Edge absorbers at the room edges behind the loudspeakers
Edge absorbers are a special form of porous absorbers. Their name refers to their position: at the edges or in the corners of a room. They offer very high absorption coefficients at low frequencies.
Below the limiting frequency of a room the distribution of sound is determined by the room’s eigenmodes. Depending on their eigenfrequency, these standing waves are characterized by a specific spatial distribution of sound pressure and sound velocity. In rectangular rooms one of the maximums of sound pressure and one of the minimums of sound velocity of all room eigenmodes is located in the corners of the room. In the space in front of the corner the sound velocity increases significantly. A porous absorber filling this space can be used to effectively damp the room’s low frequency eigenmodes. This likewise applies to the edges of the room.
The lower limiting frequency of an edge absorber mainly depends on its dimensions. The greater its distance from the wall, the lower the frequencies it can absorb.