My toddler enjoys fiddling with my system. He recently pulled out the cable to the subwoofer. Without thinking, I tried to re-connect it to the subwoofer without turning it off. I heard a loud thump before even being able to connect the cable. When I referred to the owners manual, it turned out that I was trying to connect it to the wrong input. I turned off the subwoofer and connected the cable to the correct input. I decided to do a speaker calibration just to check that everything is ok. I got a mesage on the screen that indicates that the subwoofer is out phase -2.0db. Does anyone know what this means and what I can do to fix the problem?