After recently installing a large sub and amp i'm getting head light dimming, voltage drop off the battery and drop at the amp terminals are considerable.

My first port of call is to address the wiring and earthing, anyone know if there is a specific kit or whether i should just pop into a high street car audio place and ask for bigger wiring (in which case any idea what gauge i should use).

Short of that i'm going to try and find myself a bigger battery (again anyone have any recommendations?)

I really dont want to start looking at power caps just yet as i'm convinced that will only be a quick fix as sorting out the power supply from the front is probably the more scientific approach.

BTW its a 500w at 4Ohms Hifonics son of boltar driving a Kicker Solarbaric S12L7 (2Ohm), the amp has an unofficial 2Ohm rating of 600w and has been very sucessful in the past in previous cars with this load. It just draws a stack load of power.

 

You need a larger capacity battery and 2 gauge wiring.
Thats what I use on my PG 900.1 amp(900w rms@2ohms)

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i looked around, cheapest battery i could find on audio specialists website was a 666Ah Stinger battery but it was about £165!!!

Think I already have 2 gauge wiring, but thats pretty small aint it?

 

2 gauge is some of the thickest around!
0 gauge is the thickest, but becomes unworkable/very expensive.
Just get a more heavy duty battery....

See how you get on then.

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ah i must have 4 gauge then! didnt realise the smaller the number the bigger it was!

you got a better solution to a £165 battery then? or is that just how much they cost, do I have to worry about fitment, i've never had to chose a battery before, they all look the same to me, you know 12v and some posts of varying style.

 

if you are getting dimming lights and voltage drop when the engine is running it means the the alternator can't keep up with the demand, the battery is only there to start the motor and run electrics when the engine is off, the rest of the time it's the alternator that does the work.
As for wiring do check you have a really good earth as this can make one hell of a difference and use the biggest cable you can get, you say you have 4 gauge which should be OK (does it say on the side of wire) but you could try 2 gauge or if this is too big to fit under the carpet try using 1 or 2 runs of 4 gauge, hope this is of some help for you.
Just out of interest i used to use 0 gauge which is nearly 1 inch in diameter (never got any voltage drop but a pig to fit)

 

will have a closer look tomorrow at the wiring, I think the first thing to do is run a proper earth and then replace the main wiring with as thick wire as will fit, i think the guys who installed the system used earthing points at the back of the car, which on an impreza i'm sure are crappy!