Surround Dope

[potatofarmer]

I've found a bunch of threads, here and elsewhere, about what to use for doping the surround on a DIY recone. PVA (white) glue, rubber cement, contact cement, vinyl dissolved in toluene, various dilutions of the above... It's starting to drive me nuts.

Mr. Fahey has been a huge help with his posts over the years, but there have been some contradictory posts about the acceptability of PVA.

What I've been able to piece together is that you want an elastic compound (butyl rubber in the case of cloth surrounds) in a solvent base selected to penetrate the paper well, carry the solute load into the paper, and have a decent working time.

I'm experimenting with DIY reconing using a pair of Utah C12N-like drivers with rotted cones. Apart from using a spider that's too tall, it's been going OK so far. Nowhere near the quality of a new speaker, but turning junk into something useable for $20 isn't bad.

I was planning on using a thinned PVA - my wife has a bottle of Mod Podge, and it dries to an elastic film. But then I started doing more research and started looking into various rubber-based adhesives, when I found this stuff called Tear Repair, and it appears to just be a thin latex solution in water & ammonia.

Without additional dilution, most of the solid stays on the surface of the cone (practicing on a rotted one), though some does appear to penetrate. The dried latex rubber can be peeled off.

Diluting with water seems to not yield much improvement; I'll try diluting with water and ammonia. I'm a little worried that this might just be a waste of time as I don't think subsequent coats will dissolve a dried one.

In any event, does anyone have a suggestion for what I should do here? Give up on latex rubber and go with something in an organic base? Use thinned PVA and stop over-thinking this?

[potatofarmer]

Perhaps unsurprisingly, the front of the cone soaks up dope a little differently than the back of the cone. The "Tear Mender" / liquid latex seems like a decent one-coat solution for PA drivers. Nice and wet looking, dries translucent, and remains sticky. I think I'll give this stuff a shot, and if I don't like the result I'll use thinned PVA on the other Utah that I've got to recone.

[pdf64]

Some info on doping from JMF here Does doping affect speaker (cone) breakup characteristics? | The Gear Page

[potatofarmer]

Some info on doping from JMF here Does doping affect speaker (cone) breakup characteristics? | The Gear Page

Oh yeah, I've read it. JM Fahey has been a huge resource on this topic. He goes into a little more depth here: http://music-electronics-forum.com/t39504/

A lot more here: speaker doping | The Gear Page

Part of what drives me crazy about this stuff is how secretive it all is. You can't buy cones/coils/spiders unless you're a recone shop (except the few offerings Weber has), the glues are all specialized, and absolutely no one on the internet seems to know what, exactly, is used to dope paper surrounds. The whole thing is kind of hilarious as there can't be much money in the recone business.

Personally I think a better way to protect the reconing business is to just let everyone have the parts and glues and whatnot and let them try it once. I bet 75% of people would give up halfway through trying to clean the basket and the rest would have lousy results from trying to use the wrong parts.

Makes me tempted to open a recone business, if only on paper, just to get the keys to the kingdom. I'm already going bonkers over bass cab design, might as well go all in with reference mics and impedance sweeps and oh my yes...

[potatofarmer]

While I'm at it, if anyone can recommend any books on loudspeaker design and construction, I'd appreciate it. I've already read Vance Dickason's Loudspeaker Design Cookbook and found it of limited use. More of a higher-level philosophy text than a technician-level "actually building the things" text. Which has its place, sure, but it's of limited utility if you don't have a shop full of people you can dictate your requested specs to.

[gbono]

While I'm at it, if anyone can recommend any books on loudspeaker design and construction, I'd appreciate it. I've already read Vance Dickason's Loudspeaker Design Cookbook and found it of limited use. More of a higher-level philosophy text than a technician-level "actually building the things" text. Which has its place, sure, but it's of limited utility if you don't have a shop full of people you can dictate your requested specs to.

here is a link to the Loctite products http://www.loctite.ph/php/content_da...ives_Guide.pdf

Speaker design and assembly isn't a black art but it sure is hard to find any resources beyond working in the industry and getting hands on experience though most of this work is going on overseas (Asia, Europe, etc). I think you hit the nail on the head about 75% of the users wouldn't attempt another recone after one project so this isn't a very large industry and therefore parts and knowledge are scarce or restricted. Reminds me of the automotive "body and fender" industry though all the paintless dent repair technology is really fascinating.

[gearhead63]

I have purchased some of the black rubberized doping from Springfield Speaker Repair on eBay.
GREAT stuff! It looks exactly like what Celestion uses. I've used it to do minor cone repairs
replacing loose dust caps and to dope the surround/edges of some speakers.
It's $14 with free shipping for a 2oz. bottle.
They sell larger and smaller quantities.
Go to eBay and search for item # 290506089935

[potatofarmer]

I've been doing a little more research. The Springfield Speaker Repair dope looks interesting, but the cost seems high. I'm thinking there's a cheaper source - trying to figure out what they buy and slap their label on. I worked in a swimming pool supply store for one lousy summer and it's amazing the markup you can get by adding a few words to a description. O-rings are cheap, "swimming pool pump" o-rings are expensive. Glue is cheap, "speaker" glue is expensive.

One thing I've found out so far is that not all PVA glues are the same; there are additives to modify the performance, resilience to UV light, flexibility, tackiness, and so on.

