Is it possible to save a bad refoamed bass? 122A

[Fjonkalicious]

I first bought a pair of L65:s for a small sum, reconed and refoamed by expert, very nice job. Shortly after I bought another pair of L65(A) with bad foam. I am leaving the refoaming of these to an expert. This weekend I found 2 pairs of L36 Decade with bad foams, which I am going to refoam myself. Today I picked up a pair of L166A Horizon with refoamed bass drivers but one bad 066 tweeter. My idea was to put the 122A Bass drivers into the L65A:s and when I get my other 122A Bass drivers done, switch again.

Anyways, I bought them(L166A) cheap and took them home, the casing is full of scratches on the top, one midrange dust cap had small dents and so on. But when I moved the cone on one of the bass drivers I hear a scratch=bad refoaming, I don´t think the person has removed the dust cap, just done it with a 30 Hz tone or something like that. I wanted to see more, so I started to take out the bass driver finding out that 2 screws were missing and they were partly glued to the speaker. I haven´t got the element out of the box yet because the other screws doesn´t come off.

My question is: Is it possible to redo the refoam work or do I need to recone the driver or should I just give up?

Many thanks for answers!

Filip

[boputnam]

My question is: Is it possible to redo the refoam work or do I need to recone the driver or should I just give up?Filip...

If recone kits are available, that is the preferred route. Get those baskets to a qualified reconer.

If not, or if you wanna try a new surround, yourself, you certainly can. Go to the Resurround Step-by-Step and you'll find ideas, suggestions, and sources. Good luck...

[Fjonkalicious]

Filip...

If recone kits are available, that is the preferred route. Get those baskets to a qualified reconer.

If not, or if you wanna try a new surround, yourself, you certainly can. Go to the Resurround Step-by-Step and you'll find ideas, suggestions, and sources. Good luck...

Hi Boputnam,

Thanks for your quick answer. Is there any specific reason to do a recone instead of only resurround?

I spoke to the former owner which had made the refoaming by himself, he had only listened for about 5 minutes(he says without distortion, I don´t belive him).

How much is a recone kit approx USD for a 122A?

Thanks for the guide, I will read carefully!

/Filip

[boputnam]

Resurrounding is a last resort. It is preferable to use a factory kit to recone a basket and return the driver to original operating performance. But for may vintage drivers, and some others, JBL has stopped making recone kits, so we are stuck with only either a re-surround or trying a non-JBL kit.

It is hard, but not impossible, to get a re-surround properly positioned so there is no rubbing of the voice coil in the gap. I have both recones and resurrounds in my arsenal :p and remain pleased with the resurrounds, too.

Another reason to recone - this will replace the spider and surround, ensuring all are new.

One last aspect of resurrounds: There is little/no data available to us on the compliance of foam surrounds originally used by JBL. Providers of new foam surrounds have gone to great care to get the best material, but there is really no assurance the compliance is identical. Therefore, the Thiele Small parameters could be affected. Will you hear it? Dunno. If resurround is the only option, "get 'er done!"


I spoke to the former owner which had made the refoaming by himself, he had only listened for about 5 minutes(he says without distortion, I don´t belive him). I actually wouldn't doubt him. However, he is listening for rubbing, not distortion.


How much is a recone kit approx USD for a 122A? I don't see that on the current "Goes Into List" (http://www.jblproservice.com/pdf/Goes%20Into%20List/Goes%20Into%20List.pdf), but believe they are obsolete. You may be stuck. Others here will know better.

You could consider swapping in the 128-H, which I favor over the two, and is the recommended replacement...

[Robh3606]

Hello Fjonkalicious

You may be able to rescue them by taking off the old foam. It depends on how well the resurrounds are attached and what glue they used. If they are starting to peel you have be able to slowly get them off the cones without ripping them. I was able to rescue an pair of 2108's that way. Foams on the front with a lousy glue job. It's risky for sure and Bo's right recones are always the best course of action. The 122A takes the 129H recone Kit which I believe is available.

Rob:)

[Fangio]

Had such a driver on the bench recently. Actually there were four 122A's but only this one was reconed. The work was done by a JBL authorized person in Germany a few years back. I did nothing with it other than taking some pics, because it performed as it should. Got the impression the cone diameter is a tad smaller, didn't measure it though.

If your original 122A cone/spider assembly is in very good shape, I would probably try to rescue it first with a re-resurround, then go the recone route.

