Toa AC-M1 User manual

ELECTRONIC
CONTROL UNIT
OPERATING INSTRUCTIONS
AC-M1
CONNECTING PRECAUTIONS
Be sure to provide a power amplifier, 300W or more output to use in connection
with this unit.
Use of less than 300W power amplifier with not maintain primary capabilities and will
lead to failures of the connecting speakers.
The AC-M1 control unit is designed for use exclusively with the SR-M1 and SR-M2
floor monitor speaker systems. Do not use other speakers than the SR-M1 and
SR-M2.
Please follow the instructions in this manual to obtain the optimum results from this unit.
We also recommend you to keep this manual handy for future reference.
TOA Corporation

Contents
User care
General description
Features
Panel facilities
[Front view]
[Rear view]
Connection
Basic block diagram
Back wiring connection with external equipment
Installation
Block diagram
Specifications
Accessories
Appearance
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5
6
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User care
Never disassemble unit and touch the inside or insert metallic stuff into the inside as this may lead to a
breakage or shock hazard.
When water enters, a breakage or shock hazard can be caused. To prevent an accident, immediately
unplug the power cord from the wall AC outlet and contact your nearest TOA dealer.
Wipe unit down with a soft cloth when cleaning the exterior of unit. Never use such volatile liquids as thinner
and benzine because their use may discolor unit.
General description
The AC-M1 control unit is designed for use with the SR-M1 and SR-M2 floor monitor speaker systems.
This electronic control unit provides the channel divider to divide respective frequency range between the
speaker units, and can realize smooth phase characteristics in the speaker system, by according with the
phase in crossover frequency while correcting time lag for the divided frequency range each other between
the speaker units.
In high frequency range in combination with the compression driver and the constant directivity (CD) horn,
the horn equalizer employs to provide smooth phase and amplitude characteristics.
Limiter is provided to prevent the speaker units from over-driven and damage in respective frequency range
and not to arise power amplifier clipping.
Quality sound is realized by use of selected electronic parts as OP amplifier, condensers etc.
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Features
Time lag between speaker units in the speaker system is corrected.
Provided the frequency dividing network function.
Accorded with phase at the crossover frequency.
Limiter is provided to prevent the speaker units from over-driven and damage in each frequency range
and not to arise power amplifier clipping.
An internal equalizer circuit makes the speaker frequency response flat by minimizing the influence of
reflected waves produced when the speaker is directly installed on the floor.
Strictly selected parts and component parts are used for materializing quality sound.
Can be mounted on 19" EIA standard rack. (one size)
Space-saving design, yet dual channel construction. Either the SR-M1 or SR-M2 can be selected in each
channel.
Input and output are used the electronically balanced XLR type connector.
(Pin No.3 : HOT, No.2 : COLD and No.1 : GND)
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Panel facilities
[Front view]
Input level control (INPUT LEVEL 1, 2)
Adjusts the AC-M1 's input level. When adjusting the input level, set this control to maximum position (10),
and the gain control of each power amplifier for woofer and driver unit to 26dB.
Speaker selection switch (MODE)
Set this switch to M1 position when using the SR-M1 speaker, and M2 position when using the SR-M2
speaker.
FC switch indicator
Lights when the FC switch is set to IN.
FC switch (FC)
Makes the speaker frequency response flat by minimizing the influence of reflected waves produced
when the speaker is directly installed on the floor.
Low limit indicator (LOW LIMIT)
Low limit indicator comes on when the low limiter circuit starts to employ with signal of low sense input
terminal. In case the indicator very often flashes, adjust the input level until it occasionally flashes.
High limit indicator (HIGH LIMIT)
High limit indicator comes on when the high limiter circuit starts to employ with signal of high sense input
terminal. In case the indicator very often flashes, adjust the input level until it occasionally flashes.
Low sense input indicator (LOW SENSE)
Low sense input indicator comes on when signal is input to the low sense input terminal.
High sense input indicator (HIGH SENSE)
High sense input indicator comes on when signal is input to the high sense input terminal.
Power indicator
Power indicator comes on when the power switch is ON.
Power switch (POWER)
Press this switch to turn power ON or press it again to turn power OFF.
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[Rear view]
Input connector (INPUT1, 2)
Input connector for signal is used the electronically balanced XLR type connector.
Low output connector (LOW OUT1, 2)
Output connector to the power amplifier for low frequency range is used the electronically balanced XLR
type connector.
High output connector (HIGH OUT 1, 2)
Output connector to the power amplifier for high frequency range is used the electronically balanced XLR
type connector.
Low sense input terminal (LOW SENSE 1, 2)
Input terminal for inputting signal from the power amplifier output for low frequency range is used the
electronically balanced screw terminal.
Connect to accord with polarities between the power amplifier output terminal and the sense input
terminal.
High sense input terminal (HIGH SENSE 1, 2)
Input terminal for inputting signal from the power amplifier output for the high frequency range is used the
electronically balanced screw terminal.
Connect to accord with polarities between the power amplifier output terminal and the sense input
terminal.
Fuse
When the fuse blew, ensure to replace it with the same type fuse after confirming its cause and
countermeasures. (Be sure to unplug the power cord before replacing with a new fuse.)
Use of other fuses than the same type fuse will lead to failures of unit.
Fuse rating
220~240V AC version
120V AC version
250V 0.2A
250V 0.63A
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Connection
Basic block diagram
Back wiring connection of with external equipment
AC-M1
Power amplifier
Mixer/Preamplifier
Mixer/Preamplifier
Power amplifier
7

