Muslin or Fiberglass for wrapping audio speakers prior to paint

[andrew whicker]

Hi,

I've been given the idea of using Muslin or Fiberglass to wrap speakers I'm making to cover joints vs using something like Bondo before having them professionally painted. According to him (and I very much trust this person according to his experience), the best way to cover up glue lines for the longevity of the project is to use a cloth (i.e. heirloom). Apparently, Bondo will eventually show the glue lines.



Does anyone have experience with this using these fabrics in a vacuum table w/ epoxy? Maybe not using a vacuum table (I have one, but I'm open to NOT using it as well)? I talked to him about it, but I'm always up for listening to other people's experiences.

Cheers,

[Mel Fulks]

No,not with fiberglass. But I have posted several times about using “cotton duck” cloth glued on to wood or plywood , then primed and
painted. I use high quality exterior acrylic paint. Goes way back, but people don’t talk about it now’cuz they haven’t seen any of their
neighbors use it. The process is as good as “sign board” but cheaper . Long time ago they used the paint as the “glue” . I use Titebond 2
to glue the cloth to the plywood, and the edges.

[Bill Dufour]

In assume you mean speaker boxes not cones?
Bill D

[Mel Fulks]

Muslin is thinner and more stretchy than light canvas , which is also sold as “cotton duck”.

[Maurice Mcmurry]

I have a description of the process Mel describes in an old boatbuilding book. I will dust it off and see if anything could apply to speakers.

from Boatbuilding Manual Robert M. Steward (fair use)

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[Mel Fulks]

I would use the canvas.

[Jamie Buxton]

Cloth might be structurally sound, but I think you'll have a big challenge getting it to the point that the texture doesn't telegraph through the paint.

As to using a vacuum press to adhere anything to a hollow box, you're asking for trouble. The air pressure will collapse the box.

[Frank Pratt]

I wouldn't use any fabric. Too much work.

With a sander, slightly hollow (about 1/16") the area along the joint. Then use the glass reinforced Bondo to fill it. As long as the joint is sound, it well never telegraph through. I built a 20 cu ft subwoofer and used that method. It has a 1500 WRMS amp driving it and even with that sort of seismic violence going on there's not a hint of the joints.

[Maurice Mcmurry]

What about Phenolic Paper rather than fabric? I have some veneer with phenolic backing. Here is a source for thin sheets.

PAPER PHENOLIC - GRADE X - PAPER PHENOLIC - ORDER ONLINE (https://www.professionalplastics.com/PHENOLICPAPERX)

486429

[Mel Fulks]

Yes ,there will be some texture . Similar to the fake leather that has been used. I thought Andrew wanted texture…and still think that.
The cotton duck won’t have much texture. There are a number of canvas thicknesses , all available on line. When canvas is used just for
strength of the box, it can be filled with spackling to make surfaces completely smooth. I would thin Titebond 1 or 2 just a bit with water and
apply to both surfaces for the gluing. I would do one side at a time. One hour is enough to move on to the next side.

[Mel Fulks]

[QUOTE=Maurice Mcmurry;3214282]What about Phenolic Paper rather than fabric? I have some veneer with phenolic backing. Here is a source for thin sheets.

PAPER PHENOLIC - GRADE X - PAPER PHENOLIC - ORDER ONLINE (https://www.professionalplastics.com/PHENOLICPAPERX)

Sure, you can use phenolic paper , the cloth probably has more strength and many like texture. That’s why alligator shoes cost more than
smooth plastic shoes.

[andrew whicker]

I wouldn't use any fabric. Too much work.

With a sander, slightly hollow (about 1/16") the area along the joint. Then use the glass reinforced Bondo to fill it. As long as the joint is sound, it well never telegraph through. I built a 20 cu ft subwoofer and used that method. It has a 1500 WRMS amp driving it and even with that sort of seismic violence going on there's not a hint of the joints.

Nice. How long have you had the woofer?

[andrew whicker]

Cloth might be structurally sound, but I think you'll have a big challenge getting it to the point that the texture doesn't telegraph through the paint.

As to using a vacuum press to adhere anything to a hollow box, you're asking for trouble. The air pressure will collapse the box.

I have an airbag. I will run some samples. Would like to reduce the pressure a bit since I'm only trying to flatten the cloth not glue something together for structure..

[andrew whicker]

Do you have photos you can share? Explicitly where the joints are?


I wouldn't use any fabric. Too much work.

With a sander, slightly hollow (about 1/16") the area along the joint. Then use the glass reinforced Bondo to fill it. As long as the joint is sound, it well never telegraph through. I built a 20 cu ft subwoofer and used that method. It has a 1500 WRMS amp driving it and even with that sort of seismic violence going on there's not a hint of the joints.

[Thomas McCurnin]

Most speakers are wrapped in vinyl for that purpose.

[Warren Lake]

not sure what you want there and dont get where your friend is coming from.

For starters what are the joints. in making pedestals that are no different than a rectangular speaker cabinet all the joints were mitres so the point of the joint was on the radius once all edges were rounded. No one will ever see a glue joint there. What Frank said will also work, ive done that on some other peoples nasty stuff. Feather back into each surface. Same as using bonding adhesive putting body panels on a corvette then feathering back into the body.

While this might be radical and its more a question. They wrap cars all the time can they wrap speakers? Then some are carbon fibre or have parts of them done that way. Lot of hokus pokus with speakers and who can baffle you the most.

Not even sure why you would need bondo or anything on the joints.

[andrew whicker]

I have a description of the process Mel describes in an old boatbuilding book. I will dust it off and see if anything could apply to speakers.

from Boatbuilding Manual Robert M. Steward (fair use)

486425

That's pretty cool. In this case, I was told to use epoxy w/ the cloth. It should give a smooth surface. He has accomplished some very hot rod finishes.

[andrew whicker]

I'm wanting stay away from making 41" long miters (these are big speakers). He runs an internationally recognized speaker company, I just don't get to bend his ear as long as I want. I'm also trying to see if anyone has experience and what their thoughts are. Always open to hearing how someone else has done it, etc.

When he says lines show up using Bondo after a year or so then I listen because he makes these things for a living and does some pretty damn high quality work. I will ask about the Bondo w/ glass. That would seem to fit the bill of between using fiberglass + epoxy and then paint.

The main idea is to use something that covers the glue line and "end grain" of the baltic birch so that it won't show up a year or so down the road. Fiberglass makes sense to me. Muslin was a new material for me, but he said it is easier to work with.

[Bobby Robbinett]

I have built many speakers out of 1” MDF with butt joints. Once the round overs are done and you bondo everything the seams disappear. I have also used vertical grade laminate that will fold over a large round over. I believe that is what Ascend Acoustics used on their speakers for a while. They might still use it, don’t know because I have been out of the hobby for a while.

Another option are lock miters done on a shaper with a power feeder and/or miter folds done on a router, or shaper or table saw.