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APPLICA
TIONS
39
38
CARDIOID SETUP
Cardioid configurations follow the same acoustical principles as end-fire setups but deal with shorter
distances between the subwoofers. This can be an advantage in many applications where space is scarce
but, it implies also some compromises regarding front SPL.
A classic cardioid setup is achieved by combining three subwoofers in a ratio of
2:1.
This means two
subwoofers facing front or towards the audience, and one subwoofer facing rear or towards the stage.
Figure 38 shows possible arrangements for these arrays.
The amount of rejection in the rear side of the subwoofer setup varies with frequency, and depends
strongly on the chosen arrangement and the acoustic environment. In half-space conditions such as
outdoors, a rear-rejection of 15 to 20 dB can be achieved. Also, the stacked arrangement has proven
to be the most effective.
Compared to a single subwoofer usage, the response of a cardioid arrangement exhibits an
increase in the level of the highest frequencies of the subwoofer's range. If desired, and in order
to retrieve a flat spectrum, a parametric EQ around 85 Hz with a Q3 and gain of at least -3 dB
should be used equally on all the subwoofers of the array.
As explained before, the Directivity function in
B 15A
self-powered subwoofers highly simplifies this
process. To do it, just:
1. Select the "Normal" mode in the Directivity menu of the subwoofers facing front.
2. Select the "Cardioid" mode in the Directivity menu of the subwoofer facing rear.
All the additional processing like level, delay and EQ, should be done identically to all
subwoofers within the cardioid setup, in order to maintain proper phase relations for
directivity control.
Conversely, in cardioid setups comprising passive models of the B-Line, the required delay must be
applied before in the signal path. Also, their internal circuitry simplifies the connections, as shown in
figures 39 and 40: notice that only one speakON® NL4 cable is needed between the amplifier and the
subwoofers, where the signal is shared and passed through pins 1+/1- of the speakON
®
link cables.
In addition, notice that all the connections can be made only from the rear of the arrangement,
improving the appearance of these deployments.
Figure 38.
Horizontal and vertically stacked configurations for cardioid setups.
FRONT
(Audience)
FRONT
(Audience)
REAR
(stage)
REAR
(stage)
