5.1 (no Atmos)
Use rear ceiling speakers if you want more "height".
Under 15 ft.
7.1 (5.1.2 Atmos)
Only choose this if you're seating is forward of the rear wall with speakers being behind.
20 ft.
Atmos 5.1.4, 7.1.2 (7.1 ok)
You're moving into feeling the full effects of Atmos moving above and around you. Again seating must be forward of rear wall
25 ft.
Atmos 7.1.4 and beyond
Now you have room for all 11 speakers needed to create the full nature of Atmos movie experiences as intended.
Over 30 ft.