KLH is redope of surrounds needed?

[Soundminded]

I re-doped my KLH-5s using, on Merrylander's recommendation, rubber cement, which I haven't seen recommended anywhere else. But it seems to be a material that, though it dries, doesn't harden. My mistake, unfortunately, may have been using two coats (I tried to keep them thin), because I couldn't tell if I got good coverage on the first. The audible results are very similar to your description - louder, not as low, and with a peak.
I did this in conjunction with a recap, and have a post on the concurrent thread about cap break-in. My best hope is that someting will improve with use.

You might experiment with sovents to disolve the rubber cement. Experiment with it using the same cement you applied elsewhere before you apply it to the speaker surround. You might get lucky and be able to remove at least some of it without damaging the cloth or leaving even larger openings than when you started. Be cautious however. I'd start with acetone, a few alcohols (methanol, ethanol, isopropyl), and MEK (methyl ethyl ketone.) Be careful, these substances are flamable and toxic. When you get to toluene, napthalene, xylene, it gets even worse. Work outdoors or in a well ventillated room and of course, no sources of ignition. Keeping a fire extinguisher handy can't hurt either.

 

[kirk57]

IMHO opinion Roy Cs post really needs be a sticky, as this subject comes up at least 20 times a year, and people continue to put all kinds of stuff on surrounds without knowing the long-term consequences.

Permatex (diluted with lacquer thinner) was the first material we experimented with over at CSP a number of years ago, as it contained a butyl compound similar to what we were looking for. Although it remains tacky for awhile, the gasket sealant eventually stiffens and forms a membrane....which is the problem with virtually all of the compounds discussed in this forum. Once a membrane forms and stiffens, even to a slight degree, fs increases (sometimes dramatically) compromising the design basis of the acoustic suspension woofer. I have tested and measured many compounds over the past 5 years, and the results have been consistent.
It is very often better not to apply anything at all, especially if the speakers are not being pushed to higher volume levels. (A thin application of Permatex is not bad compared to most other treatments mentioned along the way.)

After input from a number of knowledgeable sources, including Roy Allison (early AR and Allison speakers...who is in his 90's now), I was able to come up with something much like the original compound. It is nasty to make, and is essentially the same tacky stuff manufacturers have used to treat ("dope") driver cones and domes to modify response characteristics in the past. It is a non-drying butyl compound diluted in toluene.

Due to the high percentage of toluene, and little demand for this kind of compound today, a commercial product of this type is not readily available.

Vintage AR/Larry Lagace is the only "retail" source of the stuff. AK and CSP forum members are welcome to send me a PM for more information.

Roy

 

[RoyC]

We see an ad for liquid rubber on TV that seals but remains pliant. Anyone have any experience with this material? Does it have any possibilities?

Once a rubber compound dries to its final state, the tension of the membrane becomes a factor. We have measured a number of of rubber based materials (silicone rubber, rubber cement, automotive undercoating, rubberized caulks, as well as white PVA emulsions/ie "Foamguard"), and they have all raised fs to unacceptable levels. The problem is compounded by the fact that the original sealant is still on the old surrounds.

It should be noted that toluene will often serve to soften the original KLH and AR treatments.

Roy

 

[gbroot]

I re-doped my KLH-5s using, on Merrylander's recommendation, rubber cement, which I haven't seen recommended anywhere else. But it seems to be a material that, though it dries, doesn't harden. My mistake, unfortunately, may have been using two coats (I tried to keep them thin), because I couldn't tell if I got good coverage on the first. The audible results are very similar to your description - louder, not as low, and with a peak.
I did this in conjunction with a recap, and have a post on the concurrent thread about cap break-in. My best hope is that someting will improve with use.

If you are unable to get it dissolved and decide to go the route of replacement, the Model 5's and 23's used the same woofers. There are usually a set or two for sale on the auction site.

 

[RoyC]

If you are unable to get it dissolved and decide to go the route of replacement, the Model 5's and 23's used the same woofers. There are usually a set or two for sale on the auction site.

Michael's craft stores sell "Heptane", which is a rubber cement solvent. It will remove it. (Btw,the rubber in rubber cement is a type of latex.)

