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Mannermusic
02-07-2008, 03:00 PM
Greetings all -

I have two 2213 woofers with damaged dust caps that I would like to R&R. Never did it before, can't find it on the site. How can the old caps be removed without damaging the cone - the glue is like a rock. Hair dryer? Special tool? There's gotta be an easy way, brute force and awkwardness ain't gonna cut it. T'anks! Mike Manner

hjames
02-07-2008, 04:19 PM
Pretty sure I've seen images on the site of the dustcap being cut off VERY CAREFULLY with a pointy ended xacto knife.

see - http://audioheritage.org/vbulletin/showthread.php?t=17555




Greetings all -

I have two 2213 woofers with damaged dust caps that I would like to R&R. Never did it before, can't find it on the site. How can the old caps be removed without damaging the cone - the glue is like a rock. Hair dryer? Special tool? There's gotta be an easy way, brute force and awkwardness ain't gonna cut it. T'anks! Mike Manner

Mannermusic
02-07-2008, 06:41 PM
Thanks for the feedback - that thread you found was re a tiny LE5 repair, but the method may be similar for woofers as well. I too seemed to remember a picture with an exacto knife . . . but never found anything. But, it looks like they cut around the paper cap above the glue bead and then glue the new cap over the old bead. I may head over to see "JBL Jeff" at Signature Audio Services - local JBL pro shop. I have an old cone I'll try first. I read a number of procedures on the site re refoaming which talked about removing the cap to insert the centering shim but never a mention how they managed to get it off. Maybe someone will come along with info on the larger cones - might be easier . . . or something. This is a situation where experience is the difference between ruining the speaker. Patience.:blink: Thanks again. Mike

Mannermusic
02-07-2008, 08:47 PM
Thanks for the feedback - that thread you found was re a tiny LE5 repair, but the method may be similar for woofers as well. I too seemed to remember a picture with an exacto knife . . . but never found anything. But, it looks like they cut around the paper cap above the glue bead and then glue the new cap over the old bead. I may head over to see "JBL Jeff" at Signature Audio Services - local JBL pro shop. I have an old cone I'll try first. I read a number of procedures on the site re refoaming which talked about removing the cap to insert the centering shim but never a mention how they managed to get it off. Maybe someone will come along with info on the larger cones - might be easier . . . or something. This is a situation where experience is the difference between ruining the speaker. Patience.:blink: Thanks again. Mike

OK, the old cone practice answered all my questions. Yes, you need a sharp cutting tool such as exacto knife and a steady hand. It is extremely precarious because you can damage the coil assembly if you go just a bit too deep or get the angle wrong. First-timers should practice on an old junk cone - mandatory. I wouldn't try this on a valuable, difficult to find speaker. Go to the pro. Experience is key. Mike

3dbdown
04-30-2008, 02:52 PM
You can also take an acid brush and brush the glue bead with acetone. Then, when the glue softens, you can take a pair of tweezers and gently lift the dome away from the speaker cone. Works great. JBL did it that way on the production line when necessary.

Rick

Woofer
05-01-2008, 08:23 AM
.......I read a number of procedures on the site re refoaming which talked about removing the cap to insert the centering shim but never a mention how they managed to get it off. Maybe someone will come along with info on the larger cones - might be easier . . . or something. This is a situation where experience is the difference between ruining the speaker. Patience.:blink: Thanks again. Mike

It isn't always necessary to remove the dustcap when re-doing the surrounds.
I 've got quite good at simply removing the old surround, gluing the new surround to the cone, then run a signal generator with a very low frequency, eg 20 Hz and while gluing the surround to the frame, manipulate it 'till there are no rubs or buzzes, while slowly increasing the volume of the generator.
Let it set for a couple of minutes, so it has adhered correctly, but still moveable if you have to, and run the test again, but again at a slightly higher level, then gradually turn the generator down to around 10Hz. All should be well.
Allow to set over night, and test again. :)
100% success rate so far and I've lost count how many I've done. :bouncy:

Mannermusic
05-01-2008, 08:15 PM
You can also take an acid brush and brush the glue bead with acetone. Then, when the glue softens, you can take a pair of tweezers and gently lift the dome away from the speaker cone. Works great. JBL did it that way on the production line when necessary.

Rick

Ah hah! I knew there had to be a better way. Appreciate! I bought a couple old drivers with damaged caps and managed to get them replaced via careful exacto knife use, but the acetone trick would make 'em like new - less weight as well (F=MA). Thanks again. :) Mike

SMKSoundPro
05-01-2008, 10:25 PM
Acetone will also melt away the aquaplas! careful!

Mannermusic
05-02-2008, 05:34 AM
Acetone will also melt away the aquaplas! careful!

