[Arran]

I would scrape the silicone off and use some contact cement instead, silicone makes a lousy cement for speakers, it's too thick, has a habit of peeling off, and looks ugly. I don't know where the idea came from to use silicone to fix speakers, the speaker shops use basically a black tinted version of contact cement, or some other rubber cement, which is usually neoprene based, not silicone based. Silicone is for bathtubs, even fabric glue is preferable.
Regards
Arran