Yamaha v1.01 User Manual download pdf (Page 33)

GENERAL GUIDELINES FOR SUBWOOFER DESIGN Page 33/58

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7 GENERAL GUIDELINES FOR SUBWOOFER DESIGN

7.1 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.

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Yamaha v1.01 User Manual Page 33

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