Refoaming and dust caps
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Doug G.
Lunatic Member
I don't shim when I just refoam but I have repaired speakers also and I have replaced the dust cap with a larger one. These had cloth caps.
However, ideally you should cut the original one out right next to the cone and then glue it back into place when done. You can leave a very small spot attached so it's easier to get back into correct position.
This is more critical with paper or metal caps in that a different size cap may affect the sound of the driver. A cloth cap of a different size won't make too much difference.
Good luck.
Doug
However, ideally you should cut the original one out right next to the cone and then glue it back into place when done. You can leave a very small spot attached so it's easier to get back into correct position.
This is more critical with paper or metal caps in that a different size cap may affect the sound of the driver. A cloth cap of a different size won't make too much difference.
Good luck.
Doug
mikeybc
Listener
This is what I have done and if your not sloppy with glue you'll never know it was cut. Many people will shy away from buying a speaker with non-original dust caps.
avguytx
Lunatic Member
I try to reuse the original dustcaps if they are in good shape but it depends on if it's a woofer that needs shimming more so than others. IF you want to remove and reuse the original dustcap, try using MEK (methyl ethyl keytone) with a syringe around the base of the dustcap. This will loosen the glue and make it easy to remove. I also use MEK to remove old glue from the surrounds on both paper and poly woofers with great success. I learned this years ago from my friend that rebuilds speakers for a living. Works like a champ!
alwaysjammin
Vintage like my gear
This is pretty much my method but I use acetone in an eyedropper. I also learned the technique from a guy in the speaker rebuilding business. Just don't over apply whatever you use. I did encounter some adhesives that laughed at acetone and I had to cut the caps.....MEK may have been a better choice for those....I'll have to try it next time. I've shimmed all the drivers I've refoamed just to be certain everything is centered correctly. Never had an issue with any of them using this procedure.
avguytx
Lunatic Member
Seems like the Ace I went to in TX (when I lived there) didn't have it but Lowes and Home Depot have it back in the paint section where the paint thinner and mineral spirits are.
no more
I haven't cut the caps and shimmed since my first pair. I carefully center when replacing the surround. I only had one near issue with a set of baby Advents (they were sort of cursed somehow, lot of strange on them). Anyway, the ones I did cut and shim were a "kit" for the speakers and the new centers were slightly larger to cover the remains of the old center so I didn't have to scraps all the way to the cone surface. They were Large Advents.
I've seen MEK at my hardware store. Not sure who they really are. True Value and/or Coast-to-Coast. Paint section of a decent hardware store or a paint store has all the good chemicals. I like Acetone for a lot of stuff but haven't tried MEK. Probably need to add that to my shop.
That is the ONE thing about refoaming that gets me. All the black tar that gets all over the place cleaning up the speaker. Acetone works pretty well but I'll try something else if it is better.
I haven't cut the caps and shimmed since my first pair. I carefully center when replacing the surround. I only had one near issue with a set of baby Advents (they were sort of cursed somehow, lot of strange on them). Anyway, the ones I did cut and shim were a "kit" for the speakers and the new centers were slightly larger to cover the remains of the old center so I didn't have to scraps all the way to the cone surface. They were Large Advents.
I've seen MEK at my hardware store. Not sure who they really are. True Value and/or Coast-to-Coast. Paint section of a decent hardware store or a paint store has all the good chemicals. I like Acetone for a lot of stuff but haven't tried MEK. Probably need to add that to my shop.
That is the ONE thing about refoaming that gets me. All the black tar that gets all over the place cleaning up the speaker. Acetone works pretty well but I'll try something else if it is better.
Coconuts 500
Active Member
Don't put the dust cap back! Removing it will in almost every case improve the sound of the speaker drastically. You do not need to worry about dust getting inside the speaker, it is extremely unlikely, unless you pour sand in there. If there are small holes in the cone under the dust cap, you can glue thick but small pieces of paper on the underside of the cone to cover them up. Works like a charm.
Doug G.
Lunatic Member
How does leaving the dust cap off "improve" the sound of the speaker "drastically?"
Anyway, another good solvent to have around when repairing drivers is lacquer thinner.
And yes, in spite of my first post, the preferred thing to do is remove the cap with a solvent and replace it after.
The only exception may be if a water soluable glue was used. It will probably take more water to soften the glue than is desireable before the cone gets too wet. That would be bad.
Doug
Anyway, another good solvent to have around when repairing drivers is lacquer thinner.
And yes, in spite of my first post, the preferred thing to do is remove the cap with a solvent and replace it after.
The only exception may be if a water soluable glue was used. It will probably take more water to soften the glue than is desireable before the cone gets too wet. That would be bad.
Doug
tmad40blue
"I can hear forever!"
:scratch2:
If this were true I'm sure at least a few of those incredible driver designers out there would have figured it out by now...
I've only re-foamed 1 set of speakers without shimming. A pair of bose 901. The speakers have a relatively short travel, so I felt safe not shimming them. I just glued the foam and pushed the speaker in and adjusted as necessary to avoid any coil rub. I would think when you get into some of the woofers that have a longer throw, you wouldn't have much of a choice other than shimming.
That being said, I believe the most popular method is to use a test tone.
That being said, I believe the most popular method is to use a test tone.
elgato8905
Nobody special.
Refoaming a pair of 901's pretty much counts as doing three or four sets of speakers:yes:.
I personally have refoamed A LOT of sets of speakers. I've been doing it for years and have done more than I can remember. They've all came out great and I've never taken the dust cap off of any of them. I just do it by feel. It always works for me.
Agreed. While it's not really necessary to shim on drivers with a (relatively) wide gap, it's a very good idea with drivers that are notoriously difficult to refoam.
If you use a very sharp, pointed hobby knife, like an X-Acto knife, you can carefully cut the old cap close to the cone, and leave a 1/16"-1/8" flap of dust cap uncut. Fold it back like a hinge and it won't be in the way while you shim. Then, when you're all done and you fold it back over, the cap will align perfectly with your cuts, and if you reglue it carefully, you'll never be able to tell it was cut at all.
As far as not replacing the dust cap, I would strongly recommend against such a practice. Dust getting into the v/c gap is not the issue. The problem is that the driver was designed and engineered to have very specific performance characteristics, and those characteristics are dependent on the driver being in the same configuration that it was in when it left the factory. If you remove the dust cap, it will NOT perform as intended. And it won't be an improvement.
HiFiCanada
Caregiver
What about the bigger 18in drivers, I got the JBL, 2245h driver that needs a new surround, are the bigger ones not harder to do?
cubby01
aka Buck
A 30 Hz or 40 Hz test tone, just enough volume to excite the coil which naturally centers within the magnetic field and you know right away if the coil is rubbing (without yourself pushing on the cone) so you just adjust the surround position on the frame while the glue is still wet. A couple popular surround sellers provide CDs with the tones and detailed instructions along with their kits.
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