PDA

View Full Version : Realigning the pole piece



boputnam
09-23-2006, 05:00 PM
OK, doods, here's a heartbreaker...

Beauty vintage driver, just reconed arrived ruined during shipping by FedEx. FedEx is honoring the claim in full, but the damage is done.

The motor popped off the basket and jumped out of position. The vc was not damaged, but it matters not. Things are not right. The bostik glueing the motor to the plate had dried-out and become brittle - it could not stand the physical shock. THIS IS THE BIGGEST RISK WITH SHIPPING VINTAGE DRIVERS.

I struggled with how to get the motor off the basket and devised the boimechanics pictured. Plywood on my chest, wooden pole, wooden cup over the vent and a two-arm pull. Easy as pie.

Now, is there any way to realign the pole piece in the plate? On resetting, the basket/plate want to rest against the pole piece. Very strong magnetic flux right there (by design). The entire motor is held in-place by bostik - no algnment holes, no nothing but the gap.

Has any one done this successfully, or know a shop that does? JBL Pro will not... :(

boputnam
09-23-2006, 05:01 PM
...

Zilch
09-23-2006, 05:26 PM
Has any one done this successfully, or know a shop that does? JBL Pro will not... :(Sure, Audivex, assuming the break was clean at the glue line and the magnet not fractured.

It's time you came over here for a visit, anyway.... :thmbsup:

boputnam
09-23-2006, 05:37 PM
Wow - thanks, Zich! There is no break - just the bostik let go of the plate. No fracture to the magnet.

You're right - overdue for that... Festival season is soon coming to an end - that will free-up a lot of the lost weekends...

Ken Pachkowsky
09-23-2006, 05:46 PM
There is a nice looking pair of what are becoming very hard to find drivers. Hope you can save it Bo.

Ken

Guido
09-23-2006, 06:04 PM
This recone is perfect!!! I can guess who did it.

Save this speaker Bo! Good Luck...

boputnam
09-23-2006, 06:14 PM
This recone is perfect!!! I can guess who did it.:yes: An artform unto itself...

Ian Mackenzie
09-23-2006, 06:28 PM
Bo,

Had you thought about using a shim like in recone kit.

I have a 2122 recone kit and I just looked at the shim, it would not be strong enough. You might be able to get one machined out of brass or aluminium. But perhaps it would be better to find a good fitter and turner. This is what they are trained for.

Ian

Thom
09-23-2006, 06:36 PM
God I love alnico. I dropped a D130 and knocked it slightly out of alighnment. Recone would have cost more than what I payed at the swap meet. I determined which way the magnet had to move, smacked it with a 2x4 twice, good as new. Now as to your problem, I didn't even know they glued together. I had the rivets loose on an LE5, bought it that way so I don't know how it happned but were talking real loose, removed them with a dremol and replaced them with brass cap screws, but if this happened shipping than anyone who cones for a touring band must have seen it, so I'd look for someone who cones for touring groups. My experience has always been that if they are on jbl pro's list they probably won't admit to doing anything the factory doesn't do. There is a guy in sacto, His father started a shop there over 50 years ago. Don't know if he currently has a shop or is working from his garage. but if there is a way to do it he probably knows it. I'm not trying to say "he's the greatest". There are probably good people closer, but if you strike out his name is Ron Neil and if he currently has a shop it's probably called neils speakers. If this happened to yours while packaged fairly well, touring speakers shipped mounted must get more stress than that. It would seam that it would be as simple as the right glue and the right fixture. Have you seen this before? I think there are a couple of speakers on ebay like that right now.

boputnam
09-23-2006, 07:00 PM
Had you thought about using a shim like in recone kit. ... I have a 2122 recone kit and I just looked at the shim, it would not be strong enough. I did, but I agree. Plus, the shim is slightly thinner than the gap. This job needs a spacer ring at the gap size.

I think I now know why so many drivers have the same diameter voice coil - I need that spacing ring, dammit...

Ian Mackenzie
09-23-2006, 07:06 PM
Yep, thats a given my friend.

A shop would be able to spin one off for you. The amazing Widget ..he may know someone.

Ian

subwoof
09-23-2006, 08:36 PM
You think that JBL would of invested in a few screws to keep them together????

