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jmpsmash
09-24-2019, 04:20 PM
I recently acquired a pair of 2441. On one of the drivers there is a noticable distortion sound at a certain high frequency. It almost sound like clipping or something rattle inside. It is only on one side and I have tried switching L/R on the amps and it is not the amp or source.

I am wondering how I should go about fixing it?

engineerjoe
09-24-2019, 04:29 PM
To the best of my knowledge, the diaphragms are installed snug, then they can be slid slightly to center them in the gap. It's connected to a tone generator and run up thru the freq. to check for rubbing.
Unless there's actually something else in the gap, like metal filings, the diaphragm just might need centering?
Because they are used, the diaphragm needs to come out and inspected. It could be partially burned or similar causing this.
If the magnet structure is loose, that's beyond my pay grade. Possible dropped or smashed?
I am not a JBL tech and only guessing this stuff from my past experiences. Wait for the pros!

Mr. Widget
09-24-2019, 05:19 PM
I recently acquired a pair of 2441. On one of the drivers there is a noticable distortion sound at a certain high frequency. It almost sound like clipping or something rattle inside. It is only on one side and I have tried switching L/R on the amps and it is not the amp or source.

I am wondering how I should go about fixing it?
If you are lucky it is a dirty voice coil gap. Look up gap cleaning... there are numerous posts on this forum. It is also possible that the diaphragm simply needs to be properly centered as suggested above, but it is also very likely that you have a damaged diaphragm. (Possibly two damaged diaphragms.) :banghead:

I'd recommend sending both drivers to a qualified repair shop. Simply opening these up is dangerous since the strong magnetic pull can grab your screwdriver and cause you to puncture the precious diaphragm.


Good Luck!


Widget

jmpsmash
09-25-2019, 11:03 AM
Thanks all for the advise. I will open it up and inspect it tonight. Will try to take some photos.

jmpsmash
09-29-2019, 01:41 PM
I managed to open up the 2441 and played around with it. there are signs of stains on the metal body as well as there are marks on the diaphragm itself. I did my best to clean up all dust and particles I could find with IPA and also did the card/tape method to clean up the gap. I didn't manage to pick up much more than dust particles.

it is quite nerve wrecking but incredible to see such a thin layer of metal can produce such clear sound in such volume.

anyhow, putting it back was also challenging, I played piano music while listening to the sound. The same piece of music used to produce so much distortion due to the amount of harmonics from the piano. I managed to nudge the diaphragm frame to a point where I cannot hear any distortion and it worked! Now I don't hear it anymore.

However, I also notice that the foam lining the driver cover is badly disintegrating. Just touching it causes pieces to fall off. What can I do about that?

Earl K
09-29-2019, 02:14 PM
Take the crumbling foam out of the back cap and replace it with some 3/8"-1/2" thick felt ( made from felt liners for winter boots or felt insoles, etc. ) .

:)

jmpsmash
09-29-2019, 04:39 PM
Take the crumbling foam out of the back cap and replace it with some 3/8"-1/2" thick felt ( made from felt liners for winter boots or felt insoles, etc. ) .

:)

At least that's easier to find than a genuine JBL 2441 diaphragm!

jmpsmash
09-29-2019, 04:42 PM
Here are a couple of photos:

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engineerjoe
09-29-2019, 06:05 PM
from here the best that I can tell, the gap looks bad. It maybe locking up the diaphragm causing that distortion.
Oops! missed your post that it's already cleaned up. This is the before picture?

jmpsmash
09-29-2019, 10:55 PM
Apologies for the poor quality photo. It was challenging to take a clear photo with the phone camera. Here might be a clearer photo, not the best of condition as there are some stains inside the gap. However, the gap is clear and I managed to fit a thick namecard with sticky tape but only managed to pick up dust and no metal filings.

I also pick up some debris on the throat side stuck around the mesh.

I spent a couple hours listening to it tonight and the sound is clear! Plan is to just keep it and I am just using it for home listening and nothing too harsh, hopefully it will last.

Now I need to figure out what to put on top of it. I ordered a pair of Fostex T925A which should arrive in a couple of days but a pair of really new looking 2405 popped up on CL. Should I go through having to deal with used drivers again or have the peace of mind of buying new? Decisions!

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