Acoustic Diffusers Vs Absorbers
Diffusers and Absorbers are acoustical tools used to “treat” a room, i.e, improve the sound inside the room whether it be large or small. Both tools will improve sound perception in space that, if left untreated, would be a bad influence. Large acoustically designed spaces, such as concert halls, infuse diffusion into its architecture in the way the walls and ceilings are shaped.
Why would we need better sound in rooms? Because most surfaces in a room are hard and flat which strongly reflect sound energy intact. These strong intact reflections cause problems when they come in contact with the original sound, which arrives at our ears directly through air without reflecting. Because the reflections are traveling farther, they are delayed compared to the original sound.
Multiple delays from many reflective surfaces, combined with the original sound wave can add too much echo and reverberation. Equally problematic, delays from sound reflections cause timing/phase errors which disrupt soundstage imaging and cause frequency additions and subtractions called “comb-filtering” (from the shape of the resulting frequency-response peaks and troughs). Accurately hearing original sound, whether from voices, musical instruments, or loudspeakers, becomes difficult.
Absorbers : Absorption is the process of reducing sound energy as opposed to reflecting sound sound energy. The absorbed sound energy is not equal across all frequencies, however, usually causing a shift in tonal perception, with higher frequencies being the most easily absorbed. Most often, an absorptive anel of fibrous material (fibreglass, cotton, mineral wool) is placed in a room on hard, flat sound-reflective surfaces to reduce the energy bounced back into the room.
It is possible however to have too many absorbers in a room, causing a perceptual disconnect between mental expectation of what the sound in the room will be like and an “overdamped” acoustic reality.
Diffusers : Diffusers rely on shifting the phase of the reflected sound to spread the energy. They are most often used on the back wall of listening and control rooms, because the phase-disrupted reflections exhibit lobing (uneven frequency distribution) and create sound-stage imaging problems when used in first-reflection points on the side and front walls.
Diffusion is gaining wider acceptance as an extremely useful and natural-sounding option for helping rooms sound much better.