8
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M3D
™
Line Array Meyer Sound Laboratories Inc
M3D Peak Limiter
When engaged, the Peak Limiter prevents signal peaks
from causing distortion in the high channel, preserving
headroom and maintaining smooth frequency response
at high levels. Peak limiting is indicated by the Hi Peak
LED on the user panel; the same on/off cycle discussed
for the TPL limiters applies to the Peak Limiter.
M3D-Sub TPL Limiters
The 18-inch front low-frequency drivers are driven by
separate amplifier channels but are fed by one limiter;
the LO TPL F LED on the user panel indicates TPL activity
for these drivers. The rear 15-inch drivers are connected
in parallel and driven by a single amplifier channel that is
fed by one limiter; the Rear TPL LED on the user panel
indicates TPL activity for the rear drivers. The limiters
cease operation when the power level returns to normal,
and do not affect the signal when the LED is inactive.
M3D-Sub Excursion Clamp
The drivers in the M3D-Sub are protected by an
excursion clamping circuit that provides instantaneous
braking for the drivers without the pumping effects
commonly produced by compressor/limiters.
The circuit uses sophisticated filters to minimize the
distortion normally caused by clamping and clipping. As
the M3D-Sub’s input signal is increased past the clamping
point at each frequency, the output signal remains at a
fixed level for that frequency, protecting the drivers and
minimizing negative sonic effects. The LED, shown in
Figure 15, illuminates when the maximum allowed peak
voltage at each frequency is reached. This circuit works
for all frequencies, not just very low frequencies where
the drivers are more vulnerable overexcursion.
The M3D-Sub operates safely if the Exc. Clamp LED is on
for no longer than two seconds, and off for one second.
FANS AND COOLING SYSTEM
The M3D uses a forced-air cooling system with four fans
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
grill surface acts as an air filter for the cooling system
and should always be in place during operation.
Despite the filtering, extensive use or a dusty operating
environment can allow dust to accumulate along the path
of the airflow, preventing normal cooling. We
recommend periodically removing the grill and amplifier
module and using a vacuum cleaner to clear dust from
the grill, fans, and heatsinks.
Make sure that the air ducts are clear.
NOTE: The TPL LEDs indicate when the safe
power level is exceeded. If an entire system of
M3Ds begins to limit before reaching the
required sound pressure level (SPL), you
should consider adding more loudspeakers.
Figure 15. M3D-Sub limit LEDs
WARNINGS:
THIS PRODUCT MUST BE GROUNDED
This surface may reach high tempuratures white in use.
To ensure proper operation, allow at least 6 inches
clearance from this surface and adequate ventilation.
To reduce the risk of electric shock do not remove cover.
No operator or serviceable parts inside.
Refer servicing to qualified personnel.
To reduce the risk of fire or electric shock
do not expose this appliance to rain or moisture.
ATENCI N: ACCESO INTERNO SOLO
AUTHORIZADO A PERSONAL T CNICO CALIFICO
ACHTUNG: GEHˆUSE NICHT OFFENE WARTUNG
UND REPARATUR NUR DURCH ELEKTROFˆCHKRAFTE
ATTENTION: ENTRETIENET REPARATIONS
INTERNES NE SONT AUTORISEES QU’AU
PERSONNEL TECHNIQUE QUALIFI
U.K. WARNING: THIS APPARATUS MUST BE EARTHED.
NO OPERATOR SERVICEABLE PARTS INSIDE.
REFER SERVICING TO QUALIFIED PERSONNEL.
Figure 16. Airflow of M3D
!CAUTION: Be sure to unplug power to the
unit before cleaning the air filter.
NOTE: Always use the rain hood in the fully
open position to maintain proper cooling of
the amplifier.