View Full Version : 2470 coil blown-why?

07-17-2008, 12:56 PM
Hi everybody,

I'm absolutely new to this nice forum, and my first post is a question, as you might see;)
I have a nice horn system on loan with a JBL 2470 with phenolic diaphragm, which is my first horn speaker in my livingroom btw.
Sounds great, or better, sounded great....

When the owner and myself set up the whole thing, we noticed slight distortions from one channel especially with piano music.
So out went the diaphragm, and according to an advice from another horn owner we sanded off a tiny bit of the aluminium ring of the coil.
After this the distortion was gone:applaud:
And the music with it :banghead:

When I measured the coil directly at the diaphragm, it turned out to be dead, no resistance at all.
So the question is: are those diaphragms known for sudden death, or did the sanding hurt something, although it was really almost nothing?
And is it maybe possible to repair?
Putting in a new voice coil should be possible with the right tools, does anyone know if someone ist offering such kind of service?
If there is no chance to bring it back to live, my friend must swallow the toad, as we say in German, and get a new one somewhere, which is not easy as well.

Thanks in advance for any idea!

Best regards from Germany,


p.S.: Horns seem to be quite infectious, as I find myself already watching out for those beasts....

07-17-2008, 11:49 PM
Hi, and welcome to the forum Juergen.

I believe you have to get a new diaphragm. Never heard about "sanding" them to make better sound. Sanding will remove the isolation? on the wire, but those more learned than me will probably climb in.

Anyway, good luck.

07-18-2008, 12:08 AM
If I got this right you sanded the winding of the voice coil?
Thus you produced a short circuit. Ouch! Don't do that again, it can even destroy your amp.

If you need further help PM me, I'm in Germany and have "some" experience with JBL :)

07-18-2008, 03:03 AM
Hi Rolf&Guido,

thanks for your reply;

the sanding was not for better sound, it seemed that the coil was not exactly round/flat at one spot, so this part of the coil touched the magnet and caused slight distortions, as it seemed.
So we sanded that little part; but I couldn't see any wire, its just the ring of aluminium, I thought the wire is underneath the alu ring.

I think I'm going to send mail to you, Guido, maybe its a bit easier to discuss also in my language.
I'll post the results later on....

and already many thanks for your atttention,

and best regards from rainy :(Germany


07-18-2008, 08:00 AM
I'm in Germany and have "some" experience with JBL :)


SOME? You got the most what is needed to know Guido!:D:applaud: