Meyer Sound MPS-3 User Manual

MPS-3
Control
Electronics
Unit

The Meyer Sound
MPS-3 is an active sig­nal processor de­signed for use with
Meyer Sound MPS-305
and MPS-355 loud­speakers. It is a ste­reo device, and occu­pies a single 1
rack space. The func­tions of the MPS-3
are:

• Loudspeaker fre­quency and phase
response alignment

• SpeakerSense™ driver
protection

• Low frequency cut for
system equalization

3

/4 -inch

Operating Instructions

Connections

Operation

The MPS-3 operates at line level, and is designed to be the
last component in the signal chain before the power ampli­fier. Connections to the MPS-3 should be made according
to diagram A.

1. Signal Inputs to the MPS-3 should be balanced XLR
male and, for best signal-to-noise ratio, have an average
input level of at least 1 volt RMS. The MPS-3 will accept
peak inputs of up to +26 dBV.

2. SpeakerSense connections are made between the
output of the power amplifier and the MPS-3 Sense inputs.
This connection must be made in order for the
SpeakerSense driver protection circuitry to operate prop­erly. The power amplifier should provide a gain of 26 dB
(±6 dB) for optimum performance.

Once all connections have been made and verified, the
system is ready to operate.

• The MPS-3 Output Level controls should be set at
minimum.

• Switch on AC to the MPS-3 first, then to the power
amplifier.

• Set power amplifier level controls (if any) to maximum.

Note. Polarity of the Sense connections does not matter,
however it is important to verify that these connections are
consistent from Sense input to amp output. (i.e. Channel A
Sense to Amp Channel A output.)

3. Signal Outputs from the MPS-3 are active balanced, at
nominal +4 dBV operating level. The connectors may be
wired balanced or unbalanced, with maximum output levels
before clipping of +26 dBV balanced, +20 dBV unbalanced.

4. Connections between the power amplifier outputs and
the Meyer Sound MPS-305 or MPS-355 loudspeakers
should be made according to the instructions for the loud­speaker. These connections must be verified for correct

polarity.

• Advance the MPS-3 Output Level controls to set
system sensitivities. If the system is not operating
properly, recheck all connections

Note. The Output Level control markings are merely a
visual aid and should not be used to balance two systems.
The output of the MPS-3 is calibrated only when the Output
Level control is fully clockwise.

Meyer Sound Laboratories, Inc.
2832 San Pablo Avenue
Berkeley, CA 94702

MPS-3
Control
Electronics
Unit

Operating Instructions

AC Voltage
Selector and
Fuse

Output Level
Controls and
Mono Switch

Lo Cut Switch

The MPS-3 must have the correct voltage setting and fuse
for the AC power source in your area. To change the AC
voltage setting, first unplug the AC power cord. Using a
small flat-blade screwdriver, move the slide switch to the
appropriate position as indicated by the adjacent panel
legend.

The Output Level Controls regulate the gain of each
channel of the MPS-3. Their range is from off to 0 dB,
with -6 dB gain at the center position.

The Lo Cut switch on the MPS-3 front panel introduces a
6 dB/octave high pass filter at 160 Hz on both channels.
This filter is designed to reduce any low frequency empha­sis caused by corner placement of the MPS-305 or MPS-

Primary protection for the MPS-3 is provided by a 1¦4 A
SloBlo fuse located in a receptacle adjacent to the AC
cord. Before examining or replacing the fuse, first unplug
the AC power cord. To replace the fuse, insert a flat­blade screwdriver in the fuse cap and gently turn counter­clockwise. The fuse will spring from its socket. Replace
only with a fuse of the type and rating specified by Meyer
Sound.

When the Mono Switch is engaged (in), the two input
channels are summed and routed to both outputs. While
operating in mono, each output's level is still controlled by
its respective Level Control. When the Mono Switch is
disengaged (out), the MPS-3 operates in stereo.

355 loudspeakers, but can also be used to compensate
for the proximity effect of cardioid microphones. The Lo
Cut switch is also useful for preventing speaker overload
when using MPS-305 loudspeakers.

SpeakerSense™
Driver Protection

Limiter Operation

Through the Sense connections between the MPS-3 and
the power amplifier, the SpeakerSense circuitry of the
MPS-3 continuously monitors the voltages across the
loudspeaker drivers. If the amplifier ouput exceeds the
safe operating limits of the drivers, either an RMS limiter
or a Peak limiter will be automatically activated, holding
down the power level of the MPS-3 output.

The operation of the SpeakerSense circuitry is indicated
by a single, bi-colored Sense/Limit indicator LED for each
channel .

To verify limiter operation in the field:

• Disconnect loudspeakers, leaving the amplifier and the
MPS-3 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 MPS-3 and the amplifier.

• Switch the Lo Cut out.

The function of the Sense/Limit indicator is as follows:

• Signal Presence Indicator. The Sense/Limit indica-
tor lights green to indicate signal presence, and veri­fies that the Sense connections between the amplifier
and the MPS-3 are made. The indicator will flicker
green at low signal levels.

• Limit Indicator. The Sense/Limit indicator lights red
whenever the limiter is activated. A moderate amount
of red flickering of this indicator is acceptable. The
RMS limiter has an attack time of 60 msec, and is
designed to protect the system in sustained high level
use.

oscillator. If you do not have an oscillator, use a
microphone and a mixer to produce a line-level signal.

• Set the input frequency of the oscillator to 1 kHz, or
whistle into the microphone.

• Bring up the Output Level until you see the Sense/
Limit indicator light red. Since the indicator will light
red only if the limiter actually operates, it provides a
positive indication that the limiter is functioning.

• Supply an input to the MPS-3, preferably a sinewave

Meyer Sound Laboratories, Inc.
2832 San Pablo Avenue
Berkeley, CA 94702