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Speaker Surround Dope For KLH and AR speakers


DonT
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Hi all. I posted about this over a year ago. I am now almost positive it will work great on our vintage speakers. I am now going to test it on a pair of KLH 24's I have. As you can see in the video after a year and 3 months of sitting out in the open air (Why it's so dirty) it has not hardened at all. As I test it further I will post more info. I will say that the main ingredient is rubber cement and you do need toluene to thin it. But this stuff is so gooey you almost don't need to thin it to apply it. I am not trying to start any debate about existing products I am just posting my progress with mine. Thanks  

https://youtu.be/8S5n69AelK8

IMG_0003.JPG

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Understood about no debate regarding various products for this purpose and I agree with that.……being said IMHO no doping of any kind should be done. That is a road that eventually ends badly.

There is the most important thing to understand and that is the difference between acoustic suspension vs. a vacuum seal, which these speakers are not. That means the surround can’t be saved eventually no matter what you do or what you apply. Better to put the effort into replacement instead. High quality replacement surrounds are more durable than some of the material used decades ago. I’ve also seen doped surrounds where they fall apart on the backside….most do not go so far as to get back there, (and it won’t matter any way)

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2 hours ago, newandold said:

Better to put the effort into replacement instead. High quality replacement surrounds are more durable than some of the material used decades ago.

The dope is for cloth surrounds--not foam. The KLH Service Bulletin in our Library instructed repair centers to always re-dope all KLH cloth-surround drivers. I can tell you from experience the application of the correct dope made a night & day difference on my KLH Model Fives.

4 hours ago, DonT said:

I posted about this over a year ago.

Yes, and that thread wound up in the Kitchen. The sealant Roy cooks up is authentic butyl-based (the stuff KLH and AR used) and has been available for a few years from Vintage_AR on ebay or directly from Roy on this site. IMHO it is unwise to put anything else on our valuable speakers.

Edited by JKent
Used the wrong word. The rubber is butyl.
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26 minutes ago, JKent said:

The dope is for cloth surrounds--not foam. The KLH Service Bulletin in our Library instructed repair centers to always re-dope all KLH cloth-surround drivers. I can tell you from experience the application of the correct dope made a night & day difference on my KLH Model Fives.

Yes, and that thread wound up in the Kitchen. The sealant Roy cooks up is authentic nitrile-based (the dtuff KLH and AR used) and has been available for a few years from Vintage_AR on ebay or directly from Roy on this site. IMHO it is unwise to put anything else on our valuable speakers.

I stand corrected to you guys.

My focus was not on cloth surrounds. How long on average would you go with cloth maintenance before replacement?

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1 hour ago, JKent said:

 

Yes, and that thread wound up in the Kitchen. The sealant Roy cooks up is authentic nitrile-based (the dtuff KLH and AR used) and has been available for a few years from Vintage_AR on ebay or directly from Roy on this site. IMHO it is unwise to put anything else on our valuable speakers.

Actually the original stuff is butyl rubber. I don't have it saved anymore because I changed computers but there was a paper put out by I think KLH that talked about re sealing the cloth surrounds back in the day. It said that if the "Buytl rubber compound was to thick you just needed to thin it with toluene. Plus in my post from a year ago Roy asked me if i used "butyl rubber, like the original" This is why I have used rubber cement. Rubber cement (cow gum in British English) is an adhesive made from elastic polymers (typically latex) Link  (https://en.wikipedia.org/wiki/Rubber_cement) . Latex is natural rubber look here (https://en.wikipedia.org/wiki/Natural_rubber ) So my sealer is made of the same stuff they originally used.

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Yes, butyl. Temporary brain fart. This is the KLH Service Bulletin: http://www.classicspeakerpages.net/library/klh/other/klh_schematicsservice/klh_service_bulletin_60.pdf

Thank you. I went back and corrected my error. I had referenced the Service Bulletin but clearly did not re-read it!

Obviously, I'm not a chemist. But a quick Google search showed that butyl is synthetic, not natural. What difference does it make? I have no idea. Just sayin' it seems wise to stick with the tried and true (and original).

People have put all kinds of weird stuff (latex caulk for example) as well as "seemingly" appropriate stuff (Permatex) on their cloth surrounds with disastrous effects. I would only use what the Service Bulletin recommends.

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Don,

Do you have the ability to take woofer frequency response measurements?

Like, before and after application of your sealant. Then again in 6 months then 12.

I'd think free air resonance measurements would be critical to determining the effectiveness of the sealant.

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On 3/3/2022 at 9:25 PM, 1rebmem said:

Don,

Do you have the ability to take woofer frequency response measurements?

Like, before and after application of your sealant. Then again in 6 months then 12.

I'd think free air resonance measurements would be critical to determining the effectiveness of the sealant.

No but it is one thing I am looking into. I really need to get that ability. It is no rush, I have let this sit for over a year at this point so I will take my time and do exactly that.

 

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On 3/2/2022 at 7:48 PM, JKent said:

Yes, butyl. Temporary brain fart. This is the KLH Service Bulletin: http://www.classicspeakerpages.net/library/klh/other/klh_schematicsservice/klh_service_bulletin_60.pdf

Thank you. I went back and corrected my error. I had referenced the Service Bulletin but clearly did not re-read it!

Obviously, I'm not a chemist. But a quick Google search showed that butyl is synthetic, not natural. What difference does it make? I have no idea. Just sayin' it seems wise to stick with the tried and true (and original).

People have put all kinds of weird stuff (latex caulk for example) as well as "seemingly" appropriate stuff (Permatex) on their cloth surrounds with disastrous effects. I would only use what the Service Bulletin recommends.

Thanks, I was looking for that and couldn't find it.

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