Home Cinema Acoustics - October 1st, 2008
Home cinema systems are more frequently installed in spaces where the statistical equations are invalid than in spaces where they are valid. Consequently, the meaningful use of acoustic absorption is not limited to its statistical application.
In every dedicated home cinema installation we use absorption to control discrete specular reflections, in spite of the fact that the acoustic panels have no real statistical meaning. Therefore, as we examine the acoustic properties of a home cinema, we need to bear in mind that many times, even large rooms have small-room properties at certain frequencies (especially with regard to specular reflections).
The acoustic size of a home cinema room is a frequency-dependant phenomenon. The attached photo displays the equation that describes the large-room frequency. Below that frequency, we have small rooms in the acoustic sense that we will be dealing with room modes, rather than a statistical reverberant sound field. In physically small rooms like a home cinema, that frequency can fall as high as 500Hz, where it falls below 30Hz in physically large rooms.
A dedicated home cinema is both physically and acoustically small space. Proper engineering will determine how room treatment is used. Application of a good technique at an incorrect frequency is as disastrous as choosing the wrong technique.