I usually use my iPod for the truck. Today I was heading to walmart and figured I would don the head phone and drown out the atmosphere. On the way there I was listening to some music via the 30 pin, when I switched over to my head phones it sounded as if there was no bass whatsoever. Several songs all the same, changed the eq settings same results, verified stereo was selected and still horrible sound. Headphones sound fine on my iPhone. Any ideas?