my buddy and i built a custom ported box for my Rockford Fosgate 12. We faced the sub toward the rear end and had the port line up with the fold down compartment of the back seat. It definitely shakes anybody in the car and the windshield acts like a slight deflector thus in my opinion, maximizing bass sound heard within the car. Of course windows up or down, most people can hear me a good bit off. But it's like everybody else was saying, do you want competition sound or just enjoy the bass yourself...