how to turn up the subwoofer

hello guys/girls.... i have a jvc kd-sc500 stereo in my car an i also have 3.5" clarions and 6x9 pioneers in the back....and a alpine type s in the trunk.... the problum is i want to turn the bass up for the sub...(i dont have a subwoofer out put) so i ran it off one of the pre outs an i want to turn the sub up for bass but i dont want to turn up the 3.5s of the 6x9.... im not sure if it is a cross over i should install or what i should put in so i can adjust just the subwoofer....if u have any ideas please let me know

Robert
94 cavalier rs

um simply you dont have an amp... which seperates the bass/mid/highs from you head... everything will go along with each other to some degree but with the amp you can really make the subs take a lot of the bass... try reading up on car audio too b/c they will have really easy solutions too.