Nah - an extra 40 cents. The original gray ferrites actually did. BUT the screws would bend anyway from the heavy weight because they were non-magnetic softies.

Anyways that magnet is the same one as the 2214 ( they did reuse them all over the place ) - I happen to have one sitting in the shop with a cracked frame from the same "boys in brown" treatment

Forget the blood blisters - send me an address and it's yours.

I have sent a number of them to be re-cemented and NO it cannot be done with any amount of accuracy unless the ferrite is demagg'ed and even then I still had only a 75% success rate.

Overall not worth the expense.

sub

boputnam
09-24-2006, 11:42 AM
Hey, sub!! Haven't talked to you in over a year!

Lemme first see what this dood in the East Bay can do - I think this can be restored. Thanks for the really generous offer.

Robh3606
09-24-2006, 12:35 PM
Hello Bo

That stinks!!! I just went through this with a 2435 and it was difficult to do. You need shims made up that are about .001/.002 less that the gap. If you try to go dead on it will jam. You need some play to be able to position them. Figure one of them you will have to pull out with pliers so make sure you have a pull whole in it and you lubricate them as well. If I were you I would take Sub up on that frame.

Rob:)

subwoof
09-24-2006, 05:24 PM
I noticed you cut out the spider.

:(

Since this was a recent recone, a liberal dosage of MEK would of softened the glue and you can then seperate it with a well worn small flat blade screwdriver ( #1 ) . Knife blades are somewhat risky.

If you then unsoldered the leads, you could of saved the kit ( sans foam of course).

One trick is to use a stanley 3/4 wood chisel ( their steel is the best ) and seperate the mag from the piece that shifted with some love taps from a nearby hammer.

Now get a handful of pig stickers ( massive flat blade screwdrivers ) to act as levers, shims and finger protectors.

Then use a sucession wood shims until you can lift away.

At this point you can stop and you will have a PERFECT passive radiator.

At 190.00 for a recone, it's worth the risk. Done this many times and usually the cone survives.

sub

PS- the 128H mag is the same too.

boputnam
09-24-2006, 08:10 PM
Yea, I did. Radical surgery. There was no way to tell the vc wasn't damaged. The cone was frozen, so I assumed the vc was wrenched in the misaligned motor. Wrong. The magnet and pole piece had jumped out far enough that the shallow vc was left just sitting there, pristine. Bummer on top of bummer. You cannot imagine the terrible feeling of cutting away a perfect Giskard recone. A truly beautiful job. It was an awful feeling. Anyway...

The E110 is identical, as is the gap. Hoping that can be an alternative, too.

Thanks for all the input. I feel like I can see the shore again... :smthsail:

Thom
09-25-2006, 10:16 AM
I talked to Ron Neal at Neal's Speaker Service he said he can align and glue the magnet and pole piece for $40.00 plus the recone and he would have had to tear the cone out anyway. (916) 363-6524 www.nealspeakerrepair.com

GordonW
09-29-2006, 10:46 AM
I've reglued many of these, too. About a 95% success rate. Occasionally, one will wind up being off in alignment... but the vast majority are recoverable.

What it takes, is some REALLY THICK shims, of the type used to re-cone Eminence Omega series pro woofers. Stack a couple of these shims together, and fill in to proper fit with thinner shims between the Omega shims. We've even got a chart somewhere at the shop, listing how many Omega shims and what other shims are required for specific woofers...

Regards,
Gordon.

Thom
10-12-2006, 09:17 PM
http://recone.com/magnet.htm just ran across thiss

audition
10-13-2006, 01:02 AM
O.C.S.R. does it all, including Speaker Magnet Realignment

boputnam
10-13-2006, 01:46 PM
Just to close out this rather dramatic chapter in my JBL experience...

The repairs were expertly done by:

Audivex Loudspeaker Service
1345-A Martin Luther King Blvd
Berkeley, CA 94709
(510) 527-1391

On recommendation of Zilch and Widget I chose to try Audivex. With the rarity of these 2122H's, I wanted to stay local so I could pick-up the repaired driver. I did not want to risk shipping these (ever again... :( ) unneccessarily.

