brownrock Posted October 27, 2019 Report Share Posted October 27, 2019 Hello to all, So far I've have been happy just reading all the knowledgeable things people here have to say but now I have a question of my own I would like answered (which may or may not already be answered elsewhere here - in which case hopefully someone will be kind enough to direct me accordingly). I have a pair of Mission 720s which I have owned from day 1 (I purchased them in 1980). I have used them more or less continuously all these years. The mid range surrounds (the mid range as I understand it are Peerless K040-MRF) are separating / coming apart in a couple of places on the outer edge (pic below with lines on either sides of the split surrounds). I have more pics I can post if anyone wants to see more of what I'm talking about. This is affecting the sound quality. I am considering replacing the existing surrounds which are fabic (silk???) with foam surrounds BUT after reading many of the comments on this site it occurs to me that there may be some way to repair the damage (Permatex on the split, maybe) and keep the original surrounds which 'appear' to be in otherwise reasonable condition. Your thoughts and suggestions would be very welcome. Many thanks to you for taking the time to read this post and possibly answer my question. Quote Link to comment Share on other sites More sharing options...
DavidR Posted October 27, 2019 Report Share Posted October 27, 2019 Replacement surrounds: https://www.ebay.com/c/2108592833 Perhaps cloth are available thru another vendor. Quote Link to comment Share on other sites More sharing options...
brownrock Posted October 27, 2019 Author Report Share Posted October 27, 2019 Many thanks David, Foe anyone looking for foam surrounds there are a few suppliers. The one that seems to stand out ahead of the others is one called AudioFriends out of Holland. Here's a link to the item - https://www.repairyourspeakers.com/en/foam-surrounds/other-manufactures/peerless/peerless-k040-mrf-821385-midrange-repair-foam-surround/a-2278-20000060. As far as the link you provided the seller claims to sell surrounds but when you follow the link they are just selling a pair of old Kenwoods. Not sure what their deal is. At this point and having ready a substantial number of posts / comments here (and elsewhere) I would really like to try to save the existing cloth surrounds by repairing them. Just not sure whether this is just wishful thinking on my part, Thanks again for taking the time to read and answer my post. Quote Link to comment Share on other sites More sharing options...
DavidR Posted October 27, 2019 Report Share Posted October 27, 2019 I was unable to find any cloth surrounds on that driver - either pictures or suppliers. Quote Link to comment Share on other sites More sharing options...
GD70 Posted October 27, 2019 Report Share Posted October 27, 2019 You're going to need a very thin, light weave material, maybe silk, and butle rubber, or the sealer we use on AR and KLH surrounds to reseal them. The piece of fabric should extend at least a 1/4 inch past the tears. The butyl sealer should be applied sparingly, just enough to hold the patches in place. You don't want to put too much on and restrict the cone movement. I'd inspect the other mid as well as it could be in the same state or close to it. Good luck, Glenn Quote Link to comment Share on other sites More sharing options...
brownrock Posted October 27, 2019 Author Report Share Posted October 27, 2019 Thanks David, By the sounds of what different people say there's no one making cloth surrounds any more and no NOS. But, hey, I hope I'm wrong on that score. Finding new cloth surrounds would be great. Quote Link to comment Share on other sites More sharing options...
brownrock Posted October 27, 2019 Author Report Share Posted October 27, 2019 Thanks Glenn, You are confirming what I was hoping might be possible. Also I appreciate how specific your answer is. May I ask what sealer you use on AR and KLH? In your opinion (or better still experience) would such a repair substantially restore the surrounds to their original functionality OR will the sound quality be significantly altered / impaired due to the addition of new materials (fabric and rubber / sealant)? Quote Link to comment Share on other sites More sharing options...
ra.ra Posted October 27, 2019 Report Share Posted October 27, 2019 11 hours ago, brownrock said: I am considering replacing the existing surrounds which are fabric (silk???) with foam surrounds... Hi brownrock, and welcome to the CSP forum. (Just FYI in the future, threads such as this one should be posted in the "Other Speakers...." section rather than the Acoustic Research section.) Your photo is pretty good, but are you certain this is a fabric surround? To me that certainly looks like a foam surround - - not cloth - - and it appears to have deteriorated on those circumference edges which is a very typical location for aged and brittle foams. And even if they are cloth, this would be an extremely challenging repair given the size of the driver and the complex configuration of the location of those splits. New fabric surrounds are available, but they are not very common. My advice would be for new foams, as discussed in this thread. https://audiokarma.org/forums/index.php?threads/interesting-speakers-incoming-mission-720.817658/ Quote Link to comment Share on other sites More sharing options...
brownrock Posted October 27, 2019 Author Report Share Posted October 27, 2019 Thanks so much Ra.Ra, Much appreciate your thoughts and comments. #1 - I actually didn't realize I was posting in any particular section. Is there any way this post can be moved to the correct section? #2 - To be perfectly honest I don't know for a fact that these are fabric. I was going by what I have read here and there. Any number of people suggest that these surrounds are fabric but that's no proof of anything (is it ever!). They may well be foam, but if they are they don't look like the kind of foam surrounds you see these days. I've avoided touching the surrounds for fear of damaging them further. Is there any way I can delicately test to see if they are foam or fabric. The Mission manual of the times doesn't say anything on that subject. Thanks so much for the link. I'm there now. Looks spot on so far! Quote Link to comment Share on other sites More sharing options...
ra.ra Posted October 27, 2019 Report Share Posted October 27, 2019 #1 - Don't worry about this - - if it needs to be moved, the site moderators will take care of it. #2 - I don't know these Mission speakers at all, but none of my very limited reading suggested these were foam surrounds. With age, foam surrounds become dry and frail, and often crumble at just the slightest touch. A helpful tool to confirm surround material is a magnifier - - if cloth, you should be able to clearly see the weave of the fibers in the fabric, as in pic attached, which shows a small tear in the rolled portion of a 50-year old woofer. Quote Link to comment Share on other sites More sharing options...
