Subwoofer Problem constant bump with no music ?

My subwoofers in midfle of song started hitting like a hum, but it was a normal bumping sub noise it was just Non stop and Not to the song so i lowered the head untit and it still didnt stop so had to turn car off....... Why ? What could this be ?

Chris2015-12-17T17:38:11Z

sounds like feedback which means something else in your car is interfering with the signal to the sub