"The Heat is On" -- ALERT

Silicone is may not the agent for the drying, I feel it is the solvent. So look at the materials used in the mixture. Frankly I would ask questions about this topic to the speaker designers. They would have a better history in dealing with this topic.

Oh man....Armor-All is an AQUAEOUS product containing a monomer that binds a single-molecule layer over vinyl and similar plastics. I don't think there's ANY silicone in it!
The problem with speakers is that some surrounds are made of butyl rubber, for which Armor-All doesn't act as intended.
On vinyl it's great for sealing/protecting the surface.
Silicone mixtures simply COVER surfaces, shining 'em up (tires, etc.). Armor-All shines up vinyl, etc., by returning it to an ultra-smooth surface that reflects light.

Bozo, thanks. Subaru, is there any product that could help in maintaining rubber elasticity -- as in speaker cone surrounds? Thanks

there's a product reportedly suitable for speaker surround treatment mentioned in the last "Stereophile - Fine Tunes" June 2002 issue, before Skull left the mag.
"Meguiar's #40 Vinyl & Rubber Conditioner".
Scull also mentions a couple of other alternatives:
One Grand Exterior Rubber Treatment
Sonax Trim Protectant
J-10 then goes on to review the positive effects of treating his car's speakers with the Meguiar's

Check it out if desired; the article is even available online if you don't have the issue anymore.