low voltage

Equipment Optima sc34du..cca~ 750 hot is around 950 170amp alternator Soundstream rubicon mono 1600  Rms Soundsteeam Lil wonder 4.580 Power acoustic 40 farad capacitor  Wiring 4 gauge from - batt to engine 0 from batt to chassis 0 from battery to capacitor, 0 ground for capacitor as well.  0 to distribution block All amps ground and power is 4 gauge  Reading Car off- 12.91 v Car On- 14.47v Car on with bright lights fogs and ac  12.52v Music on not loud soft bass 13.1 with engine fan 12.5 Medium base and mids 12.0 lights dim on dash...which gets power when volume increase.. The sub- pioneer 3000 watts reads 1 ohms so the coils are still good.. The wire from the positive to the fuse box is oem..not sure if I have to change that.. Midrange is 2 6" and 2 6*9 Help me out have no idea why voltage drops so muchIts easy like pie

Car is a 90 Integra with b20Its easy like pie

Upgrade the Big 3, and try putting the cap at the fusebox instead of at the amp. Caps are useless. But since you already have it, it may help the dimming if it is at the fusebox instead.

I did the big 3...0 guage from the batt to the alternator...0 from battery to chasssis and also 4 from the engine to the chassis Concerning the cap..the dimming isn't a problem but the low voltage is...it's too low for such a draw ESP when the system is lowIts easy like pie

AnyoneIts easy like pie

Measure voltage at the alternator. 1600W RMS is up to ~160A hence it is likely your alternator isn't big enough - even if at sufficient RPM and with copious wiring.