I have the big 3 done, double runs of 0ga, sundown wire 270 alternator , m4b amplifier 3 3400 xs battries in trunk volts are at 14.3 but when up loud bass note hits and volts drop to 10 showing on bass control knob....p.s. Digital design 9900 series subs are wired to .5 ohm
Do I need more xs battries ???