NITID S18WP Apr 2023
7
Amate Audio
4. CARDIOID SUBWOOFERS The S18WP enables the combination of three or
multiple of three subwoofer cabinets in an array to
provide exceptional directivity at low frequencies.
To get the correct set-up parameters, please
at low frequencies has two main effects on the
sound field: firstly, the low frequency level behind
the subwoofer cabinets is greatly reduced;
secondly, in closed venues the diffuse sound field
at low frequencies is reduced so the low frequency
reproduction is much more precise.
Fig. 6. Traditional polar pattern of a subwoofer at 40Hz
The typical operating range of a traditional subwoofer tends to be like a monopole,
i.e. tends to radiate with the same energy in all directions. This behaviour implies
that the control of radiation at low frequencies is very difficult because the
wavelengths are very large compared to the size of the source (8.5 m at 40Hz).
To increase the directivity at low frequencies we must transform the omnidirectional
performance into a cardioid performance. This can only be achieved by various
sources, arranged in a certain position, to which we apply a
specific phase, filtering and delay. That is, we need to
reproduce two signals with the same frequency and similar
amplitude, which will have a difference in phase of
approximately 180º at a certain point of the sound field. If the
phases and delays are well calculated, the result is a system,
in which we cancel the energy of the back and not the one of
the front.
Fig. 7. Cardioid pattern
4.1. The CARDIOID presets
The S18WP can generate an
uncompromised cardioid behaviour when
used in conjunction with an external Amate
Audio processor and their correct set-up
parameters. In its minimum and standard
configuration a cardioid setup consists of a
stack of three subwoofer cabinets or an
horizontal line of three subwoofer cabinets.
Only one subwoofer is needed to
compensate for the energy of the other two
radiating to the front. Then, the cabinet
facing to the back (to the stage) should be
located in the centre of the column or line.
Fig. 8. Cardioid configuration for S18WP
(stack)
