3 speakers out of 4 work?

[6three6mafia6]

im having a little problem and i might have had it for a while , for some reason 1 out of my 4 speakers always sound real quiet, its like half the volume of the rest, i just bought a new amp from soundomain a jbl 300.4px and i noticed that one speaker was real quiet, checked all the speaker wires, crossovers, and then i got to the rca's, so i i switched my fronts to the rear inputs and then one of my speakers from the rear sounded quiet, i switched it back to the front and my front right got quiet, so its always the rca thats the front right, do i need new rca's? i tried my other amp jl 300/4 and same thing front right rca makes whatever speaker its hooked up to quiet, is there a way i can test this without having to take out the HU?

[smoker]

no you are going to have to pull it out and then switch the rcas left to right to make sure it is the cable and not the output on the hu.........