d&b TI 385 d&b Line array design - Manual (Page 48)

11. ArrayProcessing
ArrayProcessing (AP) is a feature to calculate and design
the holistic behavior of a line array. It is an additional
feature to enhance the performance of d&b J-Series,
V-Series and YSeries line array systems when powered by
the D80 or D20.
Physically, ArrayProcessing employs a conventional line
array setup that is properly designed and positioned. The
array must provide the required vertical dispersion and
sufficient acoustic output to cover the audience areas
effectively. Within one array it is possible to combine
loudspeakers with different horizontal dispersions, for
example J12 loudspeakers below J8s.
ArrayProcessing creates individual sets of FIR and IIR filters
for every single cabinet of the array, each of which requires
a dedicated amplifier channel. These filters shape the sound
generated by the array to precisely match a user defined
level distribution and obtain a uniform frequency response
over a given audience geometry.
In addition to individual amplification for each loudspeaker
of an array, ArrayProcessing requires OCA Ethernet remote
control for these amplifiers. The use of ArrayProcessing is
optional, meaning the function can be applied for specific
applications or not, as and when required.
ArrayProcessing adds 5.9 msec of latency, this is in addition
to the 0.3 msec of the d&b amplifiers, arriving at a total of
only 6.2 msec.
11.1 Motivation and benefits
Spectral differences in audience areas
Typically, a line array setup for a given situation is planned
in a way that optimizes the level distribution over distance in
the high-mid frequency range (2 kHz to 4 kHz). This
requires a specific vertical aiming for the individual cabinets
that is defined by the splay angles between them. However,
the array dispersion at lower frequencies (100 Hz to
1000 Hz, depending on the array length) is a direct result
of the total array curvature created by the splay settings
(and not the individual aiming of a cabinet). This often
creates a different level over distance distribution to that in
the high-mid range.
Typical level/distance high-mid vs. low-mid: Changing tonal
balance over distance with progressive curvature.
The effect is well known and has been a cause for criticism
from the very beginning of line array usage in modern
sound reinforcement. The result is an uneven spatial
balance and spectral response from the front of a venue to
the back -
a rich and (too) warm sound close to the array,
which then becomes thin and almost aggressive in remote
areas.
Another well-known example is the difference in spectral
response when covering steep seating areas with a strongly
curved array, as it is often used in outfill and 270°
applications for tiers or balconies. In the highest seats it
sounds very thin, in the seats around the middle there is a
strong and annoying midrange beam, which disappears
again when approaching the stage. In these situations it
can often be perceived that the lower midrange dispersion
does not follow the array shape.
Typical level/distance high-mid vs. low-mid: Changing tonal
balance over distance with constant curvature.
TI 385 (6.0 EN) d&b Line array design, ArrayCalc V8.x Page 48 of 54