Meyer Sound MTS-4A User Manual

OPERATING INSTRUCTIONS

MTS-4A Self-Powered Loudspeaker Systems

Superior
engineering
for the art
and science

OPERATING INSTRUCTIONS

of sound.



Keep these important operating instructions

Check www.meyersound.com for updates

CONTENTS

Safety Summary 3
The MTS-4A: Introduction 4
AC Power 4
Audio Input 6
Amplification and Protection Circuitry 6
Rigging 7
Measurement and System Integration Tools 8
Complete Systems 8
Driver Troubleshooting 9
Array Design 10
MTS-4A Specifications 12
MTS-4A Dimensions 13
Contact Information 14

SYMBOLS USED

T

HESE SYMBOLS INDICATE IMPORTANT SAFETY OR OPERATING FEATURES IN THIS BOOKLET AND ON THE CHASSIS.

!

Dangerous voltages:

risk of electric shock

Pour indiquer les risques résultant

de tensions dangereuses

Zu die gefahren von

gefährliche spanning zeigen

Para indicar azares provengo

de peligroso voltajes

Important operating

instructions

Pour indequer important

instructions

Zu wichtige betriebs-

anweisung und unter-

haltsanweisung zeigen

Para indicar importante

funcionar y mantenimiento

instrucciones

Frame or chassis

Masse, châssis

Rahmen oder chassis

Armadura o chassis

DECLARATION OF CONFORMITY ACCORDING TO ISO/IEC GUIDE AND EN 45014

The Manufacturer:

EYER SOUND LABORATORIES, INC.

M

2832 San Pablo Avenue
Berkeley, California 94702-2204, USA

Declares that the product:

MTS-4A

Conforms to the following Product Specifications
Safety: EN60065: 1994
EMC: EN55103-1 emmission
EN55103-2 immunity
This device complies with the requirements of the Low Voltage
Directive 73 / 23 / EEC and the EMC Directive 89 / 336
/ EEC.
This device also complies with EN 55103-1 & -2. Operation is
subject to the following two conditions:
(1) this device may not cause harmful interference, and
(2) this device must accept any interference received, including

interference that may cause undesired operation.

1

2

E

NVIRONMENTAL SPECIFICATIONS FOR MEYER SOUND ELECTRONICS PRODUCTS:

Operating Temperature

Nonoperating Temperature

Humidity

Operating Altitude

Nonoperating Altitude

0° to + 45°
<-40°C or > +75°C
to 95% at 35°C
to 4600 m (15,000 ft)
to 6300 m (25,000 ft)
30g 11 msec half-sine on each

Shock

of 6 sides

Vibration

10Hz to 55Hz (0.010m
peak-to-peak excursion)

Protective earth ground

Terre de protection

Die schutzerde

Tierra proteccionista

3K59 COMMERCIAL

AUDIO SYSTEM

Made by Meyer Sound Laboratories
Berkeley, California USA

European Office:
Meyer Sound Lab. GmbH
Carl Zeiss Strasse 13
56751 Polch, Germany

N757 MTS-4A

Office of Quality Manager
Berkeley, California USA Dec 22, 2000

2

!

SAFETY SUMMARY

ENGLISH

• To reduce the risk of electric shock,
disconnect the unit from the AC
mains before installing audio cable.
Reconnect the power cord only after
making all signal connections.

• Connect the unit to a two-pole, three
wire grounding mains receptacle. The
receptacle must be connected to a
fuse or circuit breaker. Connection to
any other type of receptacle poses a
shock hazard and may violate local
electrical codes.

• Do not allow water or any foreign
object to get inside the unit. Do not
put objects containing liquid on, or
near, the unit.

• To reduce the risk of overheating
the unit, avoid exposing it to direct
sunlight. Do not install the unit near
heat-emitting appliances, such as a
room heater or stove.

• This unit contains potentially
hazardous voltages. Do not attempt
to disassemble the unit. The unit
contains no user-serviceable parts.
Repairs should be performed only by
factory-trained service personnel.

RANÇAIS

F

• Pour réduire le risque d’électrocution,
débrancher la prise principale de
appareil, avant d’installer le câble
d’interface allant à l’audio. Ne
rebrancher le bloc d’alimentation
qu’après avoir effectué toutes les
connections.

• Branchez appareil dans une prise de
courant à 3 dérivations (deux pôles et
la terre). Cette prise doit être munie
d’une protection adéquate (fusible ou
coupe-circuit). Le branchement dans
tout autre genre de prise pourrait
entraîner un risque d’électrocution et
peut constituer une infraction à la
réglementation locale concernant les
installations électriques.

• Ne pas laisser de l’eau ou tout objet

pénétrer dans appareil. Ne pas placer
de r´cipients contenant un liquide sur
cet appareil, ni à proximité de celui­ci.

• Pour éviter une surchauffe de
appareil, conserver-la à l’abri du
soleil. Ne pas installer à proximité
d’appareils dégageant de la chaleur
tels que radiateurs ou appareils de
chauffage.

• Ce appareil contient des circuits haute
tension présentant un danger. Ne
jamais essayer de le démonter. Il
n’y a aucun composant qui puisse
être réparé par l’utilisateur. Toutes
les réparations doivent être effectuées
par du personnel qualifié et agréé par
le constructeur.

