back speakers cut out

back speakers cut out

i have a pair of 6 1/2s in the rear deck connects to 500 watt 2 channel amp and 2 12s connected to a 1200watt amp i have a 4 guage wire kit that splits to 2 8 guage wire for dual amps. both amp share the same remote and ground(wired to one then extra wired from there to other amp). when i keep the volume down both work but as soon as i turn it up the back speakers go out. one of my friends said that its the battery and the other said i needed a bigger altanator(sp?) any suggestions?

you need a capacitor for the bass in order to supply more power to the amp. You might also need to upgrade to a better batter ( yellowtop) and a better Alternator (135 Amps vs. 100/110)