Meyer Sound UltraCompact High-Power Curvilinear Array Loudspeaker M'elodie - Manual (Page 25)

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CHAPTER 5
Low-Frequency Design Strategies
While wave guides provide isolated control over various
mid- to high-frequency coverage areas, the low-frequency
section of a M’elodie array still requires mutual coupling
— with equal amplitude and phase — to achieve better
directionality.
Low-frequency directionality is less dependent on the array’s
relative splay angles and more dependent on the number of
elements of the array. At low frequencies, the more elements
in the array (the longer the array), the more directional the
array becomes, providing more SPL and headroom in this
range. The directional control of the array is achieved when
the length of the array is similar or larger than the wavelength
of the frequencies being reproduced by the array.
Optimizing and Equalizing the Array
Once the design (number of elements, vertical splay angles
and horizontal splay angles between arrays) has been
designed using MAPP Online Pro, you can effectively
optimize the array by driving it with multiple equalization
channels, or zones. Typically arrays are divided into two or
three zones, depending the design and size of
the array.
To optimize and EQ the array, different strategies are
used for:
■ High frequencies
- long throws
- short throws
■ Low frequencies
High-Frequency Equalization Strategies
For the far field, air absorption plays a critical role. The
longer the distance, the greater the attenuation at high
frequencies. In this zone, high frequencies generally need
a correction to compensate for energy lost over distance;
the correction needed is usually proportional to the distance
and high-frequency air absorption.
In the near- to mid-field, the air absorption is not nearly
as critical; in this zone, high frequencies need little or no
additional correction.
TIP: If your M’elodie line array uses a third
zone for short throws, high frequencies there
may need to be attenuated to more appropriate
near-field levels.
Low-Frequency Strategies
Although the array can (and usually should) be zoned
for implementing different equalization curves for high
frequencies,
similar or identical equalization should be
maintained in all the low-frequency filters. Different low-
frequency equalization settings in the same array will
degrade the desired coupling effect.
For the same reason, severe gain tapering is not
recommended for line arrays, since adjusting various zones
with an overall amplitude control for each results in the
following:
1. The length of the line array column is effectively
shortened
2. Directionality decreases at low frequencies.
3. Low-frequency headroom decreases.
Figure 5.2 shows a series of MAPP Online Pro predictions
based on an example M’elodie system design. Please
note that small vertical splay angles on the upper part of
the array are used to cover longer distances, while greater
angles in the lower elements to increase vertical coverage
for shorter distances.
Figure 5.2. MAPP Online Pro plots (above right) illustrate the vertical
directivity characteristics of the array (above left), with a section view of
the venue superimposed.
2 kHz
4 kHz
1 kHz
500 Hz
250 Hz
8 kHz
125 Hz