D

EUTSCH

• Um die Gefahr eines elektrischen
Schlages auf ein Minimum zu
reduzieren, den Gerät vom Stromnetz
trennen, bevor ggf. ein
Audio-Schnittstellensignalkabel
angeschlossen wird. Das Netzkabel
erst nach Herstellung aller
Signalverbindungen wieder
einstecken.

• Der Gerät an eine geerdete zweipolige
Dreiphasen-Netzsteckdose
anschließen. Die Steckdose muß
mit einem geeigneten Abzweigschutz
(Sicherung oder Leistungsschalter)
verbunden sein. Der Anschluß der
unterbrechungsfreien Stromversorgung
an einen anderen Steckdosentyp kann
zu Stromschlägen führen und gegen
die örtlichen Vorschriften verstoßen.

• Darauf achten, daß weder Wasser
noch Fremdkörper in das Innere den
Gerät eindringen. Keine Objekte, die
Flüssigkeit enthalten, auf oder neben
die unterbrechungsfreie
Stromversorgung stellen.

• Um ein Überhitzen dem Gerät zu
verhindern, das Gerät vor direkter
Sonneneinstrahlung fernhalten und

nicht in der Nähe von
wärmeabstrahlenden Haushaltsgeräten
(z.B. Heizgerät oder Herd) aufstellen.

• Im Inneren diesem Gerät herr-schen
potentiell gefährliche Spannungen.
Nicht versuchen, das Gerät zu öffnen.
Es enthält keine vom Benutzer
reparierbaren Teile. Reparaturen
dürfen nur von ausgebildetem
Kundenienstpersonal durchgeführt
werden.

E

SPAÑOL

• Para reducir el riesgo de descarga
eléctrica, desconecte de la red el
aparato antes de instalar el cable de
señalización de interfaz de la segnale.
Vuelva a conectar el conductor
flexible de alimentación solamente
una vez efectuadas todas las
interconexiones de señalizatción.

• Conecte el aparato a un tomacorriente
bipolar y trifilar con neutro de
puesta a tierra. El tomacorriente
debe estar conectado a la protección
de derivación apropiada (ya sea un
fusible o un disyuntor). La conexión
a cualquier otro tipo de tomacorriente
puede constituir peligro de descarga
eléctrica y violar los códigos
eléctricos locales.

• No deje que en el aparato entre agua
ni ningún objeto extraño. No ponga
objetos con líquidos encima de la
unidad ni cerca de ella.

• Para reducir el riesgo de
sobrecalentamiento, no exponga la
unidad a los rayos directos del sol
ni la instale cerca de artefactos que
emiten calor, como estufas o cocinas.

• Este aparato contiene niveles de voltaje
peligrosos en potencia. No intente
desarmar la unidad, pues no contiene
piezas que puedan ser repardas por
el usuario. Las reparaciones deben
efectuarse únicamente por parte del
personal de mantenimiento capacitado
en la fábrica.

3

THE MTS-4A: INTRODUCTION

The Meyer MTS-4A self-powered loudspeaker is a compact,
self-contained, full-range system suited for clubs and small
theatres (throw distances less than 100 ft). Its trapezoidal
shape facilitates array design that maximizes coverage and
SPL for the size of the array. Since all frequencies are produced
from one cabinet, the MTS-4A better approximates a point­source radiator, creating a smoother frequency image than
separate mid-hi and subwoofer cabinets. The MTS-4A can be
used as a PA, front-fill, bass, and keyboard speaker, and as a
side-fill and drum monitor.

The MTS-4A contains independent amplifier and control
electronics for three low frequency cone drivers (18”, 15”,
12”), and one high frequency horn driver (4” diaphragm,
2” throat). Each driver is contained in a separate vented

AC POWER

enclosure. This integrated design improves performance,
durability, and reliability, eliminates amplifier racks, and
simplifies setup and installation. The MTS-4A has the
following acoustical specifications:

Frequency Response ±3 dB 30 Hz – 16 kHz
Phase Response ±70° 90 Hz – 17.2 kHz
Coverage 70° H x 60° V
Dynamic Range >110 dB

See 12 for complete specifications.

The MTS-4A can be equipped to operate with the Remote

Monitoring System (RMS)

application.

1

interface network and software

When AC power is applied to the MTS-4A, the Intelligent AC™
supply automatically selects the correct operating voltage,
allowing the MTS-4A to be used in the US, Europe, or Japan
without manually setting a voltage switch. The Intelligent AC
power supply also performs surge suppression for high voltage
transients (up to 275 V), minimizes inrush current, and filters
EMI. Continuous voltages above 275 VAC may damage the
unit! The MTS-4A uses a NEMA L6-20P or IEC 309 male power
inlet and satisfies UL, CSA, and EC safety standards.

VOLTAGE REQUIREMENTS

The MTS-4A operates safely and without audio discontinuity if
the AC voltage stays within the ranges 85–134 V or 165–264
V, at 50 or 60 Hz. Immediately after applying AC power, the
green Active LED on the user panel illuminates and the proper
operating voltage is automatically selected, but the system is
muted. During the next three seconds, the primary fan turns
on, the main power supply slowly ramps on, and the system is
enabled to pass audio signals.

