View Full Version : Woofer refoaming
07-07-2003, 02:45 AM
Does anyone know or can recommend a person or shop that does excellent work on refoaming woofers.
I had a pair of woofers refoamed recently and the person did a job similiar to the woofers on the Jubals here on Ebay.
The leading edge of the surround is glued to the front part of the cone instead of the back!!
Since they were not for me, I wasn't too upset but I want the woofers to look original.
Is this a new style or just laziness??
I have a mint pair of woofers that need new surrounds and I would like for them to look NICE and original.
Any help would be appreciated.
Thanks in advance.
07-07-2003, 08:51 AM
So far as I know, putting the surrounds on the front doesn't ruin the woofer, but may alter it's performance slightly - Giskard and others could answer that definatively.
No, it is not a "fad" to put surrounds on the face - it is easier and faster, but is not correct for that woofer. Only the LE14 series (I think...) had different iterations that had surrounds mounted first on the rear, and later on the face. Regardless, resurrounds should be done identical to the original that was removed.
There are two locals that get referrals here - Orange County Speaker supply http://www.speakerrepair.com/ - they will do the work for you.
Another is Rick Cobb - email at email@example.com. Rick sells proper fitting kits, and will do the resurround too, if need be. The work is not hard, only a bit tedious, and time consuming. And, you need be careful and get things centered.
07-07-2003, 09:41 AM
This guy has been doing work for me for over 20 years.
Florissant, MO (St. Louis)
His most recent work for me was to refoam an LE15. He also did one of the old lansaloy LE14a's which was extremely difficult because the surround had to be pieced together. No one makes a kit for that particular style of LE14a.
He also has a wide assortment of obsolete parts. He's an authorized JBL repair station.
This message comes from JBL Dog :cool:
07-07-2003, 10:50 PM
We also do refoaming and other vintage speaker restoration where I work:
We occasionally have speakers mailed to us via UPS and FedEx... sometimes they just seem to show up out of the blue, with a note in the box. As long as we know where they come from, how to get hold of the owner to get payment info, and where to send them, we're OK with that, though... :)
(and yes, I guarantee I will put the surrounds on the BACK of the cone on a JBL! :D )
In seriousness, it does make a small difference whether the surrounds are on the front as opposed to the back. It will change the rest offset of the woofer, sometimes as much as a millimeter, depending on the stiffness of the surround vs. the stiffness of the spider. That can cause quite a bit of even-order harmonic distortion, due to the induced asymmetry in the motor by the surround causing the woofer to rest at a non-midpont of the voice coil, from an excursion standpoint...
Besides, as Giskard put it, it just looks like #&$^ when they're put on from the front... :D
07-08-2003, 02:59 AM
Bo, JBL Dog (great name) and Gordon,
Thanks for the quick replies!!
I never considered the effect on the proper operation of the woofer, In fact, I thought it added a little xtra bass to the L166 when I listened to them.
Yes Gordon, I think it just looks horrible and I don't want my woofers to look like that!!!
07-08-2003, 08:34 PM
Many quality cone drivers do have the surrounds outward mounted but this has not been the JBL preference. I side with the comments on the “proper aesthetics” side of this issue though I would be surprised if I could tell any sonic difference caused by the different mounting of the surround. I can not say this from experience, but I have been told that there are times when the old foam/glue simply to not allow a clean removal and the result is a ragged surface to try to remount the new surrounds. It may be a good idea to tell the shop upfront that you want the original back-mounted installation and get their feedback prior to mounting the new surrounds.
07-08-2003, 09:26 PM
Yep... many manufacturers do put the surrounds on the outside of the cone, and by all means, they should STAY that way, if they started that way.
However, in the case of JBL, the geometry of the cone/voice coil assembly (where the cone is placed on the voice coil, to have it all rest at the right point in the excursion path) is built around the surround being on the back of the cone. So, to make sure that the woofer motor is aligned properly forwards-backwards in the gap, they need to have new replacement surrounds installed the same way.
