Ok... I figured I'd stop hijacking that other audio post and start a new one. Although I've been listening to and have upgraded my sound system in the past, i'm still thirsting for knowlege on the subject of car audio. My first question is what do HPF and LPF really mean? High and Low right? Where i'm running in to confusion is my amp has an hpf and lpf setting. Then, my head unit has hpf and lpf settings on it also.