Okay I just installed a pair of 12s in a ported inclosure and I get this popping sound coming from the sub. Today I was sitting there looking at them trying to figure out what was happening when the sun got down low enough and shone on the face of the sub, it was then that I saw the face of the sub pop out in the top corner, It just made a little bubble and created the popping noise. Has anyone ever seen this?????????????????