When loudspeakers are placed close to walls, the delay between the direct and reflected sound waves affects not only the perceived timbre (due to room gain and comb filtering) but also the degree to which believable phantom stereo images are created. If reflected sound waves arrive too soon after the direct sound, they generate spurious directional cues that spoil the stereo-imaging magician’s trick.
Some people go to great lengths to absorb room reflections with acoustic absorbers and diffusers, but the evidence  suggests this probably isn’t a good idea. These products have inherently uneven frequency response; their presence can drastically alter the timbre of the reflected sound, and it’s harder for the ear/brain to ignore reflections if their spectral content is different from the direct sound. Continue reading