isn't or are there degrees of rot and then at some point it becomes visible.

If the others are right behind, I might as well repair them now rather than do two today and two more next month or next year?

Thoughts for a newbie?

Rolf
12-14-2008, 01:34 PM
Hi. Welcome to the forum.

Re-cone all is my advice. (If available) If not, re-foam is the alternative.

mech986
12-14-2008, 01:38 PM
Hi Groover,

Welcome to LH!

If you have good experience in doing the surrounds, have the correct surrounds, and placing them on the back of the cone like OEM, then you probably should do all 4.

If they are the same age, at least over 10 years old, then the intact surrounds are probably on their last legs. If you play some serious music at any significant volume, they will likely begin to fail.

So better safe than sorry, do all 4 at the same time and you'll have knowledge and security that they'll be ready to rock for another decade at least!

The more interesting question is whether you might consider doing some refurb work to the crossovers - replacing caps for newer polypropylene caps, improving the bypass caps, or consider charge-coupled biased caps on at least 1 pair to see what improvements you could wring out of them.

Others will come in with comments too. Good Luck with your resurround project. Snap some pics of what you've got and show us the progress on your woofers.

Regards,

Bart

SMKSoundPro
12-14-2008, 01:39 PM
First off, welcome to the forum! There are many good people here and they all carry varying experience of JBL products. Stick around and read some of the posts.

I also have a pair of 4411's that I received from a friend that were pretty trashed. I have refoamed the woofs and from all of the information I have read here that they are very worthy bookshelf speakers.

My 25 year experience is to recone speaker drivers in matched pairs. So, I also refoamed the 128h woofers at the same time. On the first 128, I cut of the dome and put centering shims down into the gap to make sure all was centered and to hold the spider level, as it had sagged a bit. On the second 128, I used MEK to melt the glue holding the spider to the basket and removed the cone, entirely. This gave me a chance to clean out the gap with masking tape diggers and compressed shop air. There was quite a bit of crap in the gap, akin to these speakers being in someone's workshop above the bench grinder.

All worked out well and now they are sitting here waiting to be re-installed and start singing again.

The short answer is: Yes. If at all practical, recone or refoam or rediaphragm speaker drivers in pairs. You will be amazed at the end results!

Scotty.

BMWCCA
12-14-2008, 08:41 PM
Personally, I'd re-foam the bad pair and then compare them to the ones with original good surrounds. It's a nice opportunity to compare. Of course it's a safe bet you'll end up needing new surrounds on the other pair sooner or later, but if they're not crumbling, then let 'em sing.

groover
12-14-2008, 08:42 PM
Ok, so knowing I'm very handy and somewhat technical, but have never re-foamed a speaker before... is this a project for me at home, or is it something I should leave to a pro for fear of making things worse?

If I do it, I presume there are varying qualities on repair parts. Where should I look for the best kits?

Also what's the difference between re-foaming and re-coning?
What about just buying all new woofers for the case?

And my next post is about a pair of 4311B's :)

Rolf
12-15-2008, 01:29 AM
Also what's the difference between re-foaming and re-coning?


Re-foam = you only change the foam (the rotten ones)

Re-cone = you replace the entire cone, including the spider and the voice coil.

BMWCCA
12-15-2008, 05:55 AM
Re-foam = you only change the foam (the rotten ones)

Re-cone = you replace the entire cone, including the spider and the voice coil.The first can be done DIY, the latter should usually (always!) be left to a pro since that's how the proper kits are sold. The former is quite inexpensive, the latter might cost as much as your speaker pair is worth. There's a great re-foam/re-edge thread on this site. For my surrounds I used Rick Cobb since I wasn't interested in cutting out the dust caps. You can find him here:


email him: Rick Cobb (rcobb@tampabay.rr.com)
check him out on Ebay: http://myworld.ebay.com/looneytune2001/
To see a detailed step-by-step do determine if you want to tackle a re-edge job yourself, see Bo's excellent thread here: http://audioheritage.csdco.com/vbulletin/showthread.php?t=469

Rolf
12-15-2008, 10:11 AM
I agree. Just took the "short version".:o:


The first can be done DIY, the latter should usually (always!) be left to a pro since that's how the proper kits are sold. The former is quite inexpensive, the latter might cost as much as your speaker pair is worth. There's a great re-foam/re-edge thread on this site. For my surrounds I used Rick Cobb since I wasn't interested in cutting out the dust caps. You can find him here:

To see a detailed step-by-step do determine if you want to tackle a re-edge job yourself, see Bo's excellent thread here: http://audioheritage.csdco.com/vbulletin/showthread.php?t=469

robertbartsch
12-15-2008, 02:18 PM
...not sure if it is clear from the responses above but JBL does not sell kits for the replacement of the foam surrounds only. Only aftermarket companies (non-JBL suppliers) sell these foam surround replacements.

If the authentic JBL parts are available for your vintage drivers, these would be sold to a dealer/technition in kit form only. JBL driver kits include a cone, spider, surround, voice coil and the cap. These should be installed by a JBL tech only. Authentic JBL driver kits are NOT sold to the general public - for a good reason.

Welcome and good luck!

evans224
12-16-2008, 11:19 PM
Refoaming is not difficult, but can be time consuming. I just did these from L100T's. Welcome, and heed the good advice here. Run a search first, and chances are you will find what you're looking for.

groover
12-23-2008, 04:18 PM
Mech986,

How would I go about testing the crossovers to see if they require any work? Is there any tell tale from the sound once I hook them up? I don't have them in my possession yet for photos, sound, etc. Will get them in a couple of weeks.

I do have the 4311b's hooked up and they sound wonderful. Anything crossover wise I should be checking on them as well?