Appreciate the feedback - I was thinking about the acetone overnight (got light-headed:blink:). These old (junk?) speakers are like dealing with someone on their deathbed. When the glue is relatively new, the acetone will probably soften things relatively easily. But with 25 year old speakers, the glue is hard as a rock . . . so the process is going to take longer and the chances of the acetone creeping into the acquaplus is pretty high (unavoidable?), it would seem. No easy answers. Another thing I have noticed is that it appears gluing a new cap on top of the old cone remnant seems to change the sound character of the speaker - kind of deadens it. This makes good sense because that ring of old cone paper and glue is right at the intersection of the coil and cone where the physics would seem most critical (I compared the repaired speaker to a freshly reconed one by JBL pro shop). Acts as a damper of sorts, I would guess. Not good, in any case. So, we add old, repaired transducers to similar electronics and you have a never ending negative feed-back loop. In the engineering lab, we would have thrown the whole kit and kabootle in the scrap gondola and installed new everything. On the other hand, makes good entertainment for engineering retirees! Mike

Woofer
05-02-2008, 06:31 AM
If you can ever get your hands on an old Dentist's Drill, or Engraver's Drill setup, with the various bits and attachments, you'd be amazed at how handy these things are at doing stuff like removing dustcaps to the point, that you'd never know there was one there in the first place. Just takes a bit of practice.
I tried once with a Dremel (?) Tool, but it was just too bulky for the fine work needed.
Just my 2 bob's worth.

Mannermusic
05-02-2008, 08:06 AM
If you can ever get your hands on an old Dentist's Drill, or Engraver's Drill setup, with the various bits and attachments, you'd be amazed at how handy these things are at doing stuff like removing dustcaps to the point, that you'd never know there was one there in the first place. Just takes a bit of practice.
I tried once with a Dremel (?) Tool, but it was just too bulky for the fine work needed.
Just my 2 bob's worth.

Excellent! A lot of "trade secrets" here. Appreciate. Mike

edgewound
05-02-2008, 01:14 PM
You can also take an acid brush and brush the glue bead with acetone. Then, when the glue softens, you can take a pair of tweezers and gently lift the dome away from the speaker cone. Works great. JBL did it that way on the production line when necessary.

Rick

It might be that easy when the old Bostik glue on the production line was still soft....actually MEK was used...

It takes alot...I mean ALOT of acetone to soften that glue bead that's been curing for the last 30 or so years...and then it's not so easy to just gently lift the dome off with tweezers, unless the glue is a couple of days old or less.

You need to use a heat gun to soften the glue more after pre-treating with acetone. It takes some time and patience to get it right and you gotsta be sure you don't burn the cone with the heat gun.

I learned these tricks from the legendary late Terry Duran, the chief Service Agency Trainer, who trained me in 1988 at the factory. God rest your soul, Terry.

The procuction line has used black cyanoacrylate on the dust domes for the last two decades to speed up production time to QA test.

It's best to leave the dome in place if the coil isn't damaged. If the dome is dented and needs to be replaced, cut around the base of the dome where it meets the top of the voice coil former....with a brand new exacto knife... and then remove the remainder of the domes lip with a heat gun and precision needle nose pliers to get a good grip on it.

Go slow...patiently.

3dbdown
05-02-2008, 04:45 PM
Edgewound.

Roger on the MEK....my mistake, although I have used a wipe with acetone(carefully) from time to time to rejuvenate the appearance of my LE5 cones.

The times I've had my woofers re-done, I just had them re-coned, and never just re-surrounded. But, it's been 15 years since the last go around....I'm not even sure what re-cone kits are still available from JBL. And, truth be told, I was extremely fortunate in being able to have JBL do it for me...guess I'm a bit spoiled!

I wonder what I'll find when it becomes necessary to redo my 126A's ??

Thoughts??

Rick

3dbdown
06-16-2008, 07:54 PM
Well, I did it!! Had the 126A's reconed by Stephan in Hollywood, for an arm and a leg, of course!!

He tells me they were the last true JBL C8R126A cone kits left on the Planet....and he charged accordingly!!

Interesting, though.....the original voice coils, back in 1975, were hand-wound for me as a personal favor by Ed May, in the transducer lab....with les than 1/2db measured difference between them. When I had to replace them, in 1981, I was really bummed out about it, although the new ones performed flawlessly for the next 25 years......

Kind of a cool "full circle" for the 126A's though, if you ask me!

Luv My Jubals,

Rick

BJL
06-17-2008, 12:50 PM
I have used a wipe with acetone(carefully) from time to time to rejuvenate the appearance of my LE5 cones.
Very interesting . . . I've got an LE5-6 with a faded cone. I've speculated a previous owner might have placed it near a window with the grille removed. Looks more gray than black now. Would acetone help to darken it?

Don C
06-18-2008, 07:23 AM
No.