The best placement for best viewing
Seating layout and screen size are closely connected in any room with AV. There’s some art in seating design, but the rules of thumb are simple.
To size the screen, use the 4/6/8 Rule, where the height of the screen is at least ¼ the distance to the farthest row of seats if you show smaller text, 1/6 for large text, and 1/8 for video only.
Ideally, the closest seat should be no less than 2x the height of the screen.
All seats should be within a 60-degree viewing cone: 30° to either side of a line drawn perpendicular to the center of the screen.
It’s true that most screens and displays will show a good, bright image much farther off-axis, but the image will start to look distorted and text difficult to read. Because of distortion, a 90° cone is your absolute maximum, with 60° or less ideal.
If your room is wider than it is deep, consider installing two or more projectors or displays.
Note that these same rules apply in large rooms or small, no matter what kind of display you choose.