Audivex was prompt and very reasonable. Thanks to Daniel, my 4345's are back in full service. Nice... :dancin:

edgewound
10-13-2006, 03:15 PM
Looks like they do nice work.:applaud:

boputnam
10-13-2006, 07:50 PM
Looks like they do nice work.:applaud:Yea, edge. Coming from a pro 'coner like yourself, that's mighty generous.

I complimented him particularly on the glue line - I know you guys take pride in getting that right.

Guido
10-14-2006, 03:15 AM
I complimented him particularly on the glue line - I know you guys take pride in getting that right.

Yeah, but this one is not 100% handmade ;) Seems to be some turntable and glue gun involved.

I still work with the pure glue tube but am close to this during the years :p

Zilch
10-14-2006, 01:24 PM
I don't know how he does it, but I've posted pics of his dome-setting here before (2235H recone, top). Proprietary, no doubt. ;)

From their original condition, I'd have thought these 116H-1s (bottom, for Minis,) would never play again. :(

Not so, obviously.... :)

127As (rear) are in process.

[For my recent closed-box affliction. :p ]

Point being that even the worst of flea-market/garage-sale vintage JBL drivers can often be nicely restored.... :thmbsup:

John
10-14-2006, 01:40 PM
I hope he used the right spider?

Zilch
10-14-2006, 01:51 PM
I hope he used the right spider?I'd put money on them being "Right," yes.... :D

Well, I'm glad it worked out for Bo, and also that I could help make it happen, even in a small way.... :yes:

edgewound
10-14-2006, 02:36 PM
... Seems to be some turntable and glue gun involved.



That's a factory trained procedure.

Guido
10-14-2006, 05:11 PM
That's a factory trained procedure.

We do not have the factory over here ;)

boputnam
10-14-2006, 07:09 PM
I'd put money on them being "Right," yes.... :DAbsolutely.

Daniel (Audivex) uses only OEM kits, as does our edgewound - these pros know what's best for our drivers. The JBL kits come with the spider pre-attached to the assembly. Their great handiwork is why we keep going to them!

Zilch - thanks for the referral. I look forward to that "afternoon in the Zilch lab". Very soon!

John
10-14-2006, 07:18 PM
Ok!!! I thought you were hoping to try and save the Giskard installed kit? I bet you wish'd you had known about the local guru before this
mis-adventure:(

Mr. Widget
10-15-2006, 01:00 AM
Ok!!! I thought you were hoping to try and save the Giskard installed kit? I bet you wish'd you had known about the local guru before this
mis-adventure:(Daniel is a very nice fellow who does really good work... that said, the work he has done for me really doesn't compare to the work I have seen from the G man.


Widget

jbl
10-20-2006, 10:52 AM
Are all JBL woofers glued? Not too thrilled about that.

Ron

gerard
05-03-2007, 04:59 AM
Hello

I am repairing a shifted magnet on a 2118 .
I already open and dismount the magnet and need to reglue it when centered .
Does someone can recommand some glue . ( and Do I have some chance to succeed ? )

Best regards

Gerard

GordonW
05-03-2007, 08:52 AM
Hello

I am repairing a shifted magnet on a 2118 .
I already open and dismount the magnet and need to reglue it when centered .
Does someone can recommand some glue . ( and Do I have some chance to succeed ? )

Best regards

Gerard

"30 minute" 2-part epoxy is my glue of choice, on these. The 5-minute stuff is also usable, but not quite as strong.

Stuff like JB Weld or long-cure-time epoxy can work, but IME, it oftentimes dries too 'brittle', resulting in the possibility of the glue cracking and re-breaking in the future. The tiny amount of elasticity in the 30 minute epoxy seems to be about optimal, IME.

BTW: DO NOT use superglue on these. Too brittle, and not enough affinity for the ceramic magnet material. A glue joint on a magnet made with superglue likely WILL fail again.

Regards,
Gordon.

gerard
05-03-2007, 09:34 AM
Thank you Gordon .

Could I know also what is the tolerance I can have for centering ?

1 mm 2 mm ? and what can happen if it is not perfectly centered ?

Regards

Gerard

edgewound
05-03-2007, 10:44 AM
[quote=GordonW;166594BTW: DO NOT use superglue on these. Too brittle, and not enough affinity for the ceramic magnet material. A glue joint on a magnet made with superglue likely WILL fail again.

