Be aware of this when refoaming old speakers

[Flodstroem]

Listen to this:

A recently refoamed pair of 2215H didn´t sound any good (rubbing or scraping voice coils it could be)

When cutting of the dome/dust cap in the center of the cone I discovered some bad thing and there it was, a rotten "vent foam" (I call it vent foam because I don´t have any other name for it)

The foam at the pole pieces vent was factory glued by JBL to prevent dust and debris to reach the magnetic gap. Now they was rottened and had completely fallen to pieces (a paradox??!!) The whole magnetic gap was full of this damn rottened and glue-like black debris so the loudspeakers had to be re coned.

When refoaming old loudspeaker modells with rotten surrounds where there is a vent at the rear of the magnet assembly: check for there is no such foam installed at the pole piece. It could be hard to discover, use a good lamp and look through the vent net at the rear of the magnet. If there is a foam at the pole piece installed, then you have to gently remove the dust cap at the front of the cone and remove the old " vent foam" and clean up the gap/ pole piece

Has anybode had the same experiences ?

By the way, thanks Bo for your excelent " manual" in refoaming. It was/is a god help when refoaming loudspeakers

:cheers:
Best Regards

[4313B]

Originally posted by Flodstroem
Has anybode had the same experiences ?Oh hell yeah! Plenty! And JBL doesn't include them in the recone kits :banghead:. Order extras. :p

[boputnam]

Hey, Flodstroem...

Glad it was helpful. Giskard encouraged me to go to the effort, so duly attributed.

In later versions, JBL stopped with the foam and went to a gauze-like fabric covering, and in some, a metal screen. The idea was ventilation and hoping to keep debris from entering. Ironic the decrepitating foam itself became debris... :(

[Flodstroem]

Did forget to attach pictures -here is one

[Guido]

Originally posted by Giskard
And JBL doesn't include them in the recone kits :banghead:. Order extras. :p

Isn't it right to cut some of the foam that fixes the cone inside the cone kit carton and use this?
:confused:

[4313B]

Originally posted by Guido
Isn't it right to cut some of the foam that fixes the cone inside the cone kit carton and use this?
:confused: Maybe. Never bothered as it isn't the exact same density or thickness as the originals and the originals are available for the asking. Probably doesn't matter...

[GordonW]

I wouldn't use the foam from the kit packing. Not enough airflow.

What I do, is to get a piece of (preferably metal) window screen mesh, and glue it on where the foam was (usually use accelerated superglue or epoxy). That's equivalent to the screen JBL used on the later models- I've never had a problem with one like that.

Also, on the ones clogged up with foam residue- I've managed to clean out that stuff without reconing. Remove the dustcap, and take some DeOxit on a foam Q-tip, pull the cone/voice coi as far outward (forward away from the magnet gap) in its travel as you can without forcing or damaging it, and swab out the debris. As long as it's not rubbing/"damping" the voice coil motion, the little bit of extra mass is DEFINITELY not enough to be audible...

Regards,
Gordon.

[franz]

Hi there!

from what I´ve seen at some JBL woofers (K /E 130, 140, 145, 2235, etc.) the mesh over the back ventilation is one of the worst design features in JBL woofers! The older slitted alu decals had even less aperture to let the air pass.
If you sweep the speaker at high excursions some very bad noise can be heard from the compressed air forced through the narrow constrictions. I suspect that it can also be heard in some way on the speaker front.
Other well know brands do much better here IMHO with their much bigger vent openings. More recent JBL motor structures seem to be better engineered in that respect.

Greets

Franz;)

[Flodstroem]

Gordon, thank you for your tip to use a type screen mesh over the vent hole.

"Also, on the ones clogged up with foam residue- I've managed to clean out that stuff without reconing. Remove the dustcap, and take some DeOxit on a foam Q-tip, pull the cone/voice coi as far outward (forward away from the magnet gap) in its travel as you can without forcing or damaging it, and swab out the debris. As long as it's not rubbing/"damping" the voice coil motion, the little bit of extra mass is DEFINITELY not enough to be audible..."

Well Gordon, this work could be done only if the voice coil former is unperforated with small vent-holes. This is not the case with the coil former at these 2215H. They have a lot of small vent holes in the coil former. The debris from the vent foam is all around under the spider and the dome, you can make a bet on that. Its not possible to reach the outside of the voice coil to have the cleaning work done, with the cone and spider still glued in place. If it was possible to loosen up the glue at the spider, cutting the surround and have the cone loosen, then it would not cost as much as two cone-kits, only the costs of two new surrounds ?
How about to use MEK as solution ? Has anybody tried it?
:hmm:
Best Regards

[4313B]

I agree Franz.