I had purchased a pair of PSB Century 1000i speakers but I had to take the sub as well because it was a package deal. The sub is an OLD PSB Subsonic II with a 12" driver in a dual ported box. I turned it on and it hummed like Gomer Pile on meth. I took it to my technician and he replaced a few bad capacitors. Its now quiet and works really well, good enough to give it to my son-inlaw.