Foster FE103a: how to fix stiff treated cloth surrounds

[KT]

Hi,

This is a question for Planet10 or anyone else who has experience with these drivers:

I have a pair of Foster FE103a's that have good cones, but the treated cloth surround on one of them is quite hard and stiff. I can still play music on it, it does flex somewhat, but the sound from this one driver is lower in volume than the other one and not as full sounding.

Incidentally, the other driver's surround is just slightly hard, but much more flexible.

I believe this drying out is probably due to heat and sunlight, but I really don't know the chemistry behind it.

Is there any way of softening up these treated cloth surrounds? Maybe by brushing them with some sort of solvent?

I don't know if these surrounds are supposed to be rubberized, but as they are, they don't feel rubbery. They seem more clothy, but definitely treated.

I'd really like to get these drivers up and running, so thanks very much for your help.

Best,
KT

 

[Scottmoose]

I once revitalised a cracking rubberised foam surround (on a pair of Tannoy drivers) by using some Neutogena hand cream on them. I've no idea if this will work in your case, but it might be worth a try.

Scott

 

[Cal Weldon]

When planet10 did mine, he used butyl-cellosolve. He cleaned the old goo off and left them untreated. Also the plugs, basket and magnet damping and coated the cone.

 

[KT]

Cal,

Good looking driver! I see that you have the holey Coral variation of the FE103a's. I have some, too, and hope to box them up at some point. I hear that they sound great.

The Corals have some rubbery coating on the cloth surrounds. The Foster drivers, however, don't really have a rubbery coating. It's almost like they have nothing at all or some sort of coating that's not thick or textured.

The hardness on my Foster surrounds may be due to drying out, but it also seems like it may be from moisture. I say this because I've observed in towels or dishcloths the tendancy for them to get stiff and crispy after the water has dried out - it think it's the fibers matting together and compressing when wet.

Or it could be some sort of fungus or growth? I notice that there's maybe a hint of some crystalization on one of the surrounds. Not too sure.

In anycase, the cones look in great shape with no sign of moisutre damage or fungus. Just the surrounds are stiff.

Still looking for a solution.

Thanks,
KT

 

[Cal Weldon]

KT,

Can't fool you. Simple laxiness. It was easier to snap a pic of the Coral upstairs instead of going downstairs and taking a shot of the Foster's. If I were home, I'd go down and set that right now that I've been caught.

 

[planet10]

This is still an issue i haven't really sorted out yet. I have lots of drivers with this problem and i'd love to sort it.

Butyl Cellusolve temporarily loosens them up, but they go back where they were after. I haven't found anything that "washes" the loosened hard stuff up.

Ethanol doesn't do anything. Lots of Q-tips & acetone makes some progress, but -- to my surprise -- the Fs went up.

From SY when i was looking for Buytl cellusolve:

Here in the US, butyl cellusolve and the closely related butyl cellusolve acetate are available from nearly every chemical supply house. I would assume the same in Canada, though that may be tougher out in the boonies. A somewhat less toxic alternative you might wish to consider (though BC and BCA aren't terribly toxic) is Dupont's Dibasic Ester (DBE), available from any Dupont distributor. Very similar solvent properties, a little less flammable, and very, very low toxicity.

Anyway, get yourself some Permatex undercoating compound, mix it 50:50 with a low viscosity (say 300-500 centistoke) silicone oil (Dow-Corning 200, for instance), then paint this on the back of the stylus assembly, where the magnetic goop was. Let it dry, then reapply the goop before reinserting the stylus assembly. We used to do this to G1s and FTE/GTEs with great results.

In good condition the Foster surrounds seem to be untreated cloth, but there must be something in there that reacts with sun?, salt?, something to go hard.


dave

 

[KT]

Thanks for your input, everyone.

Since the drivers still play (though with some level mismatch), I think I'll just listen to them and maybe experiment with some of the solvents.

If anyone figures this out, please let us all know!

Thanks,
KT

 

[woody]

I have 2 pair of old fostex 103 drivers. Both suffer from stiff surrounds. One pair
now has a fs of 148 and a qts of .54 that's not so bad but another pair is real stiff
having a fs of 247 and a qts of 1.2 Anyone find a solution for this yet? Maby I
should be shot for thinking about this but would the sound quality suffer if I replaced
the cloth surrounds with foam ones. I also wonder if the spider also gets stiff with
time?