Roy

 

[Treker]

IMHO opinion Roy Cs post really needs be a sticky, as this subject comes up at least 20 times a year, and people continue to put all kinds of stuff on surrounds without knowing the long-term consequences.

+1 on making this subject a sticky. It would have helped me immensely if an answer to this question had been readily available when I first started researching this subject back a few weeks ago. I'm just glad that I was able to locate the proper doping material before putting the inappropriate material on my cloth surrounds that may have been difficult if not impossible to remove.

 

[67 grad]

Michael's craft stores sell "Heptane", which is a rubber cement solvent. It will remove it. (Btw,the rubber in rubber cement is a type of latex.)

Roy

I know there is a rubber cement "thinner" but wasn't sure it would dissolve dried rc. The heptane sounds like a good bet.
I read a lot about re-doping before I did it, but still didn't realize just how critical the surrounds are in the AS design. That's a big Duh! thanks all for the tips.

 

[67 grad]

Ok - with all the posts on redoping KLHs I think I've only seen the midranges mentioned once. Does anyone know what those surrounds are made of? It looks like tissue paper.

 

[Ken Boyd]

I don't want to derail this thread, but found it quite interesting as I have been wondering where to find some black dope for some midrange domes. They are used on the Infinity's QLS lineup, its a soft fabric dome with a sticky black dope. With time that black dope seems to disappear allowing you to see thru it. I would bet that the dope recommended by Roy is the same thing or close to it.
I think I will order a batch to check it out.

On to the thread, since a source for redoping he drivers has been posted, and it seems very reasonable, why would anyone want to try something else and take a gamble? Its not like the stuff is 100 dollars a bottle, I wouldn't even try anything else once I was given a source which has been tested and found to be a good product, unless it was insanely expensive, which in this case its not.

 

[RoyC]

I don't want to derail this thread, but found it quite interesting as I have been wondering where to find some black dope for some midrange domes. They are used on the Infinity's QLS lineup, its a soft fabric dome with a sticky black dope. With time that black dope seems to disappear allowing you to see thru it. I would bet that the dope recommended by Roy is the same thing or close to it.
I think I will order a batch to check it out.

On to the thread, since a source for redoping he drivers has been posted, and it seems very reasonable, why would anyone want to try something else and take a gamble? Its not like the stuff is 100 dollars a bottle, I wouldn't even try anything else once I was given a source which has been tested and found to be a good product, unless it was insanely expensive, which in this case its not.

Ken,

According to Tom Tyson over at CSP (and our connection to Roy Allison) AR added lampblack to the solution. I have experimented with a similar black colorant, and it seems to work out OK. Larry has it available on request. It should be noted that the sealant can be removed with Goo Gone or toluene.

Roy

 

[mr.jones]

Thanks for the tip on the "Vintage AR" product....looks like it is defimitely worth the price.

 

[cuthien]

I am glad to find this article. I have a pair of vintage no name 10" woofers that has cloth surround and one of the woofer is very stiff. When i push down on the woofer, it hardly moves up/down (while the other one goes up/down easily). Do i simply buy the CLOTH SURROUND WOOFERS SEALANT kit on ebay and apply that chemical to the surround to my woofer or should i use "Heptane" first to remove whatever stuff that make the surround dried then apply the sealant. Thanks.

 

[RoyC]

I am glad to find this article. I have a pair of vintage no name 10" woofers that has cloth surround and one of the woofer is very stiff. When i push down on the woofer, it hardly moves up/down (while the other one goes up/down easily). Do i simply buy the CLOTH SURROUND WOOFERS SEALANT kit on ebay and apply that chemical to the surround to my woofer or should i use "Heptane" first to remove whatever stuff that make the surround dried then apply the sealant. Thanks.

No...There could be other reasons your woofer is not functioning properly. Even if it has something to do with a surround treatment, "heptane" was only suggested as a possible solution for a surround previously coated with rubber cement.

The sealant's primary function is not to loosen surrounds which have already lost compliance.

Roy

 

[cuthien]

thanks Roy for the respond. My speaker still work just fine even though it is stiff. I've cleaned the surround with alcohol but it's still stiff. Strange!