Operating Instructions
Meyer Sound Laboratories, Inc.
2832 San Pablo Avenue
Berkeley, CA 94702
M-1A
Control
Electronics
Unit
Meyer Sound Laboratories, Inc.
2832 San Pablo Avenue
Berkeley, CA 94702
Operating Instructions
M-1A
Control
Electronics
Unit
Once all the connections have been made
and verified, the system is ready to operate.
■
The M-1A Level control should be set at
minimum.
■
Switch on AC to the M-1A first, then to the
power amplifier.
■
Set the power amplifier level controls (if
any) to maximum.
■
Advance the M-1A Level control to set the
system sensitivity. If the system is not op-
erating properly, recheck all connections.
Operation
Preset Panel Controls
The setup controls on the M-1A Preset Panel
are designed to be used to tailor the system
response for particular applications. Remove
the Preset Panel cover plate to adjust the
controls.
Safe Switch.
The M-1A incorporates three
limiters in the SpeakerSense driver protec-
tion circuitry (see detailed description, below).
When the Safe switch is engaged, the RMS
limiters come on at 6 dB lower power lev-
els, affording added protection when heavy
continuous power demands are placed on
the system. (The VHF peak limiter threshold
is unaffected.) For operator convenience, a
green LED indicator is provided on the M-1A
front panel and when the Safe switch is en-
gaged, this indicator will light.
Note:
It is rec-
ommended that the Safe switch be engaged
until the operator is familiar with the system’s
capabilities.
VHF Switch and Control.
The VHF Switch
affects the very high frequency response of
the system. It selects either a preset (CAL)
high frequency response or variable response
(VAR). In the VAR position, system response
around 16 kHz is adjustable (single-turn
screwdriver adjustment) from +6 dB to -4 dB
around the preset point (CCW for increased
level at 16 kHz). This feature may be used
to emphasize or de-emphasize sibilants,
compensate for room acoustics, etc.
Note:
Because of the difference in high frequency
directivity patterns between the UPA-1C end
the UM-1C UltraMonitor, it is recommended
that the VHF switch be set in the CAL position
for the UM-1C UltraMonitor, and in the VAR
position — with the VAR control fully CCW
— for the UPA-1C.
Lo Cut Switch.
This switch introduces a
6 dB/octave high pass filter at 160 Hz. It is
designed to provide an alternative crossover
slope when using Meyer Sound subwoofers,
but can also be used to compensate for the
proximity effect of cardioid microphones. This
filter is automatically inserted when the Sub
Input is used.
SpeakerSense™
Driver Protection
Through the Sense connections back to the
M-1A from the power amplifiers, the Speak-
erSense circuitry of the M-1A continuously
monitors the voltages across both high and
low frequency drivers. If the amplifier output
exceeds the safe operating limits of the driv-
ers, independent limiters are automatically
activated, holding down the level of the M-
1A’s outputs.
The operation of the SpeakerSense circuitry is
indicated by a set of five LEDs located on the
front panel.
■
Sense Indicators
. These function as sig-
nal presence indicators, and verify that the
Sense connections back to the M-1A are
made. These indicators will be lit whenever
a signal is present, or will flicker at low
signal levels.
■
Limit Indicators
. These indicators will
come on whenever the corresponding lim-
iter is activated and a moderate amount of
flashing of these indicators is acceptable.
The HF and LF limiters have an attack
time of 100 msec, so they will not affect
peaks in the program material, nor will they
prevent momentary amplifier clipping on
peaks.
