Contour Enthusiasts Group Archives Forums Modifications Audio Blown subs??

Hi,
Today I was using my subs and they started to make a "behhh behhh" like noise when I turned them up. Sounds like a plastic hitting noise or a magnet going on a fridge. When it makes this noise I still get bass and everything but it is still very noticable. If they are not as loud they sound fine. I took them out of the box and they look fine. Both of them are like this. I check all my connections already. What could this be??