Nexo RS - Manual (Page 32)

Page 32/54 G ENERAL GUIDELINES FOR SUBWOOFER DESIGN
f1=C/2L
L(m)
f1=C/2L
L(m)
6 G
ENERAL 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.