The Meyer Sound MM-4CEU is a two-channel, single rack unit, control
electronics unit that provides the required frequency and phase response
correction circuitry tailored to the Meyer Sound MM-4
loudspeaker. Through a SpeakerSense™ connection to the power amplifier
output, the Meyer Sound MM-4CEU continuously monitors the power applied
to the drivers, activating integral peak and RMS limiters to protect against
over-excursion and overheating.
The MM-4CEU is a required component for every MM-4
installation. It performs a number of important signal processing functions
to ensure that the MM-4
meets its published specifications and is protected against damaging overload
conditions.
Frequency and Phase Response Corection
The Meyer Sound MM-4CEU incorporates multiple-pole frequency response
equalization circuitry that is tailored specifically to the Meyer Sound
MM-4
loudspeaker’s acoustical characteristics. This circuitry assures
that the MM-4’s
response remains within ±4 dB from 160 Hz to 16 kHz (free field).
Integral phase response correction circuits maintain a system phase response
of ±45° from 700 Hz to 17 kHz.
The Meyer Sound MM-4CEU also provides an independent front panel low-cut
switch for each signal channel. This switch introduces a high-pass function
that can be used to compensate for low-frequency boost due to half-space
loading in flush-mounted configurations. It can also augment the MM-4
loudspeaker’s headroom when used with a subwoofer for music reproduction.
Driver Protection
The Meyer Sound MM-4CEU features Meyer Sound’s SpeakerSense driver
protection circuitry. Through a connection back from the power amplifier
output, the MM-4CEU’s SpeakerSense function monitors the continuous
and peak power being applied to the MM-4 drivers. Meyer Sound’s
MultiSense function then allows each MM-4CEU channel to monitor two amplifier
outputs, assuring that the protection circuits are activated by the signal
branch with the highest gain. This allows the MM-4CEU to protect the MM-4
in the following ways:
- When the continuous power exceeds the MM-4’s
safe limits, the MM-4CEU introduces an RMS limiter that clamps the audio
signal to protect the MM-4 driver from damage due to overheating.
- When the peak power exceeds the MM-4’s
safe limits, the MM-4CEU introduces a fast-acting peak limiter to clamp
the signal level and protect the MM-4 driver from excessive excursion.
The functions of the SpeakerSense circuitry are indicated on the MM-4CEU
front panel by the following LEDs on each channel.
- Peak Limit - During peak limiting, the Peak Limit
LED glows yellow.
- RMS Limit - During RMS limiting, the RMS Limit LED
glows yellow.
- Sense - When sensing, the MM-4CEU may display one
of two LED colors:
- When the signal is sensed back through the SpeakerSense connection,
the LED glows green.
- When the gain of the amplifier is below 10 dB or above 30 dB,
the LED flashes red, indicating that the protection will not work
properly.
When a channel returns to normal, limiting ceases. The LED for that channel
is inactive, indicating MM-4CEU is not currently limiting.
AC Power
The MM-4CEU accommodates international power standards in two ranges:
90 to 130 V AC and 180 to 260 V AC, 50/60 Hz. A rear-panel switch selects
between the two. |
