Your amp would not be the case to make the crackling noise brotha. CHECK ALL OF THE RATINGS ON THE SUB AND AMP, do that first, make sure they all match. Second, maybe your alternator cannot handle two separate amps. Third, it could be an electrical blow. Just because it doesn't scratch doesn't mean the woofer isn't blown. Take it out of the box and see if the woofer is seperated from the cone AT ALL. Check to see if there's tears in the cone and around the magnet and driver. Last thing, use a multimeter and check to see if it's the sub was blown due to a power surge or something of the sorts. OH and check your polarity homie. + - speaker wires.
Audio Technician. dB contests, Personal Expierience.