Aug 15th, 2018
The butyl used for textile surround restoring that has been recommended online appears to be somewhat problematic. First being that it is sticky, too sticky in my opinion – it’s attracting debris of any kind and accumulating on the surround. Large debris might actually cause some buzzing when vibrated. Another issue is the butyl treatment if allowed to get on the edge of textile where the cone is glued to the textile or the frame is glued to the textile appears to be dissolving the original glue at paper cone to textile and loosening it or causing separation. We have now seen this on a number of woofers treated this way, perhaps the seller should adjust this formulation somewhat or correct and careful application technique should be noted. Personally, I have not used this butyl service on our repairs. I worked for KLH and HH Scott and we knew at the time that these butyls were a little bit troublesome to mix up correctly and consistently. At my shop for 30 years we have used a special thinned out RTV silicon rubber, it works better and has less noise. Also, this treatment never ages out, it never soaks or drips to another area (butyl was notorious to slow creep to lower parts of surrounds), and it looks good – it never accumulates debris! Moreover, the special prepared silicon can be adjusted for thickness for the type of surround and most importantly it can better secure the centering of cone position for both height and center of the voice coil, which is another crucial issue that is seldom discussed. The fact is – and please no debates here – virtually all older woofers (and some mid range) need to have the voice coil properly centered axis and equivalent overhang of voice coil in magnet gap – before refoaming. In other words the spider must be brought back to level as accurately as possible so that the cone has equal swing out and inward. I will state emphatically right here, most if not all consumers who put on new surrounds will not get this correct. We redo so many home done refoams it’s alarming. An off center voice coil has an easy possibility of rubbing the enameled copper wire coating causing shorts as it scrapes the magnet gap and then suddenly this amplifier may fail or trip its protection circuit, for what appears to be just modest sound level being reproduced with a slightly miscentered voice coil. This is a non linearity in woofer motion – raising the harmonic distortion dramatically and lessening the speakers total output level and low frequencies. The effects can be subtle to the average listener, but when the speaker is corrected everyone notices a bass clarity and better sense of impulse on transients. Most people are happy if they think that they have fun fixing their speaker problem themselves, but the truth is the re-edge for a woofer is actually more difficult to truly do it correctly and properly restore an excellent spec KLH, ADS, Advent, Scott etc to it’s truly correct performance. Sorry, I can’t believe 90% of people who say they did a refoam right , I can only tell 90% of the people who show up here with their re-edged speaker damaged and their amp failed because they did it wrong. Thanks, Vince
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