If you put your room dimensions into one of the room mode calculators on the ’net, you can see where in the room it’s modes and anti-modes are located (always but not exclusively at the wall/ceiling/floor intersections. Other locations are in the middle of a room’s length, width, and height, as well at 1/3 and 2/3 intervals). If possible, do NOT position your subs (or speakers) at those locations.
ALL woofers work best at the intersection of room boundaries