NOTE: If the Active LED does not illuminate or the system

does not respond to audio input after ten seconds,
remove AC power to avoid possible damage to the unit.
Experienced electronics technicians with access to a
test bench can verify proper operation for the power
supply and amplifier system with The Meyer Sound
Self-Powered Series MP-2 and MP-4 Field Verification
Procedure (part # 17.022.066.01; contact Meyer Sound
to receive this document). All other users should
contact Meyer Sound or an authorized Meyer service
center.

If the voltage decreases below the lower bound of either
operating range (known as a brown-out period), the supply
uses current from its storage circuits and continues to
function briefly. The unit turns off if the voltage does not
increase above the threshold before the storage circuits are
depleted. The length of time that the MTS-4A continues to
operate during brown-out depends on how low the voltage
drops and the audio source level during this period.

If the voltage fluctuates within either operating range,
automatic tap selection stabilizes the internal operating
voltage. This tap selection is instantaneous and there are no
audible artifacts. If the voltage increases above the upper
bound of either range, the power supply turns off rapidly,
preventing damage to the unit.

If the MTS-4A shuts down due to either low or high voltage,
the power supply automatically turns on after three seconds if
the voltage has returned to either normal operating range. If
the MTS-4A does not turn back on after ten seconds, remove
AC power and refer to the Note above.

NOTE: We recommend that the power supply be operated

at least a few volts away from the upper and lower
bounds of the operating windows to avoid brown-out
and possible shutdown.

CURRENT REQUIREMENTS

The MTS-4A presents a dynamic load to the AC mains which
causes the amount of current to fluctuate between quiet and
loud operating levels. Since different types of cables and

1. RMS displays signal and power levels, driver and cooling fan status,
limiter activity, and amplifier temperature for all speakers in the
network on a Windows-based PC. Contact Meyer Sound for more
information about RMS.

4

circuit breakers heat up (and trip) at varying rates, it is
essential to understand the types of current ratings and how
they correspond to circuit breaker and cable specifications.

The maximum continuous RMS current is the maximum RMS
current over a duration of at least 10 seconds. It is used to
calculate the temperature increase in cables, which is used
to select cables that conform to electrical code standards.
It is also used to select the rating for slow-reacting thermal
breakers.

The maximum burst RMS current is the maximum RMS
current over a one second duration. It is used to select the
rating for most magnetic breakers.

The maximum instantaneous peak current during burst is
used to select the rating for fast-reacting magnetic breakers
and to calculate the peak voltage drop in long AC cables
according to the formula

Vpkdrop = Ipk x Rtotal cable

Use the table below as a guide to select cables and circuit
breakers with appropriate ratings for your operating voltage.

V511V032V001

If the colors referred to in the diagram don't correspond to the
terminals in your plug, use the following guidelines:

• Connect the blue wire to the terminal marked with an N
or colored black.

• Connect the brown wire to the terminal marked with an L
or colored red.

• Connect the green and yellow wire to the terminal marked
with an E (or ) or colored green (or green and yellow).

SAFETY ISSUES

Pay close attention to these important electrical and safety
issues.

Use a power cord adapter to drive the MTS-4A

from a standard 3-prong outlet (NEMA 5-15R; 125
V max).

blue =
neutral

yellow/green =
earth ground
(chassis)

brown = hot

SMRsuounitnoC.xaMA14 A7A16

SMRtsruB.xaMA26 A31A30

tsruBgniruDkaePx.aMA83A18 A42

The minimum electrical service amperage required by a system
of Meyer speakers is the sum of their maximum continuous
RMS currents. We recommend allowing an additional 30%
above the minimum amperage to prevent peak voltage drops
at the service entry.

Note: In the unlikely case that the circuit breakers trip

(the white center buttons pop out), do not reset the
breakers! Contact Meyer Sound for repair information.

POWER CONNECTOR WIRING CONVENTIONS

Use the following AC cable wiring diagram to create
international or special-purpose power connectors:

earth
ground

chassis
ground

The MTS-4A requires a grounded outlet. Always use a

grounding adapter when connecting to ungrounded
outlets.

Do not use a ground-lifting adapter or cut the AC

cable ground pin.

Keep all liquids away from the MTS-4A to avoid hazards from
electrical shock.

Do not operate the unit if the power cables are frayed or
broken.
Tie-wrap anchors on the amplifier chassis provide strain relief
for the power and signal cables. Insert the plastic tie-wraps
through the anchors and wrap them around the cables.

AC cable color code

5

AUDIO INPUT

The MTS-4A presents a 10 kΩ balanced input impedance to a
three-pin XLR connector wired with the following convention:

Pin 1 220 kΩ to chassis and earth ground (ESD clamped)
Pin 2 Signal
Pin 3 Signal
Case Earth (AC) ground and chassis

with XLR connectors for balanced signal sources.

NOTE: If abnormal noise (hum, hiss, popping) is produced from

the loudspeaker, disconnect the audio source from the
speaker. If the noise stops, then the problem is not
within the loudspeaker; check the audio input and AC
power.

Shorting an input connector pin to the case can

form a ground loop and cause hum.

