Your alt doesn't have to be bad in order to have this problem, it'* when it simply can't supply enough current to feed everything that this happens. At that point it'* just a current capacity issue, in which case the way to fix is to replace the alt with a unit that can supply more current. I'm not saying a cap is completely worthless, I wouldn't agree with that line of thought, but they are not meant to be used in the manner most people use them......to boost an overdrawn electrical system. If you're going to use a cap, your electrical should be up to snuff BEFORE you add it to the mix. That'* the part 99% of people don't realize.

I talked to a Fi Car Audio Rep yesterday and he said 3 cu ft is fine, he also said that the surround "suspension" can "break In" and become softer over time.

i never said the cap was good to solve a problem. all what i was trying to say that it would help a bit if your system is a little short, nothing major, more like a bandage

How does one determine when their system is a little short?

Actually caps DO have a use, just not what the mainstream uses them for.

If you have solid voltage a cap can actually stabilize peaks and valleys in your music. A lot of SQ cars run capacitors as well as battery banks.

That being said if your electrical is subpar, your cap will do nothing more than screw your voltage.

you test the battery its fine
you test your alt its fine
you check the wires they are fine
you dont have money/room/need for a battery

everything have a use out there, and everything can be misused
you are dimming just a bit or dropping a little bit of voltage when you crank it up, thats when you can use a capacitor (and not to forget the type of music you listen to makes a difference too)
you have 15 pieces of 15 inch of 1500RMS subs running 15 capacitors, thats when you can misuse capacitor

Makes sense. I don't feel so bad for having one 1Farad cap now.

That was random

Considering Fi specs a ported box for your sub between 2.8-4 cubes, that'* no revelation. Neither is the fact that the suspension can break in and get softer. No need to talk to a rep to get that info...

I'm no expert when it comes to box building, there are far more factors and specs to consider than the few that i've got a grasp on in order to build a box that maximizes the potential of your setup. If you want to learn about these things, hit me up, but you coming here and repeating what somebody else told you isn't going to trump my nearly 20 years of installing experience so I could make due without the regurgitation of info. I'm not mad, but I have no desire to continue debating the subject with you, that'* all i'm saying.

My comment was in reference to you saying your alternator tested fine, the rest was a general statement and not aimed at you personally.

The only way I know to do this is by using a clamp meter to measure the draw on your electrical system. Or you can do the eyeball test and look for dimming lights, that'* a dead giveaway!

That sounds awfully familiar

If you have dimming, you shouldn't be using a capacitor, simply put.

so what would the problem be?

Lol, if your lights are dimming,

1. your alternator is not powerful enough
2. your wiring isn't big enough
3. your battery is not good enough

Most people who put out insane amounts of power use extra batteries because their alternator can't supply that current constantly when the car'* sitting at idle.

With that Hifonics 1600W @ 1 ohm amp, I could blast it as hard as I want to and the lights won't dim. For kicks I tried unplugging that cap once since its only a 1 farad, and it made no difference. i have 0/1 gauge wiring throughout the whole car for everything large that needs power, and the battery is brand new. The alternator seems to be holding up alright.