doped cloth surround?

[c3conv]

Does any body know what is the meaning of a doped cloth surround? What is used for doping the cloth and what type of cloth are usually used? thanks in advance.

[LineArray]

From your post i cannot see clearly what your intention is.

If you talk about the surround of conventional speakers a
treatment of the surround or parts of the cone may be used to

- make the surround airtight, if the cloth used is leaky
- introduce damping to the surround (and maybe parts of the cone)

I do not think there is a general recipe used, every manufacturer
will use its own.

Of course most treatments will usually also introduce stiffness and the
resonance frequency of the system can be expected to increase, since
the surround contributes to the stiffness of the suspension of the cone.

There may be several kinds of resins used, i think in earlier times when
the surround was often made of paper and was one piece with the cone,
also bitumen based paints were used. That coating may also prevent
the surround from ageing if the coating/doping has the right consistency
not to brittle during the time the system is used.


I do not know what is commonly used but

- Poly Acryl
- Poly Urethane
- Silicone
- Bitumen
- Poly Vinyl based

are some stuffs which come to my mind ...

What is important is good robustness against the UV radiation
which comes with the sunlight.

If the meshes in the cloth are very fine, even some kind of oil might be
sufficient to make the surround tight. I think it depends on what you want
to achieve.

[LineArray]

- Epoxy based
- Rubber Solution ?

[c3conv]

Originally Posted by LineArray

From your post i cannot see clearly what your intention is.

If you talk about the surround of conventional speakers a
treatment of the surround or parts of the cone may be used to

- make the surround airtight, if the cloth used is leaky
- introduce damping to the surround (and maybe parts of the cone)

I do not think there is a general recipe used, every manufacturer
will use its own.

Of course most treatments will usually also introduce stiffness and the
resonance frequency of the system can be expected to increase, since
the surround contributes to the stiffness of the suspension of the cone.

There may be several kinds of resins used, i think in earlier times when
the surround was often made of paper and was one piece with the cone,
also bitumen based paints were used. That coating may also prevent
the surround from ageing if the coating/doping has the right consistency
not to brittle during the time the system is used.


I do not know what is commonly used but

- Poly Acryl
- Poly Urethane
- Silicone
- Bitumen
- Poly Vinyl based

are some stuffs which come to my mind ...

What is important is good robustness against the UV radiation
which comes with the sunlight.

If the meshes in the cloth are very fine, even some kind of oil might be
sufficient to make the surround tight. I think it depends on what you want
to achieve.

Thanks for your reply. There are two vintage Fostex coax speakers that I can't find the replacement so rather than throw it away I was wondering if I can make my own surround. Since Fostex are quite sensitive I guess putting some fine clothe will be good but what kind of oil would greatly help if you can suggest one.

[c3conv]

Originally Posted by LineArray

- Epoxy based
- Rubber Solution ?

What are some example of epoxy based rubber solution?

[LineArray]

I really cannot tell what kind of stuff certain manufacturers
use, but i remember a german manufacturer, who mentioned to use
phenolic resin as doping for his tweeters - which is another
stuff in the list ... but that was decades ago ...

I experimented with all kinds of stuff, rubber solution is not
very durable when exposed to sunlight. And it is rather
aggressive against some kind of plastic parts when it comes
in contact with. Application is not very easy because it
dries fast.

If your meshes are very fine and you want mainly the airtightening
effect i would give a slowly hardening silicone oil a try.
That stuff is rather durable AFAIK and keeps its flexibility over
long time.

The question is whether you want the doping to be the same
material as the glue between surround/cone and surround/basket.
Won't work with silicone.

If your cone is paper and the cloth is cotton based
white wood glue can be used (maybe dilluted) to glue the cloth
to the cone. For the basket side you will need something different.

Maybe 2-Component Epoxy resin mixed with less hardener to stay
a little soft over time, there are also Cyano Acrylate based Gels
which may be ok for that.

Then maybe apply the oil afterwards to the surround.

But hey, there are very much possibilities ...

I would test the doping on the cloth first to see whether
it leads to the desired result. Then test the glues for
the paper and the basket side separately.

[borispm]

Fostex should be usually in oiled cloth or foam.