@underdog69, This sounds like you have a speaker hum.
There are a number of reasons why speakers start to hum, one of them is a ground loop has been introduced, being the one most often seen causes. Another reason is as @salmonjapan said, dry solder joints or high ESR / shorted electrolytic capacitor(s). (You need an ESR meter to test the capacitors.)
I’d start by opening the sub up and inspecting the board inside and then evaluate. If you take some good quality and up close pictures, then update our question. [guide|21499|Adding images to existing questions].