Modal Distribution in Dedicated Home Cinemas - January 1st, 2009
There are three types of modes that occur in dedicated home cinemas; the axial, tangential and oblique modes. The combination of these three types of modes form a dense set of possible standing wave frequencies in the room, and if any of the home cinema’s dimensions are integer multiples of each other, then some of the modal frequencies will be the same and this can cause problems.
It is therefore better to choose non-commensurate ratios for the walls where a home cinema is to be installed. Proper custom home cinema design and engineering will ensure that the modes are spread out as much as possible. Much work has been done on ideal home cinema room ratios. However, the various suggested dimensions are not necessarily the only optimum ones for all room sizes. It is also important to realise that room modes are inherent in any structure which encloses the sound sources. This means that changing the shape of the home cinema, for example by angling the walls, does not remove the resonances, it merely changes their frequencies from values which are easily calculated to ones that are not.
High end home cinema installations would deal with any modal issues by using custom resonant absorbers, offering an effective modal management system in their design.