[Fjonkalicious]

Thanks Bo,Rob and Fangio!

Well, I will try to do another resurround again. I was worried that maybe the voice coil was damaged.

I have seen a kit from PartsExpress which includes dust cap and plastic shims, does anyone have any experience of this kit?

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=260-974

Next task is to get the driver out of the box. One of the screws just spins, another is covered in glue and the other 2 is missing.

Thanks for all the help!

Filip

[analogman]

Thanks Bo,Rob and Fangio!

Well, I will try to do another resurround again. I was worried that maybe the voice coil was damaged.

I have seen a kit from PartsExpress which includes dust cap and plastic shims, does anyone have any experience of this kit?

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=260-974

Next task is to get the driver out of the box. One of the screws just spins, another is covered in glue and the other 2 is missing.

Thanks for all the help!

Filip

Check DC resistance, check for shorts, 30K and MEK and patience accompanied by good light. Leave the dust cap alone, unless you HAVE to re-cone.

Craig

[SEAWOLF97]

Next task is to get the driver out of the box. One of the screws just spins, another is covered in glue and the other 2 is missing.

Thanks for all the help!

Filip

I had a couple of those that spun and spun...the torxnut ( ? is that what they call it ??) wasnt seated anymore...ended up putting a screwdriver blade between driver frame and cab , putting upward force against the nut and it stopped spinning long enough to remove. When reinstalling, I glued in all the nuts...no more problems.

[grumpy]

for visualization...one example/type:

http://www.woodpeck.com/tnut.html

there are quite a few variations.

The "teeth" can get bent over, or just loose in the wood (usually
resulting in chewed out "tooth holes" requiring glue to
hold them in place, or relocating the mounting hole(s) if
cosmetics aren't important.

[Zilch]

C8R129H recone kit = US$172.00 MSRP.

[Fjonkalicious]

Check DC resistance, check for shorts, 30K and MEK and patience accompanied by good light. Leave the dust cap alone, unless you HAVE to re-cone.

Craig

Finally got the driver out of the box, took me hours. Had to drill out two of the screws. I made a cut through the "old" foam and then tried to move the cone, but sometimes the scraping in the voice coil is still there.

Craig, I wonder, I wanted to take of the dust cap to center the cone from it´s scraping in the voice coil. Why should I leave it alone?

I am not a electrician by far but I tried to measure the DC resistance and my instrument says 05.8, seems this reasonable? It is not stable at first, takes some seconds to stabilize.

How do I measure the rest that you mention: shorts, 30K and MEK?

Maybe it is not possible for me to save this one, but it is good to learn.

Last question, this one 122A has white coating on the back(aquaplas do you call it??). Does this driver differ from my 122A:s from my L65A with black cone on the back?

Thanks again all of you! :)

Filip

Edit: I now cut off all the rest of the "old" foam and now the cone moves withour scraping! :-D

[macaroonie]

I have refoamed all of my bass drivers without taking out the dust cap. Remember that the coil is centered by the spider ( yellow fabric on the magnet ) but that when the surround is not there the cone can tip over with respect to the central axis. You will find that with the refoam kit once you get the foam attatched to the cone ok and then move on to the foam/frame that there is an easy adjustment to the centering. The glue has a long set time and you can reset it if need be.
Rick Cobb is the man for your foam , he will make sure you get the correct foam.
MEK = methyl ethyl keytone , good for cleaning up old adhesive.

[boputnam]

Edit: I now cut off all the rest of the "old" foam and now the cone moves withour scraping! :-DBe careful with that. Are you moving the cone by-hand? This can damage the voice coil, and lead to inevitable rubbing.

Anyway, the trick is to get the no rubbing WITH the surround glued in-place. That requires everything be properly centered.

Get someone to recone these - you'll be happiest.

[Fjonkalicious]

Be careful with that. Are you moving the cone by-hand? This can damage the voice coil, and lead to inevitable rubbing.

Anyway, the trick is to get the no rubbing WITH the surround glued in-place. That requires everything be properly centered.

Get someone to recone these - you'll be happiest.

Yes, I am moving the cone by-hand. This way I found out that they were not properly refoamed. In different stages I have been moving the cone by-hand to see if it get´s better or not. Now they seem fine and ready for a proper resurround. Well, I might aswell give it a try to do a resurround. Reconing seems is too expensive for me and for this specific speaker.