Carlspeak Posted March 22, 2015 Report Share Posted March 22, 2015 Many of the popular model E and J models had the 8 inch Vifa M21WN-07 woofer. The original foam is very supple and had a large roll. What I discovered recently was a small bead of a non-hardening polymer was applied to the crease where the inner side of roll meets the angle attach area. I can only speculate what this was for, but think it might have been a way to dampen cone break up modes at high frequencies in the 1-5 kHz range.This filling in with the polymer in the crease reminds me of the filleted foam Boston Acoustics (and others) foam are known for. Perhaps the same reasoning could be applied there.Anyone have any thoughts on this. Check your Snells foams (if original) for this clear bead of polymer. Quote Link to comment Share on other sites More sharing options...
ra.ra Posted March 23, 2015 Report Share Posted March 23, 2015 Carl, I'm not terribly familiar with Snell, but does it look anything like this? This is the universal 8" AR replacement woofer that I have in my AR-7's. The original drawings for several 8" AR woofers show an applied substance in this area and simply call it "treatment". This issue was mentioned in this thread but did not receive any specific response. http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7897 Quote Link to comment Share on other sites More sharing options...
Carlspeak Posted March 23, 2015 Author Report Share Posted March 23, 2015 Interesting rara. The 'plot' thickens! Perhaps TT or Roy C could contribute. I wasn't aware some of the AR woofers had this. I was aware that some AR woofers had an application of something that extended down the slope of the angle attach portion of the surround and also onto the cone itself, but always thought it was just a generous application of a sealant at the inner edge of the surround. When doing refoams of these woofers I always found it convenient to peel the inner portion of the surround off with the aid of that 'treatment'. Quote Link to comment Share on other sites More sharing options...
Carlspeak Posted March 25, 2015 Author Report Share Posted March 25, 2015 It appears my theory regarding the purpose of the bead of polymer has been confirmed. I asked the question of the folks at AudioNote in the UK about the presence of the bead on original Snell E and J foams and the response was its purpose was to "help terminate the standing wave in the cone". To me, the last 5 words are another way of describing cone breakup modes. They create frequency response peaks above 1 kHz that are sometimes difficult to surpress with typical woofer LP crossover topologies. AudioNote has basically adopted the continuance of the Model E design but in a very high end version. They also sell replacement foams for the original E and J Vifa drivers, but they are quite expensive.In one case I am aware of, the Spica TC-50 and 50i, Jon Bau designed a special circuit that effectively tuned out those response peaks in the original 5 inch Polydax bass/mids but led to unique driver matching and service codes which described the character of the peak. I was told by AudioNote I could use a PVA wood glue type of adhesive for application to create a bead on new, refoams. However, application by hand will be difficult to produce a neat job. The originals were clearly done by machine. Quote Link to comment Share on other sites More sharing options...
RoyC Posted April 3, 2015 Report Share Posted April 3, 2015 Carl and ra.ra,Just happened to see this thread. I'm willing to bet the "filled fillet" Boston Acoustic foam serves the same purpose. It adds extra foam instead of glue to the edge, and fills in the crease. Roy Quote Link to comment Share on other sites More sharing options...
Carlspeak Posted April 3, 2015 Author Report Share Posted April 3, 2015 If I ever get an extra Snell 8 inch Vifa bass/mid to play with, I'll try a refoam, test FR and then add the fillet by hand ( ) and retest to see what the effect was on FR above 1 kHz. Quote Link to comment Share on other sites More sharing options...
RoyC Posted April 3, 2015 Report Share Posted April 3, 2015 If I ever get an extra Snell 8 inch Vifa bass/mid to play with, I'll try a refoam, test FR and then add the fillet by hand ( ) and retest to see what the effect was on FR above 1 kHz.Ah, you are a patient man, Carl. I will be very interested in your findings.Roy Quote Link to comment Share on other sites More sharing options...
Carlspeak Posted April 3, 2015 Author Report Share Posted April 3, 2015 Ah, you are a patient man, Carl. I will be very interested in your findings.RoyIt's the Sigma Xi in me that drives me to experiment with stuff! Quote Link to comment Share on other sites More sharing options...
Lazer Posted March 8, 2020 Report Share Posted March 8, 2020 I’m in the process of a reform on the VIFAs in my Snell Eiii and will hand lay the wood glue (per AN suggestion) with a pinstriping brush. You know, for perfect application. Quote Link to comment Share on other sites More sharing options...
ra.ra Posted March 9, 2020 Report Share Posted March 9, 2020 3 hours ago, Lazer said: I’m in the process of a reform on the VIFAs in my Snell Eiii and will hand lay the wood glue (per AN suggestion) with a pinstriping brush Hi Lazer and welcome aboard. I am not familiar with this woofer, so you may wish to post some pics for better description. If you'll note in Carl's original post, he mentions a non-hardening polymer, so I would think wood glue (which hardens) is among the last substances you'd want to apply over a foam surround. The substance shown on the AR woofer in the second post was very soft and pliable after 30+ years, and it felt very much like cured rubber cement. Quote Link to comment Share on other sites More sharing options...
daque13 Posted May 18, 2021 Report Share Posted May 18, 2021 From what I understand Carlspeak is no longer with us, but I sure would appreciate some photos to illustrate what is being discussed in this thread... Quote Link to comment Share on other sites More sharing options...
VSAT88 Posted November 5, 2021 Report Share Posted November 5, 2021 @daque13 the foam on those woofers are not any standard size. Those speakers are made in Denmark best I recall, in Europe anyhow. This is where I source ALL of my euro speaker surrounds and such. Very nice folks. Reasonable prices. Not Affiliated . https://audiofriends.eu/ Quote Link to comment Share on other sites More sharing options...
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