Jonny v

I just purchased an Fi BL 10in dual 2ohm sub from Fi. My amp is an Hifonics Brutus 1208 with 4 guage wiring. i hooked the sub up yesterday at a 1ohm load, turned the amp around a quarter of the way up and listened for a little while. It started having a cracking sound like the voice coil was cracking but it dosen't do it at low volumes just around half way up which isn't loud at all also my deck is stock at the moment. Please give me advice on what the problem might be dealer fault or mine.