Description; Design And Mechanical Features; Electrical And Acoustical Data; Integrated Power Amp - HK Audio SL 218 A Manuel

1 Description

The SL 218 A is a professional subwoofer loaded
with two 18" woofers. It sports two onboard single-
channel, PWM power amps (class-D) with integrated
control circuitry. Its features let you adjust parameters
such as level, upper frequency limit, and polarity
directly at the SL 218 A without resorting to an out-
board controller. If your PA system is driven by an
HK AUDIO ® DFC and you want that DFC to also drive
the SL 218 A, you can use the subwoofer's Bypass
switch to remove its integrated circuitry from the
signal path.
The SL 218 A's hallmark is very low-distortion
very-low-end response at very high sound pressure
levels. It is well-suited to adding sub-bass punch to
full-range systems, and especially to beefing up the
lower low end of systems which already include
subwoofers and mid/high satellite speakers.
1.1 Design and Mechanical
Features
The SL 218 A enclosure contains two separate bass
reflex chambers housing the 18" woofers and a
separate chamber housing the power amps and
electronic circuitry. The enclosure is made of 19-mm,
13-ply birch plywood and coated with water-repellent,
black acrylic enamel. Covering its front baffle is an
impact-resistant steel grille padded with 5-mm thick
acoustic foam.
The SL 218 A weighs just 98 kg despite the integrated
power amps. For easy handling and setup, the side,
bottom and top panels are equipped with eight
recessed handles. Four 100-mm wheels are mounted
on the rear panel for easier transport. A detachable
9-mm thick birch-plywood cover with Velcro fasteners
protects the front grille during transport.
Located on the bottom panel are two wooden rails
on which the SL 218 A sits; located on the top are
two grooves that accept the rails of another SL 218 A.
These hold the top bin in place securely so that you
can set up stacked bass arrays safely.
1.2 Electrical and Acoustical
Data
The SL 218 A sports two 18" high-performance woofers
whose membranes are protected by a moisture-
resistant coating. Each speaker's power-handling
capacity is 1,000 watts RMS at an impedance of
4 ohms.
With the integrated PWM power amps, the SL 218 A's
sensitivity is 105 dB (1 W/1 m) measured on axis under
half-space conditions. Maximum sound pressure
at 1 metre under these conditions in the frequency
range of 32 Hz to 90 Hz is 139 dB with 10% THD.
With the integrated controller, the SL 218 A's frequency
response ranges from 39 Hz (-3 dB) or 32 Hz (-10 dB)
respectively, up to the upper frequency limit. When
an external controller is employed (for example, the
DFC), that external controller will establish the
enclosure's upper frequency limit and Q factor.

2 Integrated Power Amp

The integrated electronics is housed in a separate
chamber within the SL 218 A. It comprises two single-
channel PWM power amps, limiters, protective circuitry,
and mains power supply.
2.1 Power Amps and Protection
Circuits
Each of the two power amps in the SL 218 A delivers
1000 watts RMS output power at 4 ohms impedance.
Both power amps are equipped with circuits protec-
ting them against overcurrent at the speaker output
and against overheating. When a protective circuit
is called into action, the Protect LED on the rear
panel will illuminate.

2.2 Fan

Continuously running fans cool the SL 218 A.
They draw fresh air from the left vent (as viewed
from the back of the SL 218 A) and expel warm air
through the right vent. Located just behind the
vents are 5-mm-thick dust filters of open-cell foam.
Important note!
Check the dust filters regularly and clean or replace
clogged filters to ensure there is sufficient ventilation
to cool the amp. Ensure the vents at the back of the
SL 218 remain uncovered and unobstructed.
2.3 Mains Voltage and Power
Consumption
The SL 218 A requires 230 V mains voltage and 50 Hz
line frequency. The SL 218 A's power consumption
is 2,000 VA.
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