JBL 4406 - 035ti tweeter repair question

Congrats on your repair! Oh man do I know about repairing 035TI.......
Thanks dragondad ! It was very satisfying to do the repair and it worked.


Here is something to keep in mind. The only thing holding the magnet and pole to the top plate is some old dried out adhesive. A sharp bump can easily cause the magnet to shift. If they are still properly centered you can run a bead of epoxy around between the 2 pieces to secure it.

I think these JBL 4406 "studio monitors" may be a little different than the L20T (the consumer version of these 4406) .... on these the mag is screwed to the top plate (diaphragm/coil) with 4 (allen head) screws. I guess yours didn't have these?

P1040657_cr.jpg
 
Yeah , I wasn't sure about this either. But it just falls apart when you touch it, so I just left it like it is. It looks like it would be very easy to get some of it wedged down between the voice coil & magnet! BTW, it was a chore to get that mag back on without damaging the voice coil ... It has to line up just right.

I would imagine that with the foam stuck to the driver it would severely hamper the weight and crispness and inhibit the ability for the diaphragm as it is a lot of extra mass that it is now having to move.

I'll see f I can find a old thread that talked about retro fitting a new piece of foam to the mag.
 
I'll see f I can find a old thread that talked about retro fitting a new piece of foam to the mag.

Cool, Thanks ..... Just what exactly does that foam do anyway? What would be the harm in just eliminating it?
 
Cool, Thanks ..... Just what exactly does that foam do anyway? What would be the harm in just eliminating it?

I think it help reduce sound waves bouncing off the magnet and returning to the diaphragm. But Im not 100% sure.
 
Thanks dragondad ! It was very satisfying to do the repair and it worked.




I think these JBL 4406 "studio monitors" may be a little different than the L20T (the consumer version of these 4406) .... on these the mag is screwed to the top plate (diaphragm/coil) with 4 (allen head) screws. I guess yours didn't have these?

P1040657_cr.jpg

No, the tweeters are the same. Those Allen head screws only go through the top plate and stop, they to not actually penetrate to the magnet. The only thing holding the magnet to the top plate is magnetic force and old glue. A sharp knock can shear the glue and cause the magnet to shift. When I get a chance I will take a picture of the unit I have that is completely apart
 
No, the tweeters are the same. Those Allen head screws only go through the top plate and stop, they to not actually penetrate to the magnet. The only thing holding the magnet to the top plate is magnetic force and old glue. A sharp knock can shear the glue and cause the magnet to shift. When I get a chance I will take a picture of the unit I have that is completely apart

That is different than mine. Mine , the magnet has holes that are threaded and the screws threat into the magnet. That's weird if yours are different... but I know on mine the mag is held on by the screws!
 
Yep! It is held in place by glue, nothing else keeps it centered. It looks like 1 piece until you have seen it fall apart. :no: On my repaired tweeter I ran a bead of JB weld around the joint you show with your arrows to keep it in place. It is held together by magnetic force, but centered by the glue. Once the glue fails, it shifts easily and is very difficult to center again. Pics show one together and one apart, notice the one together is not centered. Also see how the screws only go through the plate? I have one diaphragm and coil that are repairable once I center and re-glue one of these magnets. The other coil got damaged beyond repair.
 

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This is what I found when I opened my box. It took me a few minutes to figure out what happened. You can see the magnet came completely off the top plate, which is still screwed to the diaphragm flange. And yep, when it fell the pole ripped the voice coil loose from the diaphragm.

Anyway, all the effort was worth it, the L20T sound wonderful!
 

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This is what I found when I opened my box. It took me a few minutes to figure out what happened. You can see the magnet came completely off the top plate, which is still screwed to the diaphragm flange. And yep, when it fell the pole ripped the voice coil loose from the diaphragm.

Anyway, all the effort was worth it, the L20T sound wonderful!
WOW .... That sux! I really thought that was part of the mag. Now I know and I will be more careful with these knowing this. Man if that mag moves at all I'm sure it would make contact with the voice coil because there is very little clearance between the coil and the mag.

Thanks for showing the pics :thmbsp:

I am going to try to get the other one done tonight.
 
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