I wouldn't recommend getting a capacitor... when it comes down to it, it's basically a temporary, weak battery..
it would be more efficient to put a second battery (kinetiks are good) in your trunk.. but first you should get a HO alternator to power it
just my opinion
I agree completely,... there is a lot of smoke and mirrors and voodoo science when it comes to car stereo. I took a lot of electronics in school and alway judge stereo analytically.
If it were me, I'd put a 12V sealed lead acid battery from something like a 12V weed eater or something and mount it as close to the Amp as possible with thick (but not too crazy) and short wires connected in parallel to the Pos. and ground of the amp. People say that a capacitor has "faster discharge" speed but I was playing with rechargeable lead acid battery (about 3"x5"x5") and accidentally touched the wire across the terminals. It was wire a little thicker than bell telephone wire and it instantly turned red hot and melted.
That's a pretty fast and powerful discharge in my books. I'm pretty sure the same wire would have just discharged one of those huge 1 farad caps with a spark and no melting. Those caps can be hundreds of dollars and a new smaller lead acid battery can be $10 or $20 at a surplus store. (a normal motorcycle, atv or lawn mower battery would work too but you might have to worry about leaking acid in your trunk .)
Speaker and amplifier specs can be misleading as well. I remember looking at an in-dash head unit years ago with '300 watts' printed on the side. If the amp in that head unit really put out 300 watts RMS continuous, it would melt the dash in your car and probably start on fire. Upon closer inspection it only put out 20 watts continuous but will put out 300 watts for a microsecond (max peak power) as will any amp. That 20 watts was with 10% distorsion too.
Speakers too are misleading,.. it's not the power handling capacity that matters it's the SPL (sound pressure level measured db watt meters) that really has an impact. That spec tells you the sound pressure of a driver (speaker) measured one meter away from the driver with a 1 watt input. The really high power handling drivers (especially woofers) tend to NEED a lot of power to be loud. They tend to have a SPL of less than 90 db sometimes in the low 80's. If a woofer has an SPL of 80 db's it needs 100 times more power to be as loud as a woofer rated at 100 db watt meters.
If you can find a woofer that puts out a SPL in the high 90's and can still handle high power, then you've got some real sound power. (every 3 db increase in SPL of a driver reduces the power demand by half to be as loud)
I have issues with that super thick and expensive monster cable and such. I bought a pair of old school home speakers from a guy (Cerwin Vega 12TR's,... 100 db watt meter with a max of 120 db at 100 watts) who had two 6 foot speaker cables attached to them worth $800,... made out of gold. I took the speakers apart to find the equivalent of bell telephone wire inside the speaker itself.
I was talking to a guy at a stereo shop about monster cable and he took me into a sound room to tell me that his brother works at a government lab that tests speakers in an anechoic chamber he said all the use is lamp cord to do all their testing. Monster Cable has less resistance so it's more efficient but hardly worth the money. Spend your money on quality drivers instead,... way more bang for your buck.
The power feed wires to a car amp are a different story,... they deliver huge amps and need to be thick,... I just used welding wire,.. it's a lot cheaper and works fine,... it's nice and flexible too.
I kinda drifted off on a tangent there but I think it still relates to the OP's question.