Pins 2 and 3 carry the input as a differential signal; their
polarity can be reversed with the input polarity switch on the
user panel. If the switch is in the up position, pin 2 is hot
relative to pin 3, resulting in a positive pressure wave when a
positive signal is applied to pin 2. Use standard audio cables

AMPLIFICATION AND PROTECTION CIRCUITRY

Each driver in the MTS-4A is powered by one channel of the
Meyer MP-4, a four-channel 2480 W amplifier (620 W/ch)
utilizing complementary power MOSFET output stages (class
AB/H). The following sections discuss the MP-4’s limiting
circuitry and the four-fan cooling system.

TRUPOWER™ LIMITING SYSTEM

Conventional limiters assume that the resistance of a speaker
remains constant and set the limiting threshold by measuring
voltage only. This method is inaccurate because the speaker’s
resistance changes in response to the frequency content
of the source material and thermal variations in the
speaker’s voice coil and magnet. Conventional limiters begin
limiting prematurely, which under-utilizes system headroom
and deprives the speaker of its full dynamic range.

A single source can drive multiple MTS-4As with a paralleled
input loop, creating an unbuffered hardwired loop connection.
Make certain that the source equipment can drive the total
load impedance presented by the paralleled input circuit. For
example, since the input impedance of a single MTS-4A is
10 kΩ, cascading 20 MTS-4As produces a balanced input
impedance of 500Ω. If a 150Ω source is used, the 500Ω load
results in a 2.28 dB loss.

is hard limiting with these negative consequences:

• Increasing the input level will not increase the volume.

• The system distorts due to clipping and nonlinear driver

operation.

• Unequal limiting between the drivers alters the frequency
response.

• Driver and amplifier components are subjected to maximum
heat, which shortens their life-span.

The TPL LEDs can indicate an imbalance in a system of
speakers by functioning like a spectrum analyzer. If speakers
in a subwoofer, mid-bass, or mid-hi subsystem begin to limit
before reaching the required operating level for the entire
system, then that subsystem needs to be supplemented with
additional speakers.

The TruPower limiting (TPL) system accounts for varying
speaker impedance by measuring current, in addition to
voltage, to compute the power dissipation and voice coil
temperature. TPL improves performance before and during
limiting by allowing the speaker to produce its maximum SPL
across its entire frequency range. TPL also extends the lifetime
of the drivers by controlling the temperature of the voice coil.
Sub Limit, Lo Limit, Mid Limit, and Hi Limit LEDs on the
user panel indicate TPL activity for each of the four amplifier
channels. When any channel exceeds the safe continuous
power level, that channel’s limiter engages, ceasing operation
when the power level returns to normal. The limiters for each
channel function independently and do not affect the signal
when the LEDs are inactive.

The MTS-4A performs within its acoustical specifications and
operates at a normal temperature if a given TPL LED is on for
no longer than two seconds, and off for at least one second. If
an LED remains on for longer than three seconds, that channel

NOTE: Although the TPL limiters exhibit smooth sonic

characteristics, we do not recommend using them
for intentional compression effects. Use an outboard
compressor/limiter to compress a mixed signal.

FANS AND COOLING SYSTEM

The MTS-4A uses a forced-air cooling system with four fans
to prevent the amplifiers from overheating. The fans draw
air in through ducts on the front of the cabinet, over the
heatsinks, and out the rear of the cabinet. Since dust does not
accumulate in the amplifier circuitry, its life-span is increased
significantly.

A foam insert filter, in combination with the entire front grill
surface, acts as an air filter for the cooling system. Despite
the filtering, extensive use or a dusty operating environment
can allow dust to accumulate along the path of the
airflow, preventing normal cooling. We recommend periodically
removing the grill, filter, and amplifier module and using

6

compressed air to clear dust from the grill, filter, fans, and
heatsinks. Make sure that the air ducts are clear and that
there is at least six inches clearance for exhaust behind the
cabinet.

Two variable-speed primary fans run continuously with an
inaudible operating noise of 22 dBA at 1 m at their slowest
speed. When the temperature of the heatsinks reaches 42°C,
the primary fans begin increasing their speed, reaching full
speed at 62°C . At full speed, they are barely audible near the
cabinet, even without an audio signal.

In the unusual event that the heatsink temperature reaches
74°C, the secondary fans turn on; they turn off when the
temperature decreases to 68°C. The secondary fans are audible

RIGGING

The MTS-4A weighs 280 lb (127 kg). The maximum
recommended load for a single cabinet with aircraft pan
fittings is 600 lb (273 kg). This working load is based on a
5:1 safety factor. The MTS-4A has five rigging brackets (three
on top, two on bottom). Each bracket is capable of supporting
the full working load of the cabinet.

rigging brackets

(three on top, two on bottom)

at close proximity without an audio signal and turn on in
response to

• primary fan failure (check its status immediately);

• accumulation of dust in the cooling system path;

• a prolonged period of high source levels in hot

temperatures or direct sunlight;

• driver failure.

Troubleshooting Note: In the highly unlikely event that the
secondary fans do not keep the temperature below 85°C, the
MTS-4A automatically shuts down until AC power is removed
and reapplied. If the MTS-4A shuts down again after cooling
and reapplying AC power, contact Meyer Sound for repair
information.

Rigging load ratings assume a straight tensile pull and that
the cabinet is in new condition with aircraft pan fittings. If
these conditions are not met, the load ratings can be
reduced significantly. Load ratings can also be reduced by
age, wear, and damage. It is important to inspect the rigging
hardware regularly and replace worn or damaged components
immediately.

