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CHAPTER 4
Figure 4.1: 12 and 24 cabinet MILO line arrays
Adjusting Line Array Coverage
Regardless of the needs of your system design, fine-tuning
coverage for a single MILO array will be dependent on three
factors:
Number of Array Elements. Determining the number
of elements to use is critical: Too few elements can
drastically affect the uniformity of coverage of both SPL
and frequency response.
Vertical Splay Angles. Changing the splay angles
between cabinets has a significant impact on vertical
coverage, with the result that narrower vertical splay
angles produce a higher Q vertical beamwidth, while
wider splay lowers the Q at high frequencies.
Horizontal Coverage. Horizontal coverage for a single
array can be considered constant regardless of the
number of array elements or the angles between them.
TIP:
The angle between two or more
line arrays can also be changed to meet
additional design requirements (for example, wall
reflections).
Given these factors, designing and deploying a line array
system will typically have the following objectives:
Even horizontal and vertical coverage
Uniform SPL
Uniform frequency response
Sufficient SPL for the application
16
12 MILO
Cabinets
24 MILO
Cabinets
250 Hz
12 MILO
Cabinets
24 MILO
Cabinets
125 Hz
With two different technologies (low-frequency cone
radiators and high-frequency wave guide) built into each
MILO cabinet, achieving these goals becomes a multi-step
process, with different strategies for the lower and higher
frequencies for long throws and short throws.
NOTE:
MAPP Online, covered in greater
detail later in this chapter, is the tool of
choice to enable you to make accurate and
comprehensive predictions for optimal coverage(s)
during the design phase.
High-Frequency Design Strategies
Planning for high-frequency coverage is a matter of fine-
tuning the splay angles between cabinets while keeping a
eye on the number of far-throwing elements in the array.
The number of elements does not necessarily have a
significant impact on SPL at high frequencies (it will at low
frequencies), but can profoundly affect coverage.
For the far field, a smaller mechanical splay angle achieves
superior throw through better coupling to compensate for
energy lost over distance. In the near- to mid-field, larger
splay angles increase vertical coverage.
Low-Frequency Design Strategies
While wave guides provide isolated control over various
mid- to high-frequency coverage areas, the low-frequency
section of a MILO line array still requires mutual coupling
— with equal amplitude and phase — to achieve better
directionality.
Low-frequency directionality is less dependant 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 more directional the array
becomes, providing more SPL in this range.
Electronically Driving the Array
Once the design (number of elements, vertical splay
angles and horizontal splay angles between arrays) has
been mapped out, you can effectively optimize the array
by driving it with multiple equalization channels, or zones.
Typically arrays are divided in two or three zones depending
the design and size of the array; to optimize EQ, different
strategies are used for the low and high frequencies for long
throws and short throws.
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
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