More interestingly, there are other "water-based vinyl acetate" adhesives besides the usual PVA - namely, EVA; "ethlyene vinyl acetate" in a cold emulsion. It's used in bookbinding and isn't recommended for woodwork since it remains so flexible. Aha!

I haven't found many commonly-available EVA glues yet. So far just "Helmar Super Tac Glue" which is available on Amazon. Looks like Helmar makes some other promising adhesives too.

Oh and the "Tear Mender" liquid latex does in fact peel off rather easily without any noticeable wetting of the actual paper. Dilution just leads to the solids clumping, which might be improved by adding a little ammonia although it's not really worth looking into further. If you want to add some mass or make a surround look really nice, it's probably a good choice though.

Here are some links, mostly posting so I don't forget them:
https://aiccm.org.au/sites/default/f...l17No1and2.pdf
DIY HARDWARE : Super Tac EVA 8.45 fl.oz.

[gearhead63]

potatofarmer, the glue from springfield is not a water based glue. I believe it had acetone in it that evaporates and leaves the rubberized material on the surface.
I looked and couldnt find but one other source. Good luck.

[olddawg]

The old classic "sales floor" repair for a torn cone was single plies of toilet tissue layed up using clear fingernail polish. Then a little flat black spray paint to blend in the repair. Lol. Ive seen such repairs last decades.

[Zipslack]

The old classic "sales floor" repair for a torn cone was single plies of toilet tissue layed up using clear fingernail polish. Then a little flat black spray paint to blend in the repair. Lol. Ive seen such repairs last decades.

That there is fancy work...fingernail polish! Here in the poor part of the woods, we use Elmer's glue diluted with water.

[potatofarmer]

potatofarmer, the glue from springfield is not a water based glue. I believe it had acetone in it that evaporates and leaves the rubberized material on the surface.
I looked and couldnt find but one other source. Good luck.

Yeah, the black rubberized glue (inner tubes dissolved in hexane?) they sell isn't water-based, but the stuff they sell for surround damping is. I'm tempted to try that, but I'm skeptical that the solids would penetrate much into the paper. That rubberized glue would probably be great in cloth surrounds though...

Hm, I reread your original post. I should check out a Celestion. Actually, I should double check all my speakers and compare the dope; I've been trying to match the translucent shiny kind that doesn't stay tacky.

I do have a second recone almost ready for doping, might just try them both...

[gearhead63]

The Springfield glue is great stuff. It looks and feels EXACTLY like the doping that is on my Celestion G12T75 and G12H100 speakers.
I used some on an older G12K85 that the edge was getting flaky on. It didn't originally come with doping.
I tried it and have been using that speaker in a 2x12 cab with a vintage 30 for about 3 years and no problems.
It stiffened the cone around the out side a little and helped take the flubbiness out of the bottom end.
I've used it also to repair puncture wounds in a couple black widows I have.
It's costs a bit, but goes a ways. I used a flux brush to spread it out after i squeezed a small line of glue out.
The only drawback is that once opened, it doesn't have a long shelf life. So only buy what you think you can use in a short time.
You won't be disappointed.

[potatofarmer]

Yeah, that's probably the easiest and best answer. I'm just a nutjob.

Here's a good thread of some hi-fi folks going crazy over what to use for cloth surrounds: Using Latex Cement for KLH Cloth Surround Doping | Audiokarma Home Audio Stereo Discussion Forums

Also, I found this today: Surround Adhesives

Just going off their descriptions:
WHITE LATEX ADHESIVE DAMPENER -> probably the same as "Tear Mender", "liquid latex" - latex in water, stabilized with ammonia
BLACK & YELLOW HEAVY DUTY ADHESIVES -> I suspect these are essentially "contact cement" e.g. neoprene in hexane
BLACK DOME GLUE -> Rubber cement (latex in hexane) with black pigment? Butyl instead of latex? This is probably similar to what Springfield is selling.
#WDT CLEAR TACKY SURROUND DAMPENER ADHESIVE -> This sounds a lot like a water-based EVA glue
#BD BLACK LATEX ADHESIVE DAMPENER -> Liquid latex with black pigment? Long dry time (and a similar description) makes me think water based.

I have no idea why I've gotten so obsessed with this. I swear I'm not ignoring your advice, I just have more time than sense (or cents).

[potatofarmer]

Helmar Super-Tac seems like a good choice for something water-based. One coat of full-strength is probably sufficient. Thinned 1:1 with water seems to penetrate paper really well. It's pretty runny though, and the first coat seals the surface rather well so running might be an issue. I'm thinking one coat thinned followed by a coat at full strength.

It does seem to help resist tearing, but doesn't seem to penetrate much into the paper. Which makes sense because, well, it's paper! Whatever Utah used back in the day behaves roughly the same.

It does dry slightly milky, but it's only noticeable with thicker coats (2+ at full strength). I'm drying some on a piece of glass to see how flexible it remains. According to bookbinders and scrapbookers everywhere, it should remain permanently flexible, and some EVA emulsion adhesives are re-dissolvable in water after they've set.

On the butyl front, there are butyl-based caulks available but they have a lot of solids (sand, salts, etc) and supposedly get stiff after a couple months.

Windshield adhesive, however, seems more promising. It's available in pint cans and caulk tubes, with the caulk tubes costing about half of what the can does. The manufacturer strongly recommends against trying to thin it. More updates when I've tracked a tube down...

Edit: the stuff I found is CRL-7708.