L-Acoustics ARCS User Manual

L-ACOUSTICS ARCS Manual V2.0 2/13/2003 36
c) Separate Flown ARCS Array with Ground Stacked Subwoofers
For a separate flown ARCS array with ground stacked subwoofers, time alignment of subwoofers is
required due to the geometric path difference between the two systems. This is illustrated in Figure
20, where the distance from the measurement microphone position to the subwoofers is d
SUB
while
the distance to the flown ARCS system: d
ARCS
= d
SUB
+ PATH DIFFERENCE. Delaying the subwoofers
by the geometric path difference will time align the subwoofers at the reference position.
Note: Selection of the reference position for time alignment is always a compromise since the geometrical
path difference will vary with position.
STAGE
PATH
DIFFERENCE
MEASUREMEN
T
MICROPHONE
FLOOR
TIME DELAY
(SB218)
(ARCS)
d sub (m)
d ARCS = d+ SUB PATH DIFFERENCE
d
s
u
b
(
m
)
(SB218)
PATH DIFFRENCE (meters)
343 (meters/second)
T =
Figure 21: Illustration of subwoofer time alignment
In most cases, 3W presets are used for flown ARCS and ground stacked subwoofer configurations in
(3-way mode or with separate aux drive for the subwoofers) since the subwoofers are always used
with positive polarity and this helps to simplify installation and system tuning. If more low frequency
energy is desired from the flown ARCS system, 3WX presets can be used with reference to Table 11
for guidelines concerning subwoofer polarity depending on how subwoofers are processed.

L-Acoustics ARCS Specifications

General

Brand	L-Acoustics
Model	ARCS
Category	Speakers
Language	English