SUMMARY
Many claims have been made in recent years as to the
“unique” performance characteristics of modern line array
systems. The simple reality is that, for standard, curved or “j”
arrays the performance is very well behaved because the device
spacing and cabinet spacing are always small or comparable to
the wavelengths being radiated. It is simple and straight forward.
The attenuation of SPL is 6dB per every doubling of distance
from the system (in the far field). That is exactly the behavior
of a classical spherical radiating source. It is true that linear
sources can exhibit a reduction of only 3dB for each doubling
of distance but this occurs only in a limited section of the
near to far field transition and is frequency dependent. What is
more noteworthy is that this 3dB per doubling of distance
behavior is only possible when the array geometry is perfectly
flat. Initial line array users attempted to use flat arrays and
always noted unacceptable included vertical angle performance
(whether indoors or outdoors) and also noted extreme difficulty
in matching the SPL coverage versus distance in the venue
with the flat array’s major lobe (for curved arrays the near field
behavior is likely between 3dB and 6dB per doubling of distance
and is very difficult to quantify).
It should also be noted that line arrays, although offering
substantial benefits, are not suited for all applications. A line
array needs proper aiming or sub standard performance will
result. Line arrays are not suited for low ceiling venues or
venues that don’t generally match the included horizontal
angle of the system. Conventional “cell arrays” of high Q
elements, although suffering from all of the polar lobing errors
noted in this paper, are often a better overall solution for low
ceiling environments or long and narrow rooms.
Any attempts to use line arrays without good “application
specific” aiming software can result in more frustration than
success. Many manufacturers offer good line array CAD routines
that will enable an educated user to achieve excellent results.
An additional advantage of aiming software is that it can
be an excellent educational tool. A novice user can quickly
work through a large variety of line array geometry and venue
styles and easily see all of the concepts discussed in the paper
come into practice.
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