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Old 8th October 2011, 09:50 PM   #1
elecrto is offline elecrto  United States
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Default How to fix & recondition a vintage paper cone?

I have a vintage EV TRX that is beginning to crack around the edge from the paper being so dry and fragile. These drivers do not have the typical accordion surround but have a formed paper cone, edge to edge. I've read a bunch of different ideas on how to fix this, but there seems to be no consensus on the right way and what products to use. The critical step appears to be creating a solution that can penetrate the paper and not sit on top (ArmorAll not a good idea) I read an interesting article on how to repair paper documents by making a starch based adhesive.

Northeast Document Conservation Center —*Repairing Paper Artifacts

Would the enABL coating process possibly help with this issue? I would love to hear from anyone who have actually found a process that works without negative effects to the driver.
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Old 12th October 2011, 04:18 AM   #2
Illusus is offline Illusus  Canada
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I'm starting a similar project. I'm on the last leg of restoring a 1948 Gibson GA50-T guitar amp. It started out as a mouse poop container church find but is looking pretty damn sexy now with most of its electronics replaced and cabinet refurbished.The last step is repairing one of the speakers, an 8", Jensen "Alnico 5 Concert Series" driver (P8-R-ish). A few sections of the cone separated at the periphery where it meets the basket. There is no surround, or rather it is integrated into the cone shape. I am planning on mulching up an old cone from a similar speaker that seems to be made of the same paper and mixing the fibers with Mod-Podge/PVA glue and water to make a pulp to use as a patch. I'm making it up as I go along, it makes sense to me, but then again I'm not too bright. I hope I don't make it worse. I'll probably coat the entire cone and the cone of the larger 12" version, that shares cabinet space with the 8", in mod podge to give them lasting strength. I always practice new techniques on junk parts first so I should have an idea of the potential for success tomorrow or day after. i will keep you posted. Does anybody else here have experience in this field to share?
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Old 12th October 2011, 07:58 AM   #3
freddi is offline freddi  United States
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fwiw a kid on Youtube uses clear silicone (vicosity/etc. not specified) -
How to prevent vibration fatique in vintage speakers. - YouTube
I'm not sure how well that would permeate a paper surround - maybe planet10 has some wisdom to share
(my 1960's Karlson X15 hads CTS 15" with paper surround which could use rejuvenation/protection)

Last edited by freddi; 12th October 2011 at 08:01 AM.
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Old 13th October 2011, 12:58 AM   #4
elecrto is offline elecrto  United States
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I went ahead and tried using a pva glue. My first pass was a 50/50 mix of water and glue. I only attempted the surround since it was the only area that needed repaired. I coat on top 1 coat on the bottom. The glue did absorb into the paper but when dry it did not fill/hold the tear together. Also as it dried there is a little shrinkage that occurs that began cracking farther around the cone. The next application was a 100% glue. This seemed to work better for a tear because it could sit on top of the cone and the thickness of the glue held the paper together. The other benefit was it did not soak the paper creating a shrinking effect. All in all it is an ok fix for tears but I would recommend trying something else for conditioning the paper. The paper is now fairly stiff, probably too much glue, and maybe too stiff for a surround. I could not tell you how the performance has changed since I did not use the speaker prior to the fix in fear of the surround completely cracking. However, the cone barely moved prior to the treatment, since it is 1 piece of formed paper with minimal flexibility. I'm debating cutting off the surround and replacing it with a newer accordion style. Never done it before, so it could be an interesting experiment. I've read the TRX with the accordion surround sounds better anyway. As is the speaker is pretty impressive on open baffle with a helper woofer. Does anybody have another they want to sell me so I can listen in stereo
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Old 14th October 2011, 04:43 AM   #5
Illusus is offline Illusus  Canada
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I aborted the pulp project due to time constraints. The restoration has to be complete this weekend and I didn't want to eat up my time experimenting with a new method so I resorted to something simpler. I cut out a new "surround" from a coffee filter and glued it over the existing, torn surround. I used 50/50 mixture of Mod-Podge and water. The wet coffee filter paper was very easy to apply as it conformed to the shape of the original surround almost automatically. I also used the Mod-Podge to coat the entire cone, a tried and true method of planet10 for coating paper cone drivers. I used to use dammar for this purpose until I finally tried Dave's method and was instantly sold.
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Old 20th January 2012, 07:29 PM   #6
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Quote:
Originally Posted by elecrto View Post
I have a vintage EV TRX that is beginning to crack around the edge from the paper being so dry and fragile. These drivers do not have the typical accordion surround but have a formed paper cone, edge to edge. I've read a bunch of different ideas on how to fix this, but there seems to be no consensus on the right way and what products to use. The critical step appears to be creating a solution that can penetrate the paper and not sit on top (ArmorAll not a good idea) I read an interesting article on how to repair paper documents by making a starch based adhesive.

Northeast Document Conservation Center —*Repairing Paper Artifacts

Would the enABL coating process possibly help with this issue? I would love to hear from anyone who have actually found a process that works without negative effects to the driver.
The goo Altec uses on their driver surrounds looks promising as does the sealer used by EV on thier cloth surrounds. I was thinking japanese tissue on the back side with the EV surround sealer. Should add very little weight, maybe put back what has dry rotted away and still remain as flexible as originally designed. The Altec goo may add too much weight. I would not coat the entire cone with anything, it will add weight and with the whizzer already adding weight you don't want any more. The TRX is a good driver capable of reproducing up to 8000 hz even though the crossover for the tweeter is 3500 hz. Add weight to the cone and you will not get the extended response.
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Old 21st January 2012, 01:50 AM   #7
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Default surround repair

Please don't use white glue on your surround. Too stiff. I use clear urethane sealant thinned a little with water. Stays flexy, looks glossy, works every time. I really don't get the ModPodge deal, but as a woodworker I'm inclined to think there are more tools in the waterborne chest than what my art teacher wife has relied on all these years. Call me biased.
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Old 21st January 2012, 02:08 AM   #8
sreten is offline sreten  United Kingdom
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Hi,

PVA (wood glue) is good for fixing paper cone tears, use tissue to allow gaps
to be bridged if necessary. Water based contact rubber adhesive is best for
paper and foam surrounds I've found, easy on the front, not so much the rear.

rgds, sreten.
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Old 21st January 2012, 02:28 AM   #9
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I need to find out what EV uses for the surrounds. Seems that goo would be the best for treating the paper. The altec stuff stays tacky forever but looks heavy.
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