I have a single 12" paradigm reference 12 sub. Rotel receiver and amp. BW speakers (5). When I turn up the volume on my stereo to a relatively, but not too high of volume, the sub will cut out for about 10 seconds, then come back on for about 5 seconds, then cut out again. Why is this happening? Is this supposed to happen? What are upgrades to my system that could be done to help this problem out? I am not a stereo guy at all, so I really appreciate all the help. Thanks in advance.