The guy's room seems pretty good acoustically. The main thing is avoiding resonances / room modes. These will cause peaks and nulls in the frequency response t

The guy's room seems pretty good acoustically. The main thing is avoiding resonances / room modes. These will cause peaks and nulls in the frequency response that cannot be fixed with EQ. The primary way to do this is to avoid right angles; it looks like he has largely done this. In a more typical room where right angles are a fact of life, furnishings and bass traps can help with this. The (lack of) sound absorption is kind of a tricky issue to discuss in a brief manner. On an objective level w.r.t to room interactions, this guy's seating area is closer to the speakers than the side walls. That makes this a nearfield arrangement, meaning that the direct sound from the speakers will be greater in magnitude than reflected sound from the walls. This alone will minimize the effect of reflections. On a subjective level w.r.t. room interactions, somewhat counterintuitively the goal for enjoyable listening is not to create a purely anechoic room totally free from room effects: this sounds unnatural and essentially just recreates a headphones listening experience. One can save a lot of money by strapping on a pair of headphones if that's what's desired. The human brain is, frankly, rather amazing at doing its own "room correction" and hearing through room issues anyway, as long as they're not massive peaks and nulls.