check your wiring (like srv1 said with bridging)...you may not be giving it enough power..you need power for clarity (and a decent sub)...10s are usually clean down to the 30hz region...also check your headunit settings...maybe you have the low tones and bass up all the way or something silly like that...but i dont see why you should need anything thicker than 10gauge wire for power to a 10" RF sub...but if youre using plain 24gauge speaker wire, maybe you should spend a couple of bucks on a setup kit...buy em at circuit city...etc...real nice and clean...come with a fuse box too.
-jonathon