the bigger, the louder. and it will rattle your car more on the deep hits. but the smaller the better quality. if you listen to rap and rap only get an 18 or 15. i listen to rap and rock. and to me a 12 is perfect cuz you still get that punchey bass (alot better with a 10 though) and it hits and rattles my car on the really deep notes still. its like having a 15 and a 10.