How Many UR90 Infrared receivers will I need?One UR90 should provide complete coverage if your room is typical, with a hard surface floor and finished walls and ceiling. However, several things can cause the need for additional UR90s, such as: larger room, odd shaped room, acoustical ceiling, carpeted floors, or book shelves or other things on the walls that can interfere with the infrared signal. How many more you'll need depends on how many of these "impediments" are in your layout room. This Infrared signal should be considered to be line-of-sight, but the IR signal does reflect off of other objects, thus the concern ...