The cabinet, exposed electronic circuitry, and drivers can
receive protective treatment that permits safe use in wet
conditions. Additionally, a rain hood can be fitted to shield
cables and electronics. Do not install a unit outdoors
without weather protection! Contact Meyer Sound for more
information.

Handles are for carrying only.
Do not use them for rigging!

There are four types of interchangeable rigging brackets, each
fastened by six Phillips screws:

• aircraft pan fittings (ring and stud)

• 3/8”-16 nut plates

• M-10 x 1.5 metric nut plates

• blank plates (if no rigging brackets are requested)

Note: Units with nut plates are rated for the weight of one

cabinet only.

Note: All Meyer Sound products must be used in accordance

with local, state, federal, and industry regulations.
It is the owner’s and/or user’s responsibility to
evaluate the reliability of any rigging method for their
application. Rigging should be done only by experienced
professionals.

7

MEASUREMENT AND SYSTEM INTEGRATION TOOLS

It is essential that even the most carefully assembled sound
systems be analyzed with precise measurement tools. We
recommend using the Meyer Sound SIM® System II Sound

Analyzer

• assist the process of choosing and configuring speakers;

• measure propagation delays between subsystems to set the

• measure and equalize variations in frequency response

Contact Meyer Sound for assistance with your application.
We recommend using one of the Meyer Sound line drivers to
integrate different types of Meyer self-powered speakers into
a complete system. The LD-1A and LD-2 have two channels
equipped to control a full-range main system, and the LD-1A
has six auxiliary channels for down-fill, front-fill, and delay
systems. The LD-1A maintains signal integrity for long cable
paths and provides the following useful functions:

• The Lo Cut switch activates a high-pass filter (160 Hz, –12

1

and CP-10 Parametric Equalizer2 to

correct polarity and delay times;

caused by the acoustical environment and the placement
and interaction of speakers.

dB/oct, Q = 0.8) that performs a crossover function for the
Mid-Hi output.

• The DS-2 & Sub Crossover switch (channels 1 and 2 only)
activates a crossover network optimized for the DS-2P or
DS-4P when used with the 650-P. With the switch in,
frequencies below 80 Hz are sent to the Sub output (for
the 650-P), and above 80 Hz to the DS-2 output. When
the 650-P is used without the DS-2P or DS-2P, the switch
should be out, which sends a full-range signal to both the
DS-2 and Sub outputs.

• The DS-2 f and Sub f switches (channels 1 and 2 only)
toggle the polarity for the DS-2 and Sub outputs.

• The Mid-Hi, DS-2, and Sub outputs (channels 1 and 2 only)
each have their own gain control and mute switch.

POLARITY NOTE: The polarity for Meyer Sound self-powered
speakers may be reversed using the input polarity switch on
the user panel. The line drivers also allows polarity reversal
with the DS-2 f and Sub f switches for speakers connected
to the DS-2 and Sub outputs. When making polarity decisions
in applications that include the LD-1A or the LD-2, check the
state of all polarity switches.

COMPLETE SYSTEMS

MEYER SPEAKER TYPES

The following Meyer speakers are mentioned in the example
applications.

CQ Self-powered mid-hi speaker
PSW-4 Self-powered subwoofer
650-P Self-powered subwoofer

The Meyer self-powered speakers listed above have a loop
connection to send the input signal to another speaker.
Full-range signals can be applied to all Meyer self-powered
subwoofers because they have built-in active crossovers that
filter mid-hi frequencies.

MTS-4A AND PSW-4

Combining the PSW-4 with the MTS-4A doubles the low
frequency power of the system because both loudspeakers
contain the same sub and low drivers. Due to the summation
between the PSW-4 and the MTS-4A, the system frequency

1. The Meyer Sound SIM II is a computer-based dual channel FFT
analysis system optimized for electroacoustic measurement.

response exhibits a rise in the range 30–160 Hz. It is
important to emphasize that the speakers are in phase in
this region. This rise can be corrected using the Meyer CP-10
Parametric Equalizer, if desired.

CP-10 EQ

(1 Channel)

input

loop

MTS-4A

PSW-4

The LD-1A/2 with an MTS-4A and PSW-4

Set the MTS-4A and PSW-4 to the same polarity.

2. The CP-10 is a dual-channel, complimentary phase, precision analog
equalizer with five bands of parametric equalization and two bands
of shelving filters.

8

LD-1A WITH FLOWN MTS-4A AND CQ; 650-P ON THE
FLOOR

This example shows the LD-1A integrating a complete system
of self-powered speakers for a large venue. Although channels
1, 3, and 5 constitute half of the system, channels 2, 4, and
6 can be used with identical connections to create the other
half. The upper and lower MTS-4A arrays and CQ down-fills are
flown; the 650-P subwoofers are on the floor.

MTS-4A Upper System

LD-1A

CH 1

Input Mid-Hi

Output

Sub

Output

Input Output

CH 3

Input Output

CH 5

MTS-4A Lower System

CQ Down-fills

650-P Subwoofers

Delay

A

B

Ch A

CP-10 EQ

Ch B

CP-10 EQ

The CH 1 Mid-Hi and CH 3 outputs drive the upper and lower
MTS-4A arrays, respectively, applying appropriate levels for
speakers directed at different distances. CH 3 is delayed to
phase align the upper and lower systems in the intersecting
coverage area.

