Operating Instructions
Meyer Sound Laboratories, Inc.
2832 San Pablo Avenue
Berkeley, CA 94702
M-5
Control
Electronics
Unit
Operation Once all the connections have been made and verified,
the system is ready to operate.
Note: Check the voltage selector switch located on the
rear panel of the M-5 and verify that it is set to the
range that corresponds to the mains AC voltage.
• The M-5 Attn control should be set at minimum.
• Switch on AC to the M-5 first, then to the power
amplifiers.
• Verify that the power amplifier voltage gains are fixed at
+16 dB (6.3 volts out for 1 volt in, measured from bal-
anced input to speaker output terminals).
• Advance the M-5 Attn control to set the system sensitiv-
ity. If the system is not operating properly, recheck all
connections.
Note: The Attn control markings are merely a visual aid and
should not be used to balance two systems. The output of
the M-5 is calibrated only when the level control is fully
clockwise.
The setup controls on the M-5 front panel are designed
to be used to tailor the system response for particular
applications.
Safe/Autosafe Switch. The M-5 incorporates three
limiters in the MultiSense™ driver protection circuitry
(see detailed description below). When the switch is in
the Safe position, the RMS limiters come on at 6dB
lower power levels, affording added protection when
heavy continuous power demands are placed on the
system. For operator convenience, a green LED
indicator is provided on the M-5 front panel which lights
when the M-5 is in the Safe mode. When the switch is in the
Autosafe position, the M-5 monitors system power over
time and automatically switches into Safe mode if the power
demands become too high. In the case that Autosafe
switches the M-5 into Safe mode, the green LED will light to
indicate the change.
Note: It is recommended that the switch be in the Safe
position until the operator is familiar with the system’s
capablities.
Front PanelControls
• Supply an input to the M-5, preferably a sine wave oscil-
lator. If you do not have an oscillator, use a microphone
and a mixer to produce a line level signal.
• Set the input frequency according to this table:
Oscillator Microphone
Lo limiter 200 Hz low growl
Hi limiter 5,000 Hz loud whistle
• Bring up the input until you see the corresponding limit
indicator come on. Since in each case the indicator will
light only if the limiter actually operates, it provides a
positive indication that the limiter is functioning.
To verify limiter operation in the field:
• Disconnect loudspeakers, leaving the amplifier and
the M-5 in their standard connection configuration.
• If your amplifier requires a load, use resistive loads
sufficient to dissipate the full power of the amplifier.
• Turn on both the M-5 and the amplifier.
• Set the Safe switch in.
Limiter Operation
Through the Sense connections between the M-5 and
the power amplifiers, the MultiSense circuitry of the M-
5 continuously monitors the voltages across the high
and low frequency drivers. If the amplifier output
exceeds the safe operating limits of the drivers, inde-
pendent limiters are automatically activated, holding
down the level of the M-5 output.
Note: The M-5 employs an excursion limiting system
which assumes

a fixed amplifier voltage gain of +16

dB (6.3 volts out for 1 volt in)

. Please refer to the
MSL-5 Operating Instructions or the Meyer Sound
MSL-10A Power Amplifier Criteria note for a detailed
description of MSL-5 / M-5 amplifier requirements.
The operation of the MultiSense circuitry is indicated by
a set of five LEDs located on the front panel.
•Sense indicators. These function as signal presence
indicators and verify that the Sense connections back to
the M-5 are made. These indicators will be lit green
whenever signal is present, or will flicker at low signal
levels. These indicators will also light red if there is a
sense fault (amplifier gain not set at +16 dB or sense
lines improperly or not connected).
•Limit indicators. These indicators will come on when-
ever the corresponding limiter is activated, and a moder-
ate amount of flashing of these indicators is acceptable.
The Hi and Lo limiters have an attack time of 100msec.,
so they will not affect peaks in the program material, nor
will they prevent momentary amplifier clipping on peaks.
MultiSense™Driver Protection