GENERAL GUIDELINES FOR SUBWOOFER DESIGN
System Manual RS Series Page 39 / 76
6 GENERAL GUIDELINES FOR SUBWOOFER DESIGN
6.1 Low Frequency Issues
Even low frequency coverage is amongst the toughest issues in sound system design. Common issues that are faced in design
are as follow:
Low frequency radiation is hard to control efficiently because of wavelength
becoming large (10m / 30ft at 34 Hz) in relation to sources; and most of
available subwoofers are omnidirectional; this results in important low
frequency feedback on stage, environmental problems in outdoor venues
and increased reverberation time in indoor venues;
Stereophonic implementation of subwoofers introduces very strong
interference patterns; these are related to Left and Right path length
difference to listener location while pressure levels are comparable for Left
and Right arrays; while always maximum at the center – where distance to
Left and Right arrays are equal -, pressure level can severely drop at
locations where path length equals half the wavelength of frequency of
interest. This effect is well-known from audio-engineers, and often referred
to as “Power Alley”;
In closed venues, room eigen modes (nulls and max) are dominant over
source location; because these modes depend on accurate characterization
of boundary surfaces (walls, ceiling, floor), audience coverage is very hard
to predict.
To overcome these difficulties, some common-sense rules can help.
6.2 Gradient Subwoofers benefits
Gradient subwoofers can provide up to 15 dB front to rear average attenuation (Please refer to Ray
Sub technical note for in-detail explanation on gradient subwoofers).
Low frequency level on stage is therefore significantly reduced on stage, and in the neighbouring
environment in open air venues.
Because of their directional pattern, Gradient subwoofer are also less sensitive to room eigen
modes.
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