GENERAL GUIDELINES FOR SUBWOOFER DESIGN Page 35/58
Main drawback of monophonic designs as the ones described above is inconsistent phase relationship
between subwoofer arrays and main systems over the audience area (lack of impact in the 80Hz-125Hz
bandwidth).
7.4 Stereo Design
If stereophonic implementation has to be maintained, then Left and Right array coverage patterns have
to be as independent as possible – ie coverage overlap from Left to Right has to be minimized.
When using few cabinets, minimizing overlap can
only be achieved with directional devices by
rotating the subwoofers 30° to 45° outwards
(rotating an omnidirectional subwoofer makes no
difference in the coverage pattern).
When using a larger amount of cabinets, Left and Right subwoofers arrays must be designed so that
level drops as much as possible inwards, and is maintained as going outwards. Therefore, main axis
efficiency must be orientated outwards (through use of delays or curving the array outward as in below
figure). Such arrays must be experimented playing one side only to check if above condition is fulfilled,
and then summed left and right for interference evaluation (see below drawings). Although pressure
level will still drop in the centre vicinity, overall level in the audience area is comparable to what occurs
at the centre.
LEFT IMPLEMENTATION MINIMIZING RIGHT COVERAGE LEFT AND RIGHT SUM
Advantage of stereo design as oppose to mono design is much improved phase relationship between
subwoofer arrays and main systems since distance between them is greatly reduced.
However, it is essential to keep in mind that stereo subwoofer array design always leads to strong
interferences in the centre alley vicinity (a couple of steps left and right of mixing position).
A successful design requires minimizing the audience area over which these interferences occur, and
therefore lots of on-site experimentation.
Curved Sub Array
Steered Sub Array
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