LE-10H repair

[Ralph856]

Hi

I have a pair of LE-10H's that were refoamed by a local speaker repairer, but within several months had started audibly distorting when playing deep bass music, such as dub.

I took them back to that same company and they told me that the black foam, near the centre dome polepiece hole, had disintegrated and had fallen into the gap.

They said it took 2 hours of labour (£100 or $155) to repair both drivers but that they are now 'as good as new'.

Not being a technical person, I'm just interested to know if all this sounds credible and genuine?

Incidentally, I did raise the question as to why they hadn't noticed the issue when they had done the refoam several months earlier but didn't get a clear answer back on that. I guess it's conceivable that the deterioration took place during those seven months .

Thanks

(BTW- this is not to be confused with a different set of LE-10's that I made a thread about recently)

[Audiobeer]

Yes it is credible and it happens. I remove those pesky disenegrating POS on all my vintage JBLs. I sold a pair or freshly refoamed 4313B's only to have it come bach within days due to the inability of one of the woofers to move. 40Hz and it buzzed. After a little research and removal of the dust cap the exact thing you described had happened.

[rdgrimes]

Getting to the point where that piece of foam should be removed on every woofer re-foam job, but almost nobody does it. It might be the most common cause of failure in old drivers.

[Ralph856]

Many thanks! That's good to hear, although the combined cost of the original refoam plus latest repair would have bought a damn recone! Shame they didn't have the foresight to remove it previously.



I do have another question about refoams because I need to get my other pair of 'NIB' LE-10's done:

I called a different company to the one mentioned above and they told me that when they do a refoam of an old driver, they replace the back suspension at the same time (with a non-JBL part incidentally). Aren't refoams usually just the surround (plus that piece of foam, if you're lucky)?

[rdgrimes]

I called a different company to the one mentioned above and they told me that when they do a refoam of an old driver, they replace the back suspension at the same time (with a non-JBL part incidentally). Aren't refoams usually just the surround (plus that piece of foam, if you're lucky)?

If that refers to the spider, one wonders whether just doing a re-cone would be better. If your spiders are in good shape, no sagging, why replace them?

[Ralph856]

If that refers to the spider, one wonders whether just doing a re-cone would be better. If your spiders are in good shape, no sagging, why replace them?

Hmm, I guess he must have meant the spiders, then.

Yeah, those NIB drivers should have non-sagging spiders, if nothing else, having been supported in their boxes- so no need to replace them or do a recone from that perspective.

[DogBox]

Nothing else....

[DogBox]

Just a Question: The "foam piece" that covers the pole-piece vent-hole - evident when you first take out the old dust cap- Are they really necessary for the function of the speaker? Besides keeping foreign objects and grit from finding it's way into the coil gap?
I'm in that transition point myself and was thinking of a) replacing it with something else as acoustically transparent, b) leaving it out altogether and relying on the foilplate gauze on the back to be adequate. Interesting thread...

DogBox

[4313B]

Prior to the foam discs JBL used phenolic mesh over the vent. The phenolic mesh wasn't sufficiently dense to do the job. I suppose grille cloth would work just fine. It's easy to cut a nice little cloth disc. Impregnate it with resin and make your own phenolic material that will last longer than you will.

[DogBox]

wasn't sufficiently dense to do the job....

Hi 4313B, So, it "did" have a job to do...? What was it put in there for?
I would have thought it would give resistance to the flow of air behind the dust cap..???
Thanks,

DogBox

[rdgrimes]

Keeps bugs out, for one thing.