I have 2 amps in a 1996 cavalier with stock alt and cables. The first is an audiobahn a800v powering 2 compvr 12's, the 2nd is a profile 1000ap running my highs. At times the digital volt readout drops to low 11's and even to 10 on some songs. Do i need to upgrade the alt, cables, do i need a capacitor, or both?? I believe when the volts are that low I am not getting the amps rated power to the subs?? I have 4 gauge wire to the sub amp and 8 to the profile with a dual fuse link @ the battery 100A for the 4g and 40A for the 8g.
Have you done the Big3 upgrade? What size fuses are in each amp? Are these the only aftermarket electronic devices in the car?
You've got a 105amp alternator factory.
You'll probably be okay with the factory alt (Big3, of course...) BUT, if you ride around with a lot of electronics on (A/C, wipers, heater, etc...) then it'll be good to upgrade your alternator.
-------------
2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001
The way to approach this problem is to first identify any bottle necks in the electrical system. No body here can see your car and its unique particularities, so we are limited to generalizations.
If I was you I would:
Get my hands on a good multi meter and check if the voltage varies at the battery with the bass while the music is blasting. Then run the same test at the power terminals of the bass amp. If you find that the voltage is dipping more at the amp than at the battery then your problem is in the power wire or grounding of your amp and not an alternator problem.
In the event that you can not get your hands on a high dollar digital multi meter ($100 or better) then you are better off using a cheap radio shack analogue volt meter (the kind with a needle, $20 bucks). The needle does a great job of showing real time voltage issues while the mediocre digital meter will average results and show little change in voltage when the voltage is actually dipping plenty enough to affect your amps performance.
Chances are that if your amps meter shows varying voltage that you do in deed have a problem. But unless you can compare those results with the voltage at the battery directly you have no way of knowing if the problem is do to the alternator or not.
There is plenty more information available here but I suggest running this test first.
Let us know.