basically, the speaker part in the factory fit sub has broken, is it a special speaker or is it just a normal one? also what size is it?

I've taken it out, but im not sure how to measure it really, are the measured by circumference or diameter?

i can take a picture if needs be,

oh and i notice it has 4 connections rather than two... i know two will be speaker wires, what will the other be for? something to do with it having a built in amp i suspect...

oh and sorry to the mods, i wasnt sure whether this should have gone in the ice section :$