My subs are acting weird..help plzplzplzplz!!!!!!!?

I have 2 12" subs hooked up to a pinoeer head unit, i had the subs and amp unhooked so i could ut different ones in there, and i eneded up not likeing the new ones, so i put the old ones back in, and now when i turn it on, the subs just sit there and bump, but not to a beat, i can have the voulme at 1 or 25, and it stays the sound loudness, but when i turn it up real loud, i can hear the actual beat, but i can also still hear the endless buming sound, i need to know if its my head unit, or my rca wires, or what???