Protection Circuitry; Limiting; Overexcursion Protection; Thermal Protection - Mackie DRM18S Owner's Manual

About – Displays the current information about your
subwoofer, including the model, firmware and DSP
versions, temperature, favorite animal and more.
There is really only one reason to go here and that
is if you've been directed so by Technical Support.
CONFIGURATION
MEMORY
LOCK PIN
BACKLIGHT
FRONT LED
RESET
ABOUT
ABOUT
FW : DRM18S v1.0.26
DSP : DRM18S v402
ODO : 56
Temp : 29˚C / 85˚F
Attn : 0.00dB

Protection Circuitry

The DRM18S subwoofer employs a built-in limiter for
less distortion at peak levels. Additional protection
includes automatic thermal shutdown should the amp
overheat. However, with Class-D amp technology, which
is highly-efficient, this should never be a problem.
The protection circuits are designed to
protect the subwoofers under reasonable and
sensible conditions. Should you choose
to ignore the warning signs [e.g. excessive distortion],
you can still damage the speaker in the subwoofer
by overdriving it past the point of amplifier clipping.
Such damage is beyond the scope of the warranty.

Limiting

The driver has its own compression circuit which
helps protect it from damaging transient peaks.
The compressor is designed to be transparent and
is not noticeable under normal operating conditions.

Overexcursion Protection

A subsonic filter circuit just prior to the power
amplifier prevents ultra-low frequencies from being
amplified. Excessive low-frequency energy can damage
the woofer by causing it to "bottom out," also know
as overexcursion, which is equivalent to a mechanical
form of clipping.
1 2 3 4 5 6
1 2 3 4
OFF DIM ON
OFF ON

Thermal Protection

All amplifiers produce heat. DRM loudspeakers are
designed to be efficient both electrically and thermally.
In the unlikely event of the amplifier overheating, a
built-in thermal switch will activate, muting the signal.
When the amplifier has cooled down to a safe
operating temperature, the thermal switch resets
itself, and the DRM18S subwoofer resumes normal
operation.
If the thermal switch activates, try turning down
the level control a notch or two on the mixing console
(or via the Speaker Control knob) to avoid overheating
the amplifier. Be aware that direct sunlight and/or
hot stage lights may be the culprit of an amplifier
overheating.

AC Power

Be sure the DRM18S subwoofer is plugged into
an outlet that is able to supply the correct voltage
specified for your model. It will continue to operate
at lower voltages, but will not reach full power. Be sure
the electrical service can supply enough amperage for
all the components connected to it.
We recommend that a stiff (robust) supply of AC
power be used because the amplifiers place high
current demands on the AC line. The more power that
is available on the line, the louder the speakers will play
and the more peak output power will be available for
a cleaner, punchier bass. A suspected problem of "poor
bass performance" is often caused by a weak AC supply
to the amplifiers.
Never remove the ground pin on the power
cord or any other component of the DRM18S
subwoofer. This is very dangerous.

Care and Maintenance

Your DRM18S subwoofer will provide many years
of reliable service if you follow these guidelines:
• Avoid exposing the subwoofers to moisture.
If they are set up outdoors, be sure they are under
cover if rain is expected.
• Avoid exposure to extreme cold (below freezing
temperatures). If you must operate the subwoofers
in a cold environment, warm up the voice coils slowly
by sending a low-level signal through them for about
15 minutes prior to high-power operation.
• Use a dry cloth to clean the cabinets. Only
do this when the power is turned off. Avoid getting
moisture into any of the openings of the cabinet,
particularly where the drivers are located.
17
Owner's Manual