Installation
FC (Floor Correction) switch
The AC-M1 features the Floor Correction function which minimizes the influence of reflected waves produced
when the speaker is directly installed on the floor.
When a floor monitor speaker is used, direct sound (A) and reflected sound (B) are both heard simultaneously
at the listening point, as shown in Fig. 1, while both sounds are combined into one frequency response. The
reflected sound produces dips (a drop in SPL at the specified frequency) in the frequency response. The AC
-M1 has an internal equalizer to correct the dips for the best possible sound reproduction. Usually set the FC
switch to IN.
Fig. 1
When using the speaker installed on the table (far from the floor) as shown in Fig. 2, set the FC switch to OUT.
Fig. 2
(1) Refer to "Operating instructions of the SR-M1/SR-M2" on connection diagrams with the speakers
and power amplifiers.
(2) When driving two parallel-connected speakers, the amplifier output power must be at least 450W
(at 4 ohm load).
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Block diagram
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Specifications
Model
Input
Input impedance
Rated input level
Max. input level
Sense input
Sense input impedance
Output
Output impedance
Rated output level
Max. output level
Crossover frequency
Distortion
Hum & Noise
Indicators
Front panel operation
Power requirement
Power consumption
Weight
AC-M1
Electronically balanced (Cannon XLR-3-31
or equivalent)
20 (Balanced)
+4dB (Pin No.3 : HOT, No.2 : COLD and No.1 :GND)
+26 dB
Electronically balanced (Binding post)
10
Electronically balanced (Cannon XLR-3-32
or equivalent)
600 (Balanced)
+4dB
+26 dB (Balanced)
1 kHz
Less than 0.05%(+4 dB 1 kHz)
Less than -85 dB (20 Hz~20 kHz)
Power : green LED
FC : green LED
Sense input : green LED (LOW SENSE, HIGH SENSE)
Limit : red LED (LOW LIMIT, HIGH LIMIT)
Input level control
Power switch
Mode switch
FC switch
AC Mains, 50 Hz/60 Hz
18 W (120V AC version)
16 W (220V~240V AC version)
5 kg (11.02 Ib.)
Specifications are subject to change without notice.
0dB=0.775Vrms
Accessories
Fuse (0.63A 120V AC version / 0.2A 220V~240V AC version)
Warranty card (for USA and Canada only)
Operating instructions
1
1
1
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Appearance
11

TOA Corporation
Printed in Japan
133-12-154-80