Making diy foam/rubber surrounds

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Yes, I know the commercial ones are fairly inexpensive, but what I really want is rubber, not foam. It seems like it would be easy to make a circular half-round groove in a piece of wood or plastic using a router, then apply some mold release and paint it with liquid rubber or 2-part RTV. Strip it out and there's your new surround. Has anybody tried something like this?
 
I have made similar silicone structures in the past. You will need to make a mold and cast it instead, as you can't controll the thickness of the material otherwise.

Counting that little detail out, it's fairly easy and simple to make such. I would go for a sillicone based compound, as you can relatively easy control the hardness of such a compound, and it can be changed by simply changing the propotions of the mix.

Magura :)
 
Hmm... that little detail. I have a mill/drill and rotary table, so making the half round depression is no problem. I'll have to think about how to make the mating half of the mold. There are radius cutters that would do it, first on the ID, then the OD. Same thing can be done with the router, but I don't know how successful I'll be making parts that mate accurately enough to keep the thickness constant. I assume they make the commercial ones the same way, but with better tooling?
 
Conrad Hoffman said:
Hmm... that little detail. I have a mill/drill and rotary table, so making the half round depression is no problem. I'll have to think about how to make the mating half of the mold. There are radius cutters that would do it, first on the ID, then the OD. Same thing can be done with the router, but I don't know how successful I'll be making parts that mate accurately enough to keep the thickness constant. I assume they make the commercial ones the same way, but with better tooling?

Mill the Negative half flat in the mill first, then cut the groove without disturbing it. Mill the positive haf flat then put a series of holes around the circle in the flat piece and put short screws in. Coat the negative half with release agent. Clean the positive half with the screws. Assemble and fill with epoxy. This sticks over the screws and makes the positive half of your mould.

Use plates of sheetmetal to space the two halves of the mould apart to form your flanges and to allow you to change the thickness by changing the bits of sheetmetal.

While you're at it you may as well add a feathered or patterned inside edge if you're into the Enabl/Mamboni thing.
 
Conrad Hoffman said:
Hmm... that little detail. I have a mill/drill and rotary table, so making the half round depression is no problem. I'll have to think about how to make the mating half of the mold. There are radius cutters that would do it, first on the ID, then the OD. Same thing can be done with the router, but I don't know how successful I'll be making parts that mate accurately enough to keep the thickness constant. I assume they make the commercial ones the same way, but with better tooling?


The way to go about it is to use a radius mill and your rotary table. That's the way we did it before CNC equipment became an option.

Make sure you incorporate a couple of cylindrical guides to align the two halves.


Magura :)
 
I'm probably too fussy, as I'd want different radii on the two parts, so the thickness of the surround would remain constant. Too big a pita, so I think I'll just go with the purchased item! Thanks for the comments- maybe someone more ambitious will have at it!

edit- BTW, I've had several drivers over the years that needed new surrounds. I just picked up a pair of junk JBL 2600s that need 'em, and IMO they aren't worth putting much (anything?) into, but will be nice to practice repairs on.
 
It seems like it would be easy to make a circular half-round groove in a piece of wood or plastic using a router, then apply some mold release and paint it with liquid rubber or 2-part RTV. Strip it out and there's your new surround. Has anybody tried something like this?

Yeah, somebody has tried it, done it actually. There was a really nice detailed article in AudioXpress a year or two ago. I don't know the guys name, or exactly how long ago the article was published, but I bet a search on the AudioXpress site would turn up the information quite easily.

JJ
 
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