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robertbartsch
08-13-2016, 09:13 AM
Score another one for the great folks on E-bay who sell busted stuff.....

Several years ago, I purchased a pair of 2426 compression drivers from a cat in Maryland. Since I only lived a couple of hours away, I drove down and picked them up. The rubber bumper piece that protects the magnet was not seated properly, so I took it off when I got home.

I found a BAD crack in the ceramic magnet. The seller refused to take it back, however.

Anyway, I put a large hose clamp around the magnet and the driver appeared to work just fine.

Fast forward to today - about 6 years later. This speaker system, a pair with 2226, 2426 and 2405s, is now acting up. One of the pairs needs +8 DB more power to reach the same sound level as the other speaker in the pair.

I have not taken the backs off the speakers yet, but I am reasonably certain the cracked compression driver is the source of this issue.

Anyone else have this symptom where a cracked magnet is the problem for low output? The quality of the sound from the "bad" side is not impacted, I think.

grumpy
08-13-2016, 12:45 PM
Sounds probable and worth checking further. Chips in the magnet aren't usually much of an issue other than indicating a hard or poorly cared for life, cracks are a different story. I would put it in paperweight status once you have a replacement (after problem verification).

ivica
08-14-2016, 03:58 AM
Score another one for the great folks on E-bay who sell busted stuff.....

Several years ago, I purchased a pair of 2426 compression drivers from a cat in Maryland. Since I only lived a couple of hours away, I drove down and picked them up. The rubber bumper piece that protects the magnet was not seated properly, so I took it off when I got home.

I found a BAD crack in the ceramic magnet. The seller refused to take it back, however.

Anyway, I put a large hose clamp around the magnet and the driver appeared to work just fine.

Fast forward to today - about 6 years later. This speaker system, a pair with 2226, 2426 and 2405s, is now acting up. One of the pairs needs +8 DB more power to reach the same sound level as the other speaker in the pair.

I have not taken the backs off the speakers yet, but I am reasonably certain the cracked compression driver is the source of this issue.

Anyone else have this symptom where a cracked magnet is the problem for low output? The quality of the sound from the "bad" side is not impacted, I think.

Hi robertbartsch,

It is possible that a magnet can be demagnetized after sudden strong bump had happened, but or be sure, first I would open it and see how the diaphragm look like. May be some dirt is in the gap, so clean it.
If gap is leaned, You can try to see what would happen when put diaphragm from the other driver. If again too low efficiency is present, then I would suggest to by another 2426 "motor". From time to time it is offered on eaby.com or elsewhere
http://www.ebay.com/itm/ONE-JBL-2426J-H-F-DRIVER-fully-perfect-working-/272329840471?hash=item3f681f9757:g:FOcAAOSwXeJXesU d
and to use your original diaphragm (if it is original JBL).
May be the diaphragm has some imperfections, or acoustic absorb-foam dropped on the diaphragm....

I wish You success in the "operation"

Regards
Ivica