So I was sitting at home fiddling with the EQ on my head with the 410 right in front of me. While cranking it up pretty loud, I noticed that the top two speakers weren't moving at all. The bottom two were jumping around as usual, but the top two were dead. The spec sheets say that the cabinet is divided into two sealed sections. I just find it odd. What would make the top two speakers stop working? Anyone with any ideas?