Sub rumble when headunit turns on, or switch songs

[Krown 10+ year member]

Weird. I'm assuming you don't have a second battery?

My friend used to have this problem. I thought it could be the amp ground, so I undid the ground and just ran it up to the negative terminal on the battery to see what would happen. Go figure- sounded fine after that.

 

[Apocalypse boy 10+ year member]

I get a similiar problem. Is the rumbling you hearing in sync with mufflers?