My sub-woofers in my car keep cutting in and out?

I have a system that I have had in two cars now and has worked great no issues until I installed a 1 farad Rockford power capacitor up to it. It worked fine for a few weeks and then one day it just started cutting in and out. I also downgraded to a 40 amp fuse from a 60 if that makes any difference. Any advice on the issue would help.