Odd 2225

[Allanvh5150]

Hi all,

I am cleaning up some 2225 frames ready to drop 2235 kits into them and I have noticed something odd with one of them. One speaker had a blown voice coil, half of which was still in the gap. After managing to hook all the copper out of the gap I noticed that there is a ring that looks similar to a 2235 mass ring loose inside the gap. My questions are: A, what is it? and B, how do I take it out or do I need to worry about it?

Allan.

[subwoof]

It is a ring that is supposed to be cemented to the underside of the pole piece to counter the eddy current effect in the magnetic structure.

This is described in detail on the tech paper JBL put out back in the early 80's and should be on the technical reference area of this ( and JBL's ) site.

This laptop has none of my cool JBL bookmarks and it's bedtime...

You need to reglue it back in place before reconing - that's a project in itself.

sub

[Allanvh5150]

Thanks Sub,

That is what I thought it was but i couldn't find a pic of it.

tell me how to go about it.:)

Allan.

[marcuswilson]

Allan,

It's not that common that the ring falls off. It's not an easy job to repair.
Normally one demagnetises it, dismantles the magnet assembly, glues it all back together, recones it, and remags it.
I get Axent to do it, they have a magnetiser. It's usually impossible to dismantle the magnet without demaging it first. Also if you do get it apart, it will partly demagnetise anyway, because the magnetic circuit is broken.
I'm not sure if the ring can be glued in while the magnet is assembled, but it looks very difficult to me.

Marcus

[SMKSoundPro]

Hi Allan! Here are some pics of a 2225 basket that came with busted ferrite. I sent the whole driver back to JBL service and they were unable to fix it. They said no more parts available for the ferrite, and wouldn't help at all. Jenny was nice as always, and in the end i just told them to keep it and dispose of it. I really try to fix the older stuff, but JBL was not able to help at all!

I was going to make up some 2235 baskets for fun projects. Good luck with yours!
Scotty.

[Goodwill_HiFi]

I don't get it..... these are ferrite motors. I've only heard of discharging and recharging AlNiCo, and didn't think it was even possible with ferrite.

[subwoof]

Out go the lights.

Since most of the dropped ferrites crack rather than a clean shift they become doorstops.

I have 4-5 of the exact same magnet in the shop and they will sit unless I get desperate. They failed because some one looked at them crosswise. Crap glue job at the factory - ALL are 2225J theater versions.

My magnet guys say that every once in awhile one will explode during recharge. Can you say shrapnel?

And unlike the alnico pot, there is no mechanical system to keep them apart and it's only a matter of time / heat before the glue gives way.

sub

[Allanvh5150]

So Sub,

How do you go about glueing the ring back in when the magnet assembly is in one piece?


Out go the lights.

Since most of the dropped ferrites crack rather than a clean shift they become doorstops.

I have 4-5 of the exact same magnet in the shop and they will sit unless I get desperate. They failed because some one looked at them crosswise. Crap glue job at the factory - ALL are 2225J theater versions.

My magnet guys say that every once in awhile one will explode during recharge. Can you say shrapnel?

And unlike the alnico pot, there is no mechanical system to keep them apart and it's only a matter of time / heat before the glue gives way.

sub

[marcuswilson]

Allan,

You cauld call Brian Hart at Axent 09-8271220 and ask him if he's done it. He has decades of speaker repair expertise and is a helpful man.

[Allanvh5150]

Done! Well on Monday anyway........


Allan,

You cauld call Brian Hart at Axent 09-8271220 and ask him if he's done it. He has decades of speaker repair expertise and is a helpful man.

[Allanvh5150]

The fix looks quite difficult but in reality very very simple. Fixed!:)

[subwoof]

well......what is his method??

I used a glue syringe with epoxy. Holding the mag upside down was the fun part...did you know that reading glasses have steel rims??

THWANK

[Allanvh5150]

Hi Sub,

Similar technique. Downunder, the favoured way is to use cyanoacrylate adhesive (super glue). Get a cotton bud, I think you guys call them cue tips, snip the end of the super glue aplicator tube and push the hollow shaft of the cue tip into the aplicator. Squash it flat with a pair of pliers so you can feed it through the gap and glue away. Seems to work fine.:)

[SMKSoundPro]

Outstanding! Another use for a cue tip.

[Allanvh5150]

And the weird thing is that it seems to be made perfectly for the job!:D


Outstanding! Another use for a cue tip.

[robertbartsch]

Hmmmmm...

I had a similar issue with a set of 075 tweeters I had re-maged. The cores were sent out and the vendor demagnitized and remagnitized them.

Unfortunately, during the process the rings shifted and prevented the reinstallation of the noses that have a bolt runing front-to-back. Anyway, I sent them back and they demagnitized them, aligned the rings, reinstalled the noses and remagnitized the cores.

In this case, I was told the rings were never cemented from the factory which, apparently, is not the case with your 2225's, however.....

[Allanvh5150]

True. Sometimes it seems that the factory has not used enough glue! The glue is not impervious to high temperatures so when the voice coil is overdriven it heats up the ring way more than normal and the glue fails. More glue would not have been a problem as no one ever gets to see inside unless the driver falls on the floor.:D Now I am onto my second 2225 2235 conversion in two days. Two to go.

[subwoof]

??

The 075's are alnico and are assembled differently that the ferrites ( what we are talking about ). They do not have a shorting ring.

The "ring" that shifted in your tweeters is actually the magnet donut that is under the pole piece and *it* moved if your bullet didn't install.

If the magnet was charged, it could of been re centered with a simple jig without going through all those motions.

sub