Guest Posted September 15, 2002 Report Share Posted September 15, 2002 Does anyone have any experience with using RTV silicone rubber for treating cloth surround? I am restoring a pair of AR-2ax with cloth surround. It had some sort of black coating on it but had fallen off over time. I remembered someone had mentioned using RTV with good result. And someone mentined "butyl latex". What is this RTV and butyl latex? Does it come in different form and brand name? It is water based or solvent based? How does RTV compare with butyl latex? Where can I buy RTV or butyl latex for my application? Anyone? Thanks for your help. Link to comment Share on other sites More sharing options...
kkantor Posted September 16, 2002 Report Share Posted September 16, 2002 Truth is, there is no way to really do this perfectly, but several ways to do it adequately. Personally, I would use Loctite "Black Rubber Sealant" rather than silicone ("RTV") adhesive. Most hardware stores have it. -k Link to comment Share on other sites More sharing options...
tysontom Posted September 17, 2002 Report Share Posted September 17, 2002 >Does anyone have any experience with using RTV silicone >rubber for treating cloth surround? I am restoring a pair >of AR-2ax with cloth surround. It had some sort of black >coating on it but had fallen off over time. I remembered >someone had mentioned using RTV with good result. And >someone mentined "butyl latex". What is this RTV and butyl >latex? Does it come in different form and brand name? It >is water based or solvent based? How does RTV compare with >butyl latex? Where can I buy RTV or butyl latex for my >application? Anyone? Thanks for your help. Early on I think that Acoustic Research used a butyl-rubber compound on the cloth surrounds, but I don't think it was a latex-rubber version at that time. By the time of the foam surrounds, AR and others began using butyl-latex, for example the Airflex 400 and Lord Corporation BL-100 type butyl-latex. It was a white liquid (similar to Elmers Glue or Carpenters Glue but with different properties) that dried clear, or in some cases was mixed with lamp black to dry black. Finding that commercial liquid is easier said than done. Ken's idea of using Loctite rubber sealant would most likely be the best idea for the cloth surrounds.If the original cloth surround is not badly deteriorated, I have also found that applying (with small paint brush) several coats of Armoral Vinyl and Rubber Protectant (auto-supply stores) will restore the original qualitites of some cloth surrounds. but the original can't be completely deteriorated. --Tom Tyson Link to comment Share on other sites More sharing options...
Guest Posted September 17, 2002 Report Share Posted September 17, 2002 Dear Tom and kkantor,Many thanks for your inputs. The cloth surround is still in good condition. The purpose of coating is to seal it to make it air tight. Do Loctite "Black Rubber Sealant" and Armoral Vinyl and Rubber Protectant work for this purpose? I have a pair of Marantz Model 7, the 12 inch woofer has cloth surround and coated with a sticky black material. It is over 20 years old and the coating and surround are still in excellent condition. This is the kind of material I am looking for. Also, on new foam surround, would the coating protect it from rotting? The coating should not affect the compliance or make it too stiff, otherwise the sound could be altered.Lord BL-100 suggests that coating the speaker cone with it. They claim it improve sound quality. Any thought about this? Link to comment Share on other sites More sharing options...
tysontom Posted September 17, 2002 Report Share Posted September 17, 2002 >Dear Tom and kkantor, >>Many thanks for your inputs. The cloth surround is still in >good condition. The purpose of coating is to seal it to >make it air tight. Do Loctite "Black Rubber Sealant" and >Armoral Vinyl and Rubber Protectant work for this purpose? The purpose is not to make the cabinet completely air-tight as in a hermetic seal. Then the woofer cone would act like an aneroid barometer and not stay centered. The purpose is to make an "acoustic seal" of the cabinet; i.e., sealed sufficiently that the cabinet gives the cone the 75-90% elastic-restoring force. Therefore, even a little air leak is not going to be detrimental to proper performance so long as the cone gets proper restoring force at its lowest frequencies. If you gently push in the woofer cone (mounted in the acoustic-suspension cabinet) with your fingers centered around the dust cap, and release, the cone should slowly return as though it is passing through a viscous fluid. A relatively slow return to the "center" position is nearly always sufficient to acoustically seal the woofer for the audio frequencies it is intended to reproduce. If the woofer snaps back out immediately, then the woofer is not properly sealed. You can also time it to be sure that the cone returns not faster than the time for one-half cycle of the lowest frequency you wish to reproduce, but that is really over-kill.>Also, on new foam surround, would the coating >protect it from rotting? The coating should not affect the >compliance or make it too stiff, otherwise the sound could >be altered. >Once the oxidation begins, I think that coating will not prevent the inevitable but only slow its progress. You would have to coat the foam on both sides, and then it will still degrade over time and only be held together by the coating. But with new surrounds, you may get quite old before the real deterioration begins.>Lord BL-100 suggests that coating the speaker cone with it. >They claim it improve sound quality. Any thought about >this? If you coat the cone, you might alter the properties of the driver by adding weight to it. Probably a light coat would not do much, depending on the mass of the cone to start with, but it probably would not help as much as hurt the cone in the end. Roy Allison coated his drivers with butyl-rubber (same as the BL-100), but he took into account any changes and such that might come from it. It improved suppression of standing waves and such.Kkantor would know a great deal about this subject, since he was (and still is) a respected and very successful speaker engineer.--Tom Tyson Link to comment Share on other sites More sharing options...
kkantor Posted September 20, 2002 Report Share Posted September 20, 2002 Tom is too kind! (I'll tell you after the next CES if "was" or "still is" is the operative term...)The Lord products can sometimes be very useful to people who design and build speakers. In this case, their effects are known, and worked into the design of the driver.I'm less positive about applying them after the fact. Speaker design is a moderately complicated thing. Many performance factors are interwoven and interdependent. Cone mass and surround shape and glue type and stuffing density and crossover values, on and on. Assuming the original design is done by a skillful and patient engineer, it all comes together in a certain way, and you like it or you don't. When you start to mess around with one thing, like adding material to the cone, or changing caps in the crossover, you need to think holistically. You might fix one thing and break another. For example, adding a thick layer of the Lord material might well reduce midrange breakup. It will also make the cone heavier, thus upsetting the bass tuning and the midrange crossover point. You might or might not like the results. If you hate the speaker and think almost any change will help, go for it. If you like the speaker and are trying to inch it forward in performance, you are taking a big risk. Ken KantorIntelligent Audio Systems, Inc. Link to comment Share on other sites More sharing options...
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