a couple of days ago i got these cheap *** 30 dollar subs from fry's having a sale. theyre 2 8" 350W MA subs in a box w/ tweeters. i hooked them up in the trunk of my car, the way it looks is that there are wires going into the speakers inside the car on that deck thing behind the seat under the window, and then coming with those wires is a little plastic clip on each side with metal contacts. so what i did was get capacitors and hooked them w/ alligator clips to one side of each plastic clip (the positive side so that the bass is taken to the subs) and then clipped the other side of the cap onto speaker wire that went into the red hole. the other wire ran directly from the hole to an alligator clip attaced to the plastic clip. i did this on both sides, and no sound comes out. i took the box inside to test it and it thumps when i hook it up to my home stereo system....so what's wrong? i am using a kenwood 30x4 head unit

 

Did you check if the box already has a crossover network inside?
If so, you don't need to put caps like you're doing. Maybe you afected the circuit when you put that capacitor and the sound is not coming out. Defective or fried capacitor? Maybe.