misaligned gap in 2440

[franz]

Hi everybody!

I have a single 2440 driver which has a misaligned /excentric gap.
Gap width is about 0,8 mm on one side and almost double of that on the opposite.
This is just a guesstimate since I have no suitable gauge at hand.
Anyway, a new diaphragm will probably not fit in.

What can be done in such a case?
Is there any remedy that can be done outside the JBL factory?
Shipping back and forth will become too costly.
How is the polepiece fastened within the gap?

Anybody ever had the same problem?
Thank you guys for any help!

Franz

[Maron Horonzakz]

The unit will have to be demagnetized . aligned . and remagnetized. Your driver must have been bumped hard or dropped to be missaligned.

[scott fitlin]

Send that driver to JBL, its a job only they should do! It will have to be demagnetized, then taken apart to realign and center the gap, then put back together, and remagnetized!

[Alex Lancaster]

I have never had to recenter a compression driver, but some speakers by the rubber mallet method, would that work here?, it might save a bunch of bucks.

[Maron Horonzakz]

A good kick with a steel toed boot might do it. At the moment it,s only good as a door stop.

[paragon]

Hallo Franz,

Never heared this. Ask audiopro in Heilbronn.
www.auidiopro.de
Maybe they can help.

Regards
Eckhard

[paragon]

Sorry,

It`s www.audio-pro.de !!

[Mr. Widget]

The 2440 is held together only by it's magnetic force. While you could probably continue to beat up the driver and get the gap to shift a bit here and there you will need ten thousand years with ten thousand hammers to get it truly centered. BTW all that tapping will partially demagnetize your driver, so by the time you get it centered the response will suffer.

Unless you can find someone in Europe with experience centering the magnet and pole piece and has their own gauss-o-matic or whatever the machines are called, your options are not good.

Widget

[Hofmannhp]

Originally posted by Mr. Widget
The 2440 is held together only by it's magnetic force. Widget

Hi Widget,

is it right what you wrote,...I mentioned about this since some years....I think that it's possible what you wrote. Is there some very thin glue on the pole piece to fasten the position of the pole plate? BTW, is anybody here who's got a cut drawing or pic through the driver.

Last week I had success with the cleaning of two 2441 gaps, which were full of steel chips and very small steel particles. It took 4 h to clean the gaps by the use of a nonmagnetic 0.5mm brass part with double sided carpet glueing tape.

HP

[franz]

Hi Widget and others!

Thanks for all your input!
I allready guessed that demagnetisation might be necessary.
What tool does one need to center the pole piece then?

I found it interssting that there is no adhesive between the pot and the magnet. So its all loose before the magnets are energized?
What about demagnetizing. Can this be done in an oven at say 250 °C? What happens to the phase plug (looks like plastic to me) then?
Opening Pandora´s box, huh !?



Franz

[Mr. Widget]

If you bake it, it really will be only useful as a boat anchor, and not a particularly good one at that.

The phase plug and the throat are both plastic.

You need the proper equipment and expertise to do this task.

Widget

[scott fitlin]

Originally posted by franz
Hi Widget and others!

Thanks for all your input!
I allready guessed that demagnetisation might be necessary.
What tool does one need to center the pole piece then?

I found it interssting that there is no adhesive between the pot and the magnet. So its all loose before the magnets are energized?
What about demagnetizing. Can this be done in an oven at say 250 °C? What happens to the phase plug (looks like plastic to me) then?
Opening Pandora´s box, huh !?



Franz

Ship the unit to JAY-BEE-EL and all will BE WELL!

[Flodstroem]

Dear Mr Franz
Read about your misaligned 2440-magnet
I allso have one with the same problem which I must repaire soon.

I have (possible) some idea hove to solve this problem, but first I would like to get some coments from Mr Widget or Mr Giskard on the following idea:

If it was possible to move the polepiece in the gap by a controlled force and if the polepiece was realigned to the center of the gap by this force, ( but without a -"thousand hammers", Mr Widgets did comment), what result could be expected

If the polepiece then was centered, then it would be possible to make a measurement for a possible weak magnet.

This idea could possible be done with tools involving a lathe and a hydraulic pressure.

Depending on the comments I would like to write you an answer regarding the detailes of this idea.

"closer to transmission line than ever before"
Best Regards