Originally Posted by Enoch
Using this formula, I would need an 180 in. diagonal screen! Not going to happen for me.
I understand. How close can you get to that size? These recommended sizes are indicated by the behaviour of audio in the room, which establishes a sweet spot. It also is standardised by THX Cinema standards, which give us these screen sizes, based of viewing angles and audio angles to the L and R side of the screen and the speakers. Of course you can have any size screen you like, these recommendation give you a screen with the same viewing angles as from the mixing position in the dubbing stage, where the film is made.