Thermal Considerations
The HD1221 has two powerful built-in amplifiers
capable of producing a combined 600 watts of rms
power. As an amplifier works, it produces heat. The
higher the signal level, the louder and hotter it gets. It
is important to dissipate the heat as quickly as possible.
This results in increased reliability and longevity for the
amplifier.
The amplifier module is mounted on a large heatsink,
which is cooled by convection where cool air is drawn
through its fins, carrying the heat away. In order for this
convection cooling to work efficiently, it is important
to provide adequate airspace behind the loudspeaker.
Additionally, a thermally-controlled fan resides inside
of the HD1221 which helps to reduce the chance of it
overheating and thermalling. When positioning the
HD1221, we recommend leaving at least six inches of air
space behind it.
In the unlikely event of the amplifier overheating, a
built-in thermal switch will activate, muting the
signal, lighting the thermal LED, and ramping the fan
up to top speed. When the amplifier has cooled down to
a safe operating temperature, the thermal switch resets
itself, and the HD1221 resumes normal operation.
If the thermal switch activates, try turning down the
level control a notch or two on the mixing console (or
the back of the HD1221) 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 HD1221 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 HD1221.
This is very dangerous.
Care and Maintenance
Your Mackie loudspeakers will provide many years of
reliable service if you follow these guidelines:
• Avoid exposing the loudspeakers 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
loudspeakers 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.
13
Owner’s Manual
Owner’
s Manual
