okie here is how i use the gain control.and here is how the story goes.pada zaman dahulu, i got 2 component sets. 1 set front 1 set rear. 1 day when i was driving my car i notice that my stereo doesn't sound rite. the vocal coming out from the front comps are all over the front winscreen. it doesn't stay focus. okie what struck my mind at that time was the gain control. there was a slight diff in loudness from L and R. what i did was, i took a spl meter. feed my comps with pink noise. measure the DB and voila. diff in few DB. so i went back to the rear of my boot(where my amps is) and tweak around the gain control. guess what, the vocal stay put on a spot.