Meyer Sound Self-Powered Loudspeakers UM-1P - Manual (Page 6)

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Looping, Polarity, and Attenuating Audio
Input Module
This module has a balanced, female XLR audio input
connector, a male XLR loop connector, an input polarity
switch, and a level attenuator knob. With the input
polarity switch in the up (+) position, pin 2 is hot
relative to pin 3, resulting in a positive pressure wave
when a positive signal is applied to pin 2. With the
switch down (–), pin 3 is hot relative to pin 2, resulting
in a negative pressure wave when a positive signal is
applied to pin 2. The level attenuator knob operates
between 0 dB (no level attenuation) in a fully clock-
wise position to –12 dB in a fully counter-clockwise
position.
Remote Monitoring System
The UM-P can be equipped to operate with the Remote
Monitoring System
(RMS) network and software ap-
plication. RMS displays signal and power levels, driver
and cooling fan status, limiter activity, the state of the
polarity switch, attenuator level, and amplifier tem-
perature for all speakers in the network on a Windows-
based PC. RMS is an excellent field-diagnostic tool that
removes the guesswork from troubleshooting during a
performance. All Meyer RMS-compatible speakers use
the same RMS module so they can be easily exchanged
between speakers (depicted on back page). Installing an
RMS module requires only a Phillips screwdriver.
Contact Meyer Sound for more information about RMS.
Amplification, Limiting, and
Cooling System
Amplification and Limiting
Each driver in the UM-P is powered by one channel of a
proprietary Meyer Sound amplifier utilizing comple-
mentary power MOSFET output stages (class AB, bridged,
350 Wrms/ch). Each channel has a limiter that prevents
driver over-excursion and regulates the temperature of
the voice coil. The limiters protect the drivers without
the glaring compression effects imposed by typical
limiters, allowing high SPLs across each driver’s entire
frequency range. Limiter activity for the high and low
channels is indicated by two yellow Limit LEDs on the
rear panel (the high limit is above the low limit LED).
The UM-P performs within its acoustical specifications
and operates at a normal temperature if the limit LEDs
are on for no longer than two seconds, and off for at
least one second. If either LED remains on for longer
than three seconds, that channel incurs these negative
consequences:
• Increasing the input level will not increase the
volume.
• The system distorts due to clipping and nonlinear
driver operation.
While the UM-P limiters fully protect the system under
overload conditions and exhibits smooth sonic charac-
teristics, we recommend that you do not intentionally
drive the UM-P into continuous limiting to attain com-
pression effects.
For applications where large amounts of compression
are required, we recommend using an outboard com-
pressor/limiter for greater control of limit and com-
pressor effects.
Amplifier Natural Convection Cooling System
The UM-P employs a natural convection cooling sys-
tem that depends on air flow from below the cabinet
over the heatsink. Allow for proper ventillation of
fresh air when using the speaker.
If the temperature of the heatsink reaches 85°C (185°F),
the On/Temp. LED on the rear panel turns from green
(On) to red (Temp.) and the limiter threshold is lowered
to a safe level to prevent the amplifiers from overheat-
ing. Under high temperature conditions the limiter
threshold is reduced to 6 dB. When the heatsink tmeperature
decreases to 75°C (167°F), the On/Temp. LED changes
from red to green and the limiter threshold returns to
normal.
! The heatsink gets too hot to touch during normal
operation. Use extreme caution when approaching the
rear of the cabinet.
Fan Assembly Kit
While convection cooling is adequate for most appli-
cations, driving the UM-P into frequent limiting under
severe temperature conditions, or where ventilation is
restricted, an optional fan kit is available to maintain a
safe operating temperature:
The easy-to-install fan, powered by the 24V Fan rear
panel connector, blows air directly onto the heatsink.
The fan speed increases as the heatsink temperature
rises, which maintains a safe operating temperature
with minimal fan noise. Contact Meyer Sound to order
the fan kit.