I recently bought a custom made, closed backed, 2 12" speaker cabinet that I installed two 12" Green Beret speakers in. I have a PRS custom 50 head that I hooked the cabinet too. I set the head on the cabinet and turned on the amp. As soon as I turned it on the speakers starting feeding back. It didn't matter if I had a guitar plugged in to it or not. It also didn't matter what the volume on the amp was set to. Once I moved the head away from the speaker cabinet, it went away. I was wondering what I need to do to stop this. DaveB