To Shim OR Not To Shim ?

[RLock]

I started refoaming speakers about a year ago. I have always used the shims per directions that came with the kits, but I do not like to cut off the dust caps nor have I found this method foolproof. Reading these postings it seems the professionals use a test tone generator while listening for he VC rubbing thus saving removal of the dust cap. I recently had good luck refoaming my cars 8" sub without either and simply feeling for the least resistance per the directions while gluing the surround in place. Every time I botch a refoam I have to start over, sacrifice a surround and potentially damage the cone. It seems to me this is both art and science. Can someone chime in to what method is actually recommended by JBL.

[audiomagnate]

I started refoaming speakers about a year ago. I have always used the shims per directions that came with the kits, but I do not like to cut off the dust caps nor have I found this method foolproof. Reading these postings it seems the professionals use a test tone generator while listening for he VC rubbing thus saving removal of the dust cap. I recently had good luck refoaming my cars 8" sub without either and simply feeling for the least resistance per the directions while gluing the surround in place. Every time I botch a refoam I have to start over, sacrifice a surround and potentially damage the cone. It seems to me this is both art and science. Can someone chime in to what method is actually recommended by JBL.

I'm no pro, but I use the tone method and it works for me.

[Ed Zeppeli]

Can someone chime in to what method is actually recommended by JBL.

JBL don't re-foam their drivers they re-cone them so as far as I've heard, they don't have a recommended procedure for re-foaming.

[ivica]

JBL don't re-foam their drivers they re-cone them so as far as I've heard, they don't have a recommended procedure for re-foaming.

Hi,

Unfortunately You are right. And that is the reason why we can not hear , for example, 2231A again. Its 'appropriated' recon-kit C8R2235 would not produce original sound, unfortunately.
I can tell the same for the initial series of 2245H too, even re-coned with C8R2245 kit.

regards
ivica

[SEAWOLF97]

I've refoamed literally hundreds of drivers.

Did the shim method on the very first 2 , now all are done with the Yoda method with no problems.

[audiomagnate]

I've refoamed literally hundreds of drivers.

Did the shim method on the very first 2 , now all are done with the Yoda method with no problems.

Ask I have to the reason for that name Yoda?

[JuniorJBL]

I've refoamed literally hundreds of drivers.

Did the shim method on the very first 2 , now all are done with the Yoda method with no problems.

Ah very good young padawan!

Control, control, you must learn control!


:p

Cut the dust cap you must not!

[SEAWOLF97]

Ask I have to the reason for that name Yoda?

Use THE FORCE as your guide.

put your basket glue on (2) (after gluing to the cone has dried (1)) , then work the cone in & out from different positions , listening and feeling & using your brain (THE FORCE) for scrape , until it's perfect ..then clamp it down. EZ.

but #1 & 2 get reversed on a LE-14h-1 .. weird , no room to adjust on the lip of the basket on that driver (and some Altecs too)

[Allanvh5150]

I never use shims to re foam as I hate cutting off the dome also. Re foaming is sometimes the only option as out friends at JBL do not make cone kits for everything. And, for us in the Antipodes, a re foam kit is $20 as opposed to a re cone kit at sometimes $600 - $700!!!

Allan.

[audiomagnate]

Use THE FORCE as your guide.

put your basket glue on (2) (after gluing to the cone has dried (1)) , then work the cone in & out from different positions , listening and feeling & using your brain (THE FORCE) for scrape , until it's perfect ..then clamp it down. EZ.

but #1 & 2 get reversed on a LE-14h-1 .. weird , no room to adjust on the lip of the basket on that driver (and some Altecs too)

I know how to do it, but why do you call it the Yoda method? Did he invent it and send the info back to the past?

[Allanvh5150]

Yoda was from a long time ago, in a galaxy far far away. :)

[jbl]

It depends. The Tone Method may not be an option on drivers with foam filters. If the foam turned to goo, cutting the dust Cap to remove the debris is the only solution. From there a shim is needed if the foam surround needs to be replaced.

[RLock]

I went over to the "dark side" for a short period when I purchased another brand of speaker and actually thought they sounded better ("The Farce"). Now, the force is with me.

[subwoof]

the filter, forget not.


Glued to the top plate ( under the dust cap that lazy refoamers ignore ) on most JBL ferrites is a small piece of foam that is the defacto air filter for the vent at the rear of the magnet. You can see this through the metal screen on the back on most speakers.

Back when JBL used alnico's this was a lattice (coated ) of some string or fiber that resembled grandma's kitchen chairs. It NEVER rotted or came apart so was just ignored.

BUT THEN the bean counters at JBL decided that saving .04 cents per magnet by using a piece of foam was a good idea. DOH!

HOWEVER the same "ten years at best" lifespan was then introduced ( it's the SAME foam as the surround ) in a place you COULD NOT SEE and MANY MANY of the music instrument speakers ( E120/130/140/145/155 along with the professional models ( a bazillion..) suffered from a common malady.

The "foam" would devolve and disintegrate into it's original petroleum GOOP and find it's way into the voice coil gap. Where it would ( if UNBELIEVABLY LUCKY ) dry out and turn to dust and get blown out the vent or ( NOT UNBELIEVABLY LUCKY ) turn into a slice of glue and bind the coil / overheat / cause distortion / JAM and otherwise ruin a perfectly good speaker.

Now those that do not remove the dustcap and/or shim are fooling themselves into thinking using a tone generator is just as good... Well because most consumer speakers have a somewhat longer / easier life it's possible to see that BUT in reality, no.

BTW the paper caps ALSO turn into brittle shells and fall apart...pokey pokey

Caps are cheap
Shims are cheap
Glue is cheap

Talk is cheap

Experienced rebuilders are VERY cost-effective

Recones ( if still available ) ( Si senor' ) are VERY EXPENSIVE

say as I do, not as I mean

sub

[Ed Zeppeli]

Interesting. I just pulled the old cones off two 2205s to have them re-coned into 2235s and one had the (dissolved) foam filter and the other had a lattice version that you speak of. Both are ferrite versions of the driver; not he 2205A.

Is that little filter critical?

Thanks,

Warren

[subwoof]

the 2205H is a one-year model between the alnico and ferrite 2225..could be gray, could be black. magnet with long bolts or short ones..foam filter or old style...

potluck. It was a very frantic transition those years. I worked for a JBL dealer then and you NEVER knew what was in the box / cabinet when it came in.

sub