Meyer Sound MJF-212A, Operating Instructions Manual

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10
CHAPTER3
CAUTION:
Please note that the amplifier for
the MJF-212A monitor is different from those
found in other Meyer Sound loudspeakers. Specific
functions for each model, such as crossover
points, frequency and phase correction, and driver
protection are determined by the control cards
installed inside the amplifier. Do not exchange
amplifiers between the MJF-212A and M’elodie or
other Meyer Sound loudspeakers.
mJf-212A INTERCONNECTIONS
The two 2-ohm, 12-inch, low-frequency cone drivers are
each powered with 500 watts from two MJF channels of the
MJF-212A amplifier. The 4-inch diaphragm, 8-ohm, high-
frequency compression driver is powered with 275 watts
from the third MJF channel.
All Meyer Sound loudspeakers are tested and shipped
with the drivers in correct alignment. If a driver needs to be
replaced, make sure the replacement is reinstalled with the
correct polarity.
CAUTION: Failure to connect a replacement
driver using the proper polarity will result
in severe degradation in frequency and phase
response and can harm the drivers and amplifier.
CAblING
The MJF-212A system uses three separate cables and
connectors per cabinet for the AC line current, signal,
and RMS data (if installed). However, the three can be
consolidated to create a “multi-cable” by looming them
together for quick connection to each cabinet. As an
alternative, units can be ordered from the factory with
VEAM all-in-one connectors. (Refer to Appendix A for more
information on VEAM.)
THE lImITING SySTEm
low-frequency limiter
The MJF-212A monitor’s left and right 12-inch cone drivers
are powered by separate amplifier channels, each with
a detector but routed to one limiter. The lower limit LED
on the user panel indicates limiting activity for these two
drivers. When the level for both low channels returns to
normal — below the limiter’s threshold — the limiter will
cease operation.
Figure 3.2: The limit LEDs on the side user panel indicate high- and low-
frequency limiter activity
High-frequency limiter
The 4-inch diaphragm, high-frequency compression driver is
powered by a single channel with its own detector. The upper
limit LED is used to indicate any limiting activity for the high-
frequency driver. When engaged, the limiter not only protects
the driver, but also prevents signal peaks from causing
excessive distortion in the amplifier channel, preserving
headroom and maintaining smooth frequency response at
high levels. When the level returns to normal — below the
limiter’s threshold — the limiter ceases operation.
TIP: The MJF-212A monitor has a side panel
with another set of Limit LEDs so the status
of the monitor can be conveniently viewed from
either side of the stage.
Figure 3.3: Limit LEDs on the side of the cabinet mirror the limiter activity of
the user panel on the opposite side
CAUTION:
The limit LEDs indicate when the
safe power level is exceeded. If any channel
on an MJF-212A monitor begins to limit before
reaching the required sound pressure level (SPL),
consider adding more monitors to satisfy the SPL
requirements. This will avoid exposing the drivers
on that channel to excessive heat and/or excursion,
reducing the life-span of the drivers and electronics.
high-frequency limit LED (yellow)
low-frequency limit LED (yellow)
Limit and
On/Temp LEDs