brownrock Posted October 27, 2019 Author Report Share Posted October 27, 2019 Thanks again ra.ra, Attached is a close up and I would have to say that these are foam. I cannot make out any fibers in the surround material. Which is consistent with what was said on the post you linked to (above). So if these are foam surrounds (and not fabric as I stated earlier) would there be any merit to giving Glenn's suggestion? or is the idea of mating a silk patch to a foam surface a nonsense idea? here's a close up pic of the surround. Quote Link to comment Share on other sites More sharing options...
ra.ra Posted October 27, 2019 Report Share Posted October 27, 2019 Oops....I have corrected a small but important mistake in my earlier post. Re: patching solution, Glenn is an excellent restorer and a generous source of much information regarding various speaker models, but his suggestion was intended only for original cloth surrounds. Once a foam surround has degraded to this level, there is no "fix" that can restore its functionality short of a complete replacement. Quote Link to comment Share on other sites More sharing options...
brownrock Posted October 27, 2019 Author Report Share Posted October 27, 2019 ra.ra... Thank you ever so much for taking the time to answer my questions and musings. What you say makes sense and so I think that maybe my starting point was correct and that would be to order some foam surrounds from AudioFriends. From my research (albeit still somewhat limited) these AudioFriends surrounds appear to be the correct size and configuration ie. 'inverted'. https://www.repairyourspeakers.com/en/foam-surrounds/other-manufactures/peerless/peerless-k040-mrf-821385-midrange-repair-foam-surround/a-2278-20000060 Hopefully they will confirm that that these are the surrounds I need. Now I'm left with the question of whether I have what it takes to 'take on' the challenge of positioning the cone correctly. I've read about using shims but this sounds arduous especially that the cones are enclosed. But I also did read Glenn's post re: using a tone to position the cone. This sounds somewhat arduous but in a different way. Both ways do not appear to be the subject of extensive 'how to's' and that maybe the real challenge. I'm happy to take on even complex tasks (like replacing head gaskets) provided I have good instructions. So I guess I'm off to look for good instructions on how to position a cone in an enclosed` unit. Hopefully I'll find something I can use. Thanks again Quote Link to comment Share on other sites More sharing options...
DavidR Posted October 27, 2019 Report Share Posted October 27, 2019 When searching for the cloth surrounds I found a service that will do it for you. Would you like me to find and post it? Quote Link to comment Share on other sites More sharing options...
brownrock Posted October 27, 2019 Author Report Share Posted October 27, 2019 Thanks so much David. Turns out my surrounds are foam but posting the link to cloth surrounds might prove useful ... if not to me then to someone else with the challenge of finding them. So short answer: yes, please. And thanks for your support and help and contribution. Quote Link to comment Share on other sites More sharing options...
GD70 Posted October 28, 2019 Report Share Posted October 28, 2019 Foam surrounds are fairly easy to replace. Once all the old foam has been removed, there's usually some still stuck on the cone edges. I use a small plastic taping knife and carefully scrape away as much as possible. I keep my fingers under the cone for support as I gently scrape away the remaining foam. Usually there's also a bit of old glue remaining, which I rub off between my fingers. There will still be a little remaining which is fine. Youll also need to scrape all the remaining foam and glue off the basket surfaces so they are smooth. Upfront prep is important. Using shims is fool proof. I carefully cut the dust cap around the base close to where it's glued to the cone. I leave just a bit uncut and flip it up like a can lid. This makes it easy to realign the cap when regluing. Glue the new surrounds to the cones first. When dry, glue to the basket. Many use wood clothes pins to hold the glued surround edges in place while the glue dries. When dry, pull the shims, move the cone in and out to make sure there's no VC rub, reglue the dust cap in place and you're ready to hear your speakers sing! Glenn Quote Link to comment Share on other sites More sharing options...
brownrock Posted October 28, 2019 Author Report Share Posted October 28, 2019 Many thanks for that detailed 'how to' Glenn. You mentioned in one of your posts (somewhere else) that you had tried the tone method with good results. I think it was for a sub though. Do you think the tone method works equally for mids or is the tolerance too tight (probably a stupid way of formulating my question!)? I am given to understand that the tone to use is 1675 Hz? What about the battery method? Any thoughts? Quote Link to comment Share on other sites More sharing options...
DavidR Posted October 28, 2019 Report Share Posted October 28, 2019 I never found anything for cloth just foam. Here is one service > https://reconingspeakers.com/2011/11/07/peerless-k040-mrf-midrange-repair/ Quote Link to comment Share on other sites More sharing options...
brownrock Posted October 28, 2019 Author Report Share Posted October 28, 2019 Thanks David Quote Link to comment Share on other sites More sharing options...
GD70 Posted October 30, 2019 Report Share Posted October 30, 2019 On October 27, 2019 at 8:51 PM, brownrock said: Many thanks for that detailed 'how to' Glenn. You mentioned in one of your posts (somewhere else) that you had tried the tone method with good results. I think it was for a sub though. Do you think the tone method works equally for mids or is the tolerance too tight (probably a stupid way of formulating my question!)? I am given to understand that the tone to use is 1675 Hz? What about the battery method? Any thoughts? I used the tone method of a set of JBL 4301b woofers. Those woofers have big beautiful concave dust caps that I didn't want to cut. Worked perfectly. Quote Link to comment Share on other sites More sharing options...
brownrock Posted October 30, 2019 Author Report Share Posted October 30, 2019 thanks for taking the time to answer my question Glenn. Much appreciate your input. Quote Link to comment Share on other sites More sharing options...
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