I have a Paradigm PDR-10 (about 9 years old)-with matching Paradigm speakers (all speakers set to Small via Avia)l and a Yamaha RXV-800 (user manual: http://www2.yamaha.co.jp/manual/pdf/av/english/re/RX-V800kai.pdf) ,Avia calibrator, and a RS sound meter. I think I have calibrated my speakers fairly (I don't need perfection) well in that they all seem in phase and at the same level. However, when monkeying around with the sub, I'm not so sure that I really knew what I was doing. I'm specifically questioning my use of the the two control knobs in the back. I believe that the top one is for output volume and the lower one is for cut off/switchover (?). It is the control and working of the lower knob that I need explained to me. How do I know when I am at a certain Hz cut off point? What is a good, general cut-off to use? Thanks.