[mark_in_manc]

Is the speaker cone beyond saving, or could you glue on a foam surround? I bought some from China on ebay - very cheap, available in lots of diameters, turned up eventually!

Maybe 'naval jelly' (gloopy phosphoric acid rust treatment) might be a good way to clean up the speaker chassis without getting it all over the cone / in the magnet gap, and without abrading it and producing lots of unhelpful ferrous dust.