The capacitor probably works fine. The lights still dim, but hey I have a stock alternator and battery so the cap isn't expected to totally solve that. I'm here to complain that every time I turn on my stereo it emits this ridiculous squealing noise. It's basically like the noise one of those old TVs makes but times 1,000,000. I've tried adjusting the voltage which is just about the only thing you can do since its the only control. The noise will go for awhile and then stop and then start, varying in intensity. It also only started when the weather started getting colder, but anyways I hate it :)

most undoubtedly worth buying. i installed this and am running 1200 rms watts. not only is the frequency response better throughout the bass range but the bass is felt more and more in your ear. also matches my amp!

Great product no problems at all smooth transaction and quick shipping

4 farads? Highly unlikely. I'm using an 1800 watt amp and headlights still dim just as bad if not more. The only thing this is good for is an expensive volt meter. I do not recommend and if I could find the receipt i would return it.

Powerful, works and looks great. Easy setup and can handle my amp and subs with ease.

Bought this capacitor thinkig that it would at least somewhat reduce the dimming in my interior and head lights from my 1000 watt rms kicker amp. There was really no difference in the headlight dimming before and after installation, although its supposedly 4 farads. The only really good think about it is that it looks cool.

The first SPL-CP-4X cap I ordered was defective. It would not come up to the battery voltage, and just sat there around 8 volts and beeped and flashed. I sent it back and Sonic troubleshot it and sent me a new one. I have installed the second one and it works great.

Pros:
It's 4 farads for $50 (not too shabby).
My electrical system has no voltage/amp fluctuation even at high volume.
Lights do not dim.
Amp has no strain to sound its best.
Auto shutoff after a few min (no need to advertise to thiefs that you have a system).
Solid construction and good terminals.

Cons:
It's bigger so if you're limited on space, verify the measurements first.
The blue lights are cool, but they are very bright, I put black tape over mine.

I got this in yesterday and it works and looks great. Goes great with my 5500 spl gorilla amp and my 2 12" spl gorilla subs perfect combo.

It work real well and it looks great!

I'm no expert but I think a popping noise coming from the capacitor and a really bad smell coming after the pop is a bad sign, I think this thing just dided on me. :(