The cap only takes that what the battery and the alternator delivers.
For that reason I asked about the voltage at the battery. If you have a high voltage at the battery(12.6V) and a low one at the capacitor(12V) your voltage drop is to high. You are missing 0.6V then.
Thats not much? Ha, put a headlight bulb on 12V and than on 12.6V - you will see the difference.

Its the same with an amp! You will hear the difference!

 

ok bud I understand now I apperciate the help its probily because my batt. is low haven't charged it in a few days while its been broke. I will throw a charger on it when I get home tonight

 

well I finally got the part for my truck and I started her up and let her charge for a while and then I turned my system up and now I'm pushin between 12.5 and 14.96 volts it sounded like they were poundin harder