What you want, is to reference all of the speakers to the best seating positions in your viewing area. The 990 will do this in auto setup mode and is usually pretty close. If you want to do it manually then you will need a tape measure and a SPL level meter. Manual is generally more accurate, but auto is much easier. For most rooms you will change the settings slightly in either case because of the sound bouncing around the room. Experiment as much as you want, because you can always go back to the settings you have now. The 990 doesn't really have "room correction" as much as it has a usuable setup mode.