Since the MTS-4A arrays are driven by full-range signals, the
Lo Cut switches for the CH 1 Mid-Hi and CH 3 outputs should
be out. The Array EQ switches should also be out because the
Array EQ filter is designed for the MSL-4, not the MTS-4A.
Since the DS-P Series is not included in this system, the DS-2
& Sub Crossover switch should be out.

CH 5 controls the CQ down-fill system. Since the main system
is more powerful than the down-fill system to project farther
into the venue, the main system is audible in the down-fill’s
coverage area. To insure that the systems combine properly
in this area:

• Set the CQ to the opposite polarity to the MTS-4A to phase
align the mid-hi frequencies and minimize the MTS-4A’s low
frequency down-lobe.

• Use the CH 5 Lo Cut filter to eliminate the low frequency
rise caused by the overlap with the 650-P/MTS-4A systems.

• Delay the down-fill to align with the MTS-4A system in
their intersecting coverage area.

The LD-1A with MTS-4As, CQs, and 650-P Subwoofers

Set the MTS-4A and CQ to the same polarity. The polarity
for the 650-P depends on the distance of the measurement
position from the flown and subwoofer systems.

DRIVER TROUBLESHOOTING

TROUBLESHOOTING WITH TPL

The TPL LED can indicate serious driver problems, if
interpreted correctly. If one MTS-4A in a system exhibits
substantially more TPL activity than others receiving the same
audio signal, then one or both drivers in that unit may have a
short circuit. This is a potentially dangerous condition for the
electronics; shut the MTS-4A down immediately.

The TPL circuit does not activate if there is no power
dissipation in the driver, regardless of the input signal level.
Therefore, if all MTS-4As in a system receiving the same audio
signal exhibit TPL activity except one, then that unit may
have an open voice coil; disconnect it and contact Meyer
Sound for repair information.

NOTE: The Remote Monitoring System (RMS) provides precise

information about peak power, peak voltage, and
average voltage (VU) for each amplifier channel,
enabling a more complete driver diagnostic than the

The polarity of the 650-P depends on the height and
distance of the measurement position from the flown and
subwoofer systems. The entire system should be measured,
phase-aligned, and equalized using the SIM System II Sound
Analyzer and CP-10 Parametric Equalizer.

TPL LEDs. Contact Meyer Sound for more information
about RMS.

DRIVER REPLACEMENT

To determine whether the high or low drivers are functioning
properly, or replace a damaged driver, contact Meyer Sound to
obtain The Low Driver Inspection and Evaluation Procedure

for Self-Powered Series Products (part # 17.010.120.01) or
The High Driver Inspection and Evaluation Procedure for
Self-Powered Series Products (part # 17.010.120.02).

VERIFYING DRIVER POLARITY

Incorrect driver polarity impairs system performance and may
damage the drivers. All Meyer loudspeakers are shipped with
the drivers in correct alignment. However, if the driver or
circuit wiring has been removed or disassembled in any
loudspeaker in a system for any reason, it is essential to check
the polarity between drivers in the same cabinet and between
adjacent loudspeakers.

9

We do not recommend using phase poppers to analyze driver
polarity. The phase response for all drivers varies, to some
degree, over the frequency range in which it operates. Since
the phase popper, a popular but inaccurate tool, does not
discern variations in phase response with respect to frequency,
it provides no useful information about the phase response
through the crossover, the most important consideration for
determining correct driver polarity.

Phase poppers are, therefore, not useful for performing phase
measurements on an individual loudspeaker or a full-range
sound system containing one or more crossovers. If necessary,
apply a phase popper only to loudspeakers with identical
drivers without a crossover, and check the system’s overall
phase response with a frequency analyzer and/or listening
test.

NOTE: Since polarity reversal causes excessive driver excursion

at high source levels, use moderate levels for these
tests.

DRIVER POLARITY IN THE SAME LOUDSPEAKER

Use the following test procedure to verify polarity between
drivers in the same loudspeaker:

1. Place a measurement microphone 3 ft from the front of
the loudspeaker at the midway point between the 12” and
15” drivers.

2. Connect a signal source to the loudspeaker and note the
frequency response.

The polarity is correct if the frequency response is smooth
through each crossover region (40 Hz, 100 Hz, 1 kHz).
Cancellation greater than 6 dB in any region indicates polarity
reversal between the drivers on either side of that crossover
point.

POLARITY BETWEEN ADJACENT LOUDSPEAKERS

Use the following test procedure to verify the polarity
between two adjacent loudspeakers of the same type:

1. Position two loudspeakers adjacent to each other.

2. Place a measurement microphone 3 ft from the speakers on
the axis between them.

3. Connect a signal source to one speaker and note the
frequency response and overall level.

4. Apply the same signal to the second speaker with the first
speaker still connected.

The polarity is correct if the frequency response remains
constant with a significant increase in amplitude. Broadband
cancellation (decreased overall level) indicates polarity
reversal.

NOTE: Polarity tests among more than two speakers may

damage the drivers in the cabinet with reversed
polarity.

