i think my audio/video system is not getting enough power!! i have 800 watt inverter, and usually when the input is lower than 12v it usually beeps.
currently i have installed 2 12" alphasonic sub, powered by Lanzar 2000w competition amp, connected to a 2 farad capacitor. the speaker is stock and my head unit is stock. i also have a PS2 and a LCD monitor, and a Fm moudulator for sound. the PS2 is connected to the inverter, and every time im watching a movies or playing a game, it beeps. but when i press the gas, it stops the beep. i figure im not getting enough power to the inverter to power the PS2. also my cap should maked up 12.0v, but it always be marking 11.4v or 11.2v or sometimes lower if i turn up my bass.

PLEASE HELP!!!!!!!!!!!

 

What car do you have? If it's a WRX, the alternator has limited capacity at idle and you are probably drawing more current than it can produce, so the voltage is dropping below 12V. The RS alternator has somewhat higher capacity although with all the hardware you have it would probably max out as well.
A capacitor does not increase system voltage, all it does is store some energy to help with instantaneous peaks of current demand, such as bass hits. It can't make up for a weak electrical system.
The only real solution, if you want to be able to run all this stuff, is to find a higher output alternator or have yours rewound. You might also want to replace your battery with an Optima especially if you run your system with the engine off.

 

maybe your alternator is bad, it should be putting 14.4 out to the cap when you are not playing anything loud. also, the ps2 doesnt use a whole lot of juice. but it has to run off constant power, it cant handle the drops that will happen if you play bass loud at the same time. how is your cap wired in to the system? right after the battery then to the amp(s).

 

well here is the diagram of the wiring. it was "professionally done" so i didnt really care about the wiring that much, even though i know how to wire it myself., and it seems ok to me.

 

well the car is MY00 GC8 not wrx. u said a higher output alternator, where i could get one or the cost of a optima battery!!

 

the cost of an optima is from $100-130. but that wont help your problem a whole lot, you will need a new alternator. make sure you look at the power curves though. some claim to make 300000w(or whatever) that is great, but if you look at the chart(kind of like a dyno chart), it comes at 8000rpm(or whatever), which is unusable, make sure you get one with boosted power at idle, where you need it most.

 

The GCs have a 90 amp alternator vs. 75 in the WRX. At idle only a portion of that is available so if you have high current drawing equipment in the car that is where any voltage problems will show up first.
There have been a few threads here and on NASIOC regarding sources for alternator upgrades and unfortunately there don't seem to be that many options. You can search for threads containing "alternator", also check with any electrical shops in your area to see if they can help you out. If you find a local shop that does alternator rewinding/upgrading you may be able to have your existing one redone rather exchange it for a new or rebuilt one.
As for Optimas you can get them at Pep Boys, that's where I got mine. $109 for a Group 35 Red-top, if you want to run your system for long periods with the engine off a Yellow-top may be better for you, they only come in 34 and are a bit more expensive. The Optima won't solve your voltage problems but it will eliminate the battery as a potential weak point in the electrical system as the stock battery doesn't have a very high capacity. You can also deep-cycle the Optimas (particularly the Yellow-top) without damaging them.