i have 400 watt amp and a 700 watt sub the subs brand is (sony explode) and the amps brand is (rampage) the amp is 2 channel it has been already hooked up from previous owner i just bought it the sub is like cutting in and out and is crackling sometimes the sub has to cords going from it the amp a positive and negative but there is a positive and negative on each channel were do i put the sub cords under the channels there a pictures of a plus and negative with bridge written underneath it i dont know much more about it the other cords r already connected like the earth rem and there are two cords 1 red and 1 black reds plugged in channel 1 and black in channel 2 what do i do????????????????????????