This driver is 180 out of
phase to the other drivers

Drivers with correct
polarity cause acoustic
addition

Drivers with reversed
polarity cause acoustic
cancellation

ARRAY DESIGN

BACKGROUND

Creating an effective array with the MTS-4A requires a precise
understanding of how to combine the coverage area and SPL
of the individual speaker with those of adjacent speakers.
Array design is a trade-off between increasing on-axis power
and creating smooth transitions between the coverage areas
of adjacent speakers.

As the splay angle (the angle between adjacent cabinet faces)
decreases below the coverage angle of the individual speaker,
the on-axis power increases, but the coverage overlap between
adjacent speakers causes comb filtering and other frequency
response variations.

As the splay angle increases toward the coverage angle,
the on-axis power decreases, but the variations in frequency
response diminish. As the splay angle increases beyond the
coverage angle, noticeable gaps begin to form in the array’s
coverage area.

NOTE: The trapezoidal shape of the MTS-4A does not represent

the horizontal coverage area of the speaker. Tight­packing MTS-4As results in the minimum recommended
splay angle (15°) for horizontal arrays.

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ARRAY DESIGN FOR LOW FREQUENCIES

Since the MTS-4A contains sub and low frequency drivers, in
addition to mid and high drivers, array design for the MTS-4A
must incorporate the different array response of high and low
frequencies. The beam width for a single speaker widens as
the frequency decreases. Frequencies below 125 Hz are mostly
omnidirectional while higher frequencies are more directional.

NOTE: H and V are abbreviations for horizontal and vertical.

(without a nearby wall or ceiling) do not. In general,
subwoofers in half-space generate twice the SPL (+6 dB)
compared to the same number in free-space.

NOTE: SPL values refer to an on-axis measurement position.

The actual SPL addition and narrowing of coverage
varies with frequency and depends on the physical
displacement between cabinets, loading conditions, and
room acoustics.

The low frequencies of adjacent arrayed speakers exhibit
on-axis addition and off-axis cancellation, resulting in a
narrowing of coverage in the dimension in which they are
arrayed. A H array of two MTS-4As narrows the H coverage
without affecting the V coverage. A V array of two MTS-4As
narrows the V, without affecting the H coverage. In both
cases, there is 3 to 6 dB SPL of on-axis low frequency (LF)
addition compared to a single MTS-4A. Due to the larger
distance between LF drivers in V, compared to H arrays, the
V coverage narrows at a faster rate than does the H coverage
for H arrays, given the same array size and adjacent speaker
placement.

Increasing the number of MTS-4As in the array increases the
LF directional control. A properly designed V array steers
low frequencies to include balconies and upper tiers, while
a H array focuses low frequencies for longer throw distances
without interacting with the walls.

LOADING

One of the most important factors governing LF response is
speaker placement with respect to adjacent surfaces. The MTS­4A gains significant LF power by coupling with nearby floors
and walls. Half-space loading describes a speaker coupling
with one surface. Speakers placed on the floor benefit
from half-space loading, while flown speakers in free-space

MTS-4A COVERAGE AND MAXIMUM SPL

A series of outdoor tests was conducted at Meyer Sound to
determine the coverage angle and on-axis SPL for arrays with
one and two horizontal rows of up to five speakers each, at
numerous splay angles. The measurements were conducted at
a distance of 8 m with half-space loading; on-axis SPL values
were interpolated from 8 to 1 m. The coverage angle for the
array is the result of averaging the –6 dB points from 125
Hz to 8 kHz.

The horizontal angles in the tables below represent the
optimal narrow (15°), middle (30°), and wide (45°)
orientations for the MTS-4A. The vertical splay angles
represent the optimal narrow and wide configurations. 2@0°
LT denotes long throw: the two horns are coupled directly
together (top speaker upside down/bottom speaker upright) to
form a single narrow horn.

The table on this page shows the SPL and coverage angles
that result from grouping the MTS-4A in arrays of up to five
units horizontally and two rows vertically. All splay angles
refer to the angle between cabinet centers.

If this information does not address your application
requirements, contact Meyer Sound to obtain additional
information on array design.

MTS-4A Array Coverage and Maximum SPL

Number of Horizontal

MTS-4As @ Angle

Vertical Rows of MTS-4As

@ Angle

1 70˚ 60˚ 140 50˚ 60˚ 146 60˚ 60˚ 145 100˚ 60˚ 142 80˚ 60˚ 149 120˚ 60˚ 147 150˚ 60˚ 145

2 @ 0˚ (LT) 7 0˚ 30˚ 14 6 50 ˚ 30˚ 1 52 6 0˚ 30 ˚ 15 1 100˚ 30 ˚ 148 80 ˚ 30˚ 1 55 12 0˚ 3 0˚ 1 53 15 0˚ 3 0˚ 151

2 @ 15˚ 7 0˚ 50 ˚ 14 5 5 0˚ 50 ˚ 15 1 6 0˚ 50 ˚ 1 50 10 0˚ 5 0˚ 1 47 80˚ 5 0˚ 1 54 12 0˚ 5 0˚ 152 15 0˚ 5 0˚ 150

2 @ 30˚ 7 0˚ 90 ˚ 14 3 5 0˚ 90 ˚ 14 9 6 0˚ 90 ˚ 1 48 10 0˚ 9 0˚ 1 45 80˚ 9 0˚ 1 52 12 0˚ 9 0˚ 150 15 0˚ 9 0˚ 148

