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Quick and dirty foam revival

D

dbCO

New Member
Has anyone ever tried spray rubber sealant to refresh very old, but still intact foam surrounds. I'm thinking of removing the drivers, masking the cone and spraying a layer of rubber over the foam surrounds. These obviously are not audio treasures. I have done dozens of surround replacements but these have always been after the foam was no longer intact.
I understand that the Fs may change but these are only less than top notch JBLs.

Thank you for any thoughtful input. dbCO
 
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I just ordered X-Protector from Amazon. I'll find something in my speaker debris to test the concept before unleashing it on Walmart level JBLs.
 
If you can get away with just a thick enough layer of the spray foam to hold the surround together, whay not give it a try? Experimenting one less than stellar speakers can have interesting results. Ive done it. Sometimes it doesn't work out, sometimes it does. The last two pairs I experimented on cwme out sounding better. Both pairs were freebies. One pair was just unlistenable in stock form.
So I say go for it! :thumbsup:
 
dbCO said:
I understand that the Fs may change but these are only less than top notch JBLs.
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vinylkid58 said:
It would be an interesting experiment to measure before and after TS values.
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Total Q is a combination of mechanical Q and electrical Q. Spraying the foam surrounds won't change electrical Q and I doubt the mechanical Q will change much because the spider is responsible for much of that, so I say it's worthwhile to try the spray.
 
vinylkid58 said:
I'm more interested in the change in Fs.

jeff
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Fs is a "weight on a spring" type of effect. The spring in the case of a speaker is the stiffness of the spider and the surround, and the weight is the mass of the cone. The spayed-on rubber will add a bit of mass, but I'd guess not enough to be significant. The stiffness of the spider will be unaffected, so that leaves the stiffness of the surround as the variable which may change. My guess is that Fs won't change much, if at all, because the spider is providing most of the stiffness.
 
Keep in mind, we are talking about Goodwill JBLs here. The audience for these speakers is not that discerning.
 
do it- and post pics, don't care what it sounds like, just want to see what an application of this stuff looks like
 
dbCO said:
I understand that the Fs may change but these are only less than top notch JBLs.
Click to expand...
JBL made numerous excellent speakers that were "only less than" their "top-notch" models

Which speakers are you considering doing this to? Can you post some photos?
 
I would have one (serious) concern. There might be a solvent in the rubber spray that reacts badly with the foam. It would be a disaster if the foam just dissolved.
 
Simply Speakers currently sells a coating product they call foam guard to coat foam surrounds. Its liquid vinyl. I have used it with what I consider good results. Its pretty inexpensive.
Also, more than 20 years ago, I stumbled on a company that makes all types of coatings called the Lord Corporation. I was able to get a small sample of their Butyl Latex product BL-100. I have coated many foam surrounds with this coating. More than 20 years later, those surrounds are still intact although the product has stiffened up somewhat.
When the foam dries out over time, it loses its elasticity and will flake apart. These coatings will act like a glue to hold the foam together. It will certainly delay having to do a re-foam.
 
Interesting idea. Could be worth some trial if you experiment on some woofers you don't care about. Would you do both sides of the foam? Could be tough to get in from the back side.
 
I did coat some surrounds on the inside as well. Not easy, but can be done. I ultimately decided that inside coating was not necessary. Remember, the more coating you apply increases the chance you will alter the sound of the driver. All the speakers I coated were important to me. All are still up and working today.
 
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