Ceiling reflections cannot substitute for side-wall reflections.

Evidence

However, it has been found that the pseudo-lateral diffuse reflections from the ceiling are not quite comparable in effect to reflections from the side walls, and so the provision of a good listening environment within the realities of economics is still a challenge. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1934

Categorization

• QUESTION: Why are side-wall reflections psychoacoustically better than ceiling ones? Worth chasing the underlying mechanism (likely related to inter-aural timing differences and spatial impression).