Number of Horizontal

MTS-4As @ Angle

Vertical Rows of MTS-4As

@ Angle

1 100˚ 60˚ 151 140˚ 60˚ 148 190 60˚ 146 110˚ 60˚ 153 180˚ 60˚ 148 240 60˚ 146

2 @ 0˚ (LT) 100 ˚ 3 0˚ 1 57 140˚ 30˚ 154 190 30˚ 152 110˚ 30˚ 159 180˚ 30˚ 154 240 30˚ 152

2 @ 15˚ 100 ˚ 50˚ 1 56 14 0˚ 5 0˚ 153 19 0 50˚ 15 1 1 10˚ 50 ˚ 15 8 1 80˚ 50 ˚ 15 3 2 40 5 0˚ 1 51

2 @ 30˚ 100 ˚ 90˚ 1 54 14 0˚ 9 0˚ 151 19 0 90˚ 14 9 1 10˚ 90 ˚ 15 6 1 80˚ 90 ˚ 15 1 2 40 9 0˚ 1 49

1 2 @ 15˚ 2 @ 30˚ 2 @ 45˚ 3 @ 15˚ 3 @ 30˚ 3 @ 45˚

Coverage Max Peak Coverage M ax Peak Coverage Max Peak Coverage Max Peak Coverage Max Peak Coverage Max Peak Coverage Max Peak

H V dB SPL H V dB SPL H V dB SPL H V dB SPL H V dB SPL H V dB SPL H V dB SPL

4 @ 15˚ 4 @ 30˚ 4 @ 45˚ 5 @ 15˚ 5 @ 30˚ 5 @ 45˚

Coverage Max Peak Coverage M ax Peak Coverage Max Peak Coverage M ax Peak Coverage Max Peak Coverage Max Peak

H V dB SPL H V dB SPL H V dB SPL H V dB SPL H V dB SPL H V dB SPL

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MT S-4A SPECIFICATIONS

Acoustical

(each loudspeaker)

Coverage

Transducers

Audio Input

Amplifiers

AC Power

Max Continuous RMS Current (>10 sec)

1

Operating Frequency Range

Half-Space

Phase Response

Maximum Peak SPL

Signal to Noise Ratio

Sub Frequency

Low Frequency

Mid Frequency

High Frequency

Nominal Input Level

Burst capability

THD, IM, TIM

Automatic voltage selection

Operational Voltage Range

Burst RMS Current (< 1 s)

Max Peak Current During Burst

Soft Start Turn-on

Free Field

Type

Connector

Type

Connector

2

26 Hz - 18 kHz ± 6 dB
32 Hz - 16 kHz ± 4 dB
30 Hz - 16 kHz ± 4dB
± 70° 90 Hz - 17.2 kHz

3

140 dB
>100 dB (A weighted noisefloor to max SPL)

-6 dB at 70° H x 60° V

18-inch cone driver
15-inch cone driver
12-inch cone driver
2-inch throat (4-inch diaphragm) compression driver

10k impedance, electronically balanced
XLR (A-3) male and female
+4 dBu

Complementary power MOSFET output stages (audio class AB/H)

2480 watts (620 Wrms/channel x 4)
< .02 %

250V NEMA L6-20P (twistlock) inlet or IEC 309 male inlet or
Multipin VEAM option
95-125 VAC and 208-235 VAC; 50 Hz / 60 Hz
Turn on: 85 VAC; Turn off 134 VAC; 50/60 Hz
Turn on: 165 VAC; Turn off 264 VAC; 50/60 Hz
@115 V: 14 A @230 V: 7 A @100 V: 16 A
@115 V: 26 A @230 V: 13 A @100 V: 30 A
@115 V: 36 Apk @230 V: 18 Apk @100 V: 42 Apk
Inrush current < 12A @ 115V

4

Physical

Notes

Copyright © 2000 Meyer Sound Laboratories, Inc.
All Rights Reserved

Dimensions

Weight

Enclosure

Protective Grill

Rigging

1. Measurements are taken at 4 m on-axis, 1/3 octave, unless otherwise stated.

2. Response depends on loading conditions and room acoustics.

3. 1m, with pink noise or music, 1/2 space.

4. The unit is rated at 88-125V and 182-235V, 50/60 Hz, to satisfy EC standards

Height: 56.75" (1441 mm); Width: 21.26" (539 mm);
Depth: 30" (762 mm)
280 lbs (127 kg)
Multi-ply hardwood

Finish

Black textured
Perforated metal grill
Aircraft pan fittings (3 on top, 2 on bottom).
Working load for each fitting is 600 lbs, which is 1⁄5 the
cabinet breaking strength (with straight tensile pull).

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MTS-4A DIMENSIONS

All units in inches

13.00

Bottom

56.75

Top

21.26

7.5

10.63

13.16

21.97

13.36

30.26

30.00

14.125

28.5

Front

Side

REAR PANEL DETAIL

MTS-4A

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CONTACT INFORMATION

Meyer Sound Laboratories, Inc.

2832 San Pablo Avenue
Berkeley, CA 94702
tel: [phone]
fax: [phone]
e-mail: [e-mail]
www.meyersound.com

05.029.006.02 Rev A
Check www.meyersound.com for updates

14