Mackie SWA1801 User Manual - page 11
11
Architect’s and Engineer’s Specifications
The active subwoofer loudspeaker system
shall incorporate one 18-inch low-frequency
(LF) transducer mounted within a vented
enclosure and tuned for optimum low-
frequency response. System frequency
response shall vary no more than
±
3 dB
from 45 Hz to 120 Hz measured on axis.
The loudspeaker shall incorporate a low-
frequency amplifier system capable of
delivering 900 watts RMS over a frequency
range of 30 Hz to 150 Hz. The system shall
provide 129 dB of continuous output and
135 dB of peak output. The amplifier sys-
tem shall be mounted on an aluminum heat
sink, which shall be mounted on the rear of
the enclosure, and shall be convection cooled.
The rear mounted amplifier assembly
shall comprise separate signal and AC
power panels separated by a large alumi-
num heat sink. The signal input panel shall
contain two input and two loop-through
XLR connectors, two high-pass output XLR
connectors, a volume level control, a phase
switch, and four status LEDs for Power
ON, Signal Present, Limit, and Thermal
functions. The system shall accept a stan-
dard line-level signal via the XLR input
connectors. The power switch and IEC AC
connector shall be located on the power panel.
Thermal protection shall be provided by
a thermal sensor mounted on the heat sink,
which monitors the heat sink temperature
and triggers the thermal protection circuit
should the temperature exceed 140
°
F (60
°
C).
The Thermal LED shall light and the input
signal shall be muted until the heat sink
cools to a safe operating level, at which
point the thermal protection circuit auto-
resets and normal operation resumes.
Overload protection shall be provided by
a limiter circuit, which monitors the low-
frequency amplifier output and reduces the
input level to the amplifier should the am-
plifier output begin to clip.
The enclosure shall have a rectangular
shape and shall incorporate two side
handles, one on each side, and a top-
mounted pole receptacle. The enclosure
shall be constructed of multi-ply wood.
The active subwoofer loudspeaker sys-
tem shall be the Mackie Designs SWA1801.
SWA1801 On Axis Frequency Response (with second and third harmonic components)
Fundamental
Second
Third
20
20k
50
100
200
500
1k
2k
5k
10k
Frequency (Hz)
40
60
80
100
90
70
50
110
SPL, 100 dB @ 100 Hz