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CHAPTER 3
MICA is performing within its acoustical specifications and
operating at a normal temperature if the limit LEDs are lit for
no longer than two seconds, and then go off for at least one
second. If an LED remains on for longer than three seconds,
that channel enters hard limiting, with the following
negative consequences:
■ Increasing input level will not increase volume.
■ Distortion increases due to clipping and nonlinear driver
operation.
■ The lifespan of the driver is reduced because it is
subjected to excessive heat and/or excursion, and
eventual damage.
NOTE: The limit LEDs indicate when the safe
power level is exceeded. If any channel on an
entire system of MICA loudspeakers begins to limit
before reaching the required sound pressure level
(SPL), consider adding more loudspeakers to satisfy
the SPL requirements without exposing the drivers
on that channel to excessive heat and/or excursion.
FANS AND COOLING SYSTEM
MICA uses a forced-air cooling system with four fans
(two primary and two secondary) to prevent the amplifier
modules from overheating. The fans draw air in through
ducts on the front of the cabinet, over the heatsinks,
and out the rear of the cabinet. Because dust does not
accumulate in the amplifier circuitry, its lifespan is increased
significantly. The front grille surface acts as an air filter for
the cooling system and should always be in place during
operation (Figure 3.5).
Figure 3.5. Airflow through MICA
Because the grille acts as a filter, it should be inspected and
cleaned routinely — once every six months, or once every
three months in a dusty environment — to assure proper
airflow and cooling. The grille can be vacuumed to remove
dust.
TIP: If your MICA loudspeaker is weather-
protected, the grille must be removed in
order to the clean the additional foam underneath
the grille, which covers the air inlets.
Two variable-speed primary fans run continuously and
inaudibly at their slowest speed. The primary fans increase
speed when either of the two heatsinks reaches 42˚ C. The
fans reach full speed at 62˚ C and are still barely audible
even near the cabinet, and without an audio signal. In the
unusual event that the heatsink temperature reaches 74˚ C,
the secondary fans turn on and are clearly audible without
an audio signal. The secondary fans turn on in response to:
■ Primary fan failure (check status immediately)
■ High source levels for a prolonged period
■ Accumulation of dust along the cooling path
The secondary fans turn off when the temperature
decreases to 68˚ C.
NOTE: In the highly unlikely event that the
secondary fans do not keep the temperature
below 85˚ C, the MICA loudspeaker automatically
shuts down until AC power is removed and
reapplied. If the MICA loudspeaker shuts down
again after cooling and reapplying AC power,
contact Meyer Sound for repair information.
Despite MICA’s filtering, extensive use or a dusty operating
environment can allow dust to accumulate along the path
of the airflow, preventing normal cooling. To avoid this, you
should periodically remove the grille frame and amplifier
module and use compressed air to clear dust from the
grille, fans and heatsinks. Make sure that the air ducts are
clear.
TIP: For weather-protected MICA
loudspeakers, the inside foam should also be
cleaned with compressed air.
CAUTION: Be sure to unplug power to the
unit before cleaning the amplifier.
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