As for the ragged leftover glue issue- I've found that with JBLs, instead of scraping the foam off, a VERY light scoring of the paper cone with an Exacto knife, (just enough to make a mark in the paper, basically) all around the cone, on the backside of the cone right at where the surround stops and the cone starts, usually allows a careful rebuilder to just pick at, pry up and peel off the entire old dead surround, glue, foam and all, with just the TINIEST layer of paper with it. This will usually leave a nearly PERFECT surface, just waiting to have glue applied and a new surround applied.
In fact, I just got through rebuilding a recently-rescued-from-a-speaker-boneyard pair of PR8s (probably from a pair of L66s, AFAIK) this way, today... turned out spiffy, if I do say so myself!
07-08-2003, 09:41 PM
"for the ragged leftover glue issue"...
I personally strive to not take any paper - either along the front edge, nor the immediate back-side lip. And, where paper has begun to come away with the glue, I tend to leave it alone, rather than risk any thinning to the important cone edge. In these instances, I will pin-point some glue to reattach this.
I fastidiously and very gently scrape the old remains off - going around and around again with an always-new Xacto #10 curved blade, propping the cone-edge up on a 1/2-in scrap of clean birch to minimize mis-orientation of the coil.
Recently, in limited cases and on some cones where the basket provides sufficient space, I have used a Dremel at half-speed with a very fine-grit flat-edge stone to remove ONLY the easiest-to-remove old glue. I don't recommend this, though, unless you've very, VERY steady hands and good eyes (and lighting ;) ), but this has improved the cleaning markedly (particularly good for old, very hardened Lansalloy surrounds) without encurring any risk damage to the cone edge. However, this doesn't have application to all transducers due to the limited space between the frame and cone edge.
07-08-2003, 11:56 PM
I picked up a clean set of 2245H's on Ebay recently for a reasonable price ($300). Since they were "buy-it-now", I pulled the trigger right away. They did show up with the surround redone on the outside.
I asked Lloyd @ Spectrum Sound if I would notice any difference. He said the sound could be slightly altered, but I probably would not notice any difference. He added the voice coil will sit a little lower in the gap.
Not something you would want to do if your spiders were weak. :(
This meaage comes from JBL Dog :cool:
07-09-2003, 07:59 AM
Well, as for paper thinning... my method is, after peeling the surround, to soak white glue into the paper, where the peel took place. This, IME, more than makes up for any loss of stiffness due to the thinning of the paper.
In fact, if I'm using some of the new polyether surrounds (as opposed to the old polyurethane, which was subject to attack from airborne fungus, and in fact this is what causes almost all foam surround rot), since they're NOT succeptible to airborne attack and generally last 2-3 times (or more) as long as the original surrounds, I frequently just use white glue to attach the new surround to the cone as well. IME, it makes for an overall stronger (and MUCH stiffer) joint, due to the fact it soaks into both the paper and foam. Very good thing when dealing with the brittle Lansaplas woofers. Also, the extended repositionablity of white glue (ie, the slower drying), allows for a fail-safe, always dead-on straight, even application of the surround. Most times, even pros can't tell that the surround is a replacement, after this procedure!
I've done the scraping and grinding methods too... the only problem is, that the probability of damaging the cone by bending, cutting, tearing or wrinkling it while applying the necesary force to scrape stubborn deposits, or by just plain OOPS, the grinder or blade slipped, accidents, IME outweighs the necessary evil of taking off a tiny layer of paper with the old surround. Any little bend accidentally done to the cone, and bam, there goes a crack in the Lansaplas. I've had to stabilize and fix this sort of damage before, where someone attempted to do a clean by mechanical means...
07-09-2003, 08:16 AM
"or by just plain OOPS"
Whichever way, it is simply a time-consuming and tedious task where I have come-up with no real "time savers".
But, it is a job best done correctly - the satisfaction of being well done, is long lasting. ;)
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