Regards,
Gordon.[/quote]

Well...I'll respectfully disagree with that blanket statement.

Super glue...AKA cyanoacrylate...comes in many different formulations.

The key is to find a high impact, elastomer modified industrial strength cyanoacrylate to do the job.

Look at Henkel's (Loctite) CA glues.

The biggest variable problem with two part epoxy is getting the mix perfect. Cyanoacrylate is perfect right out of the bottle.

edgewound
05-03-2007, 10:46 AM
Thank you Gordon .

Could I know also what is the tolerance I can have for centering ?

1 mm 2 mm ? and what can happen if it is not perfectly centered ?

Regards

Gerard

Gerard....you need to get it accurate within +/- .002".

If not....you'll risk a wasted effort and voice coil rub.

SMKSoundPro
05-03-2007, 01:37 PM
I have 2- 2402 ferrite motors in the same shape. I would like to glue them back together as I dislike numerous JBL paperweights.

I have some brass rail stock left over from the bar's footrail that is a touch too large in diameter (1-3/4" I believe), and a very close thickness match to that of the gap, and with relief cut along its length of a 4" piece, am hoping to use 30 minute epoxy, and slide the top plate back on, using the 6-32 mounting screw holes with long threaded screws installed, to act as a reverse jacking screw. Gently unscrewing the four until to plate rests in the epoxy, then clamping with gentle pressure to keep the epoxy out of the places where it should not go.

Does this sound like a reasonable method of repair?

Scott.

edgewound
05-03-2007, 01:51 PM
I have 2- 2402 ferrite motors in the same shape. I would like to glue them back together as I dislike numerous JBL paperweights.

I have some brass rail stock left over from the bar's footrail that is a touch too large in diameter (1-3/4" I believe), and a very close thickness match to that of the gap, and with relief cut along its length of a 4" piece, am hoping to use 30 minute epoxy, and slide the top plate back on, using the 6-32 mounting screw holes with long threaded screws installed, to act as a reverse jacking screw. Gently unscrewing the four until to plate rests in the epoxy, then clamping with gentle pressure to keep the epoxy out of the places where it should not go.

Does this sound like a reasonable method of repair?

Scott.

Make sure your gap is .025" and don't use too much epoxy, or you'll impede the gap with goo.....which would be bad.

SMKSoundPro
05-03-2007, 02:13 PM
Make sure your gap is .025" and don't use too much epoxy, or you'll impede the gap with goo.....which would be bad.
Thank You!!!

subwoof
05-03-2007, 04:19 PM
We will we will DROP you...

sing it!

:cheers:

subwoof
05-03-2007, 04:21 PM
Here is a 2225 magnet obtained from a heritage member a long time ago - apparently the magnet was reglued "at home" and it is *just* enough off center to make it useless...

So if you use shims, make sure it is CENTERED.

SUB

GordonW
05-04-2007, 08:30 AM
To reiterate the last few statements... if you shim a magnet for reglueing, MAKE SURE YOU SHIM IT TIGHT.

And believe me, I practice what I preach. I've shimmed magnet reglues SO TIGHT that other folks in the shop SWORE that they couldn't ever get the shim back out. Most of the time, they hand the things right back to me, and MAKE ME "get the $*&% shim out of the %*&^". I've always managed to extract the shims (sometimes takes more time than others)... and as a result of the shims I use, I've NEVER had an off-center gap.

Sometimes it takes experimentation with different thickness plastic shim stock... I've used combinations of report cover plastic, photo film stock, and other materials, to make up the proper thickness to TIGHTLY hold the gap in place. It's more work, but it's the ONLY way to do it RIGHT, IME...

And as for superglue- unless you have access to specialized polymerized industrial grade CA adhesives, you're MUCH BETTER OFF using epoxy than "store-grade" superglue. I speak from numerous experiences here. Among the concerns I voiced earlier, you ALSO get the opportunity to ADJUST or RE-DISASSEMBLE the glue joint, should something go wrong. Most cases, with CA/superglues, once the magnet "grabs" the pieces together, you're done... no way to get the parts apart again. No margin for error, which is NOT a situation I would espouse for someone who's NOT done it before, MANY TIMES...

Regards,
Gordon.