6
•
M3D
™
Line Array Meyer Sound Laboratories Inc
The input impedance for a single M3D or M3D-Sub is
10k ohms; if
n
represents the number of M3D or M3D-Sub
loudspeakers in an array, paralleling the inputs of
n
M3Ds
or M3D-Subs will produce a balanced input load of
10k ohms divided by n.
To avoid distortion from the source, make sure the
source equipment provides an adequate drive circuit
design for the total paralleled load impedance presented
by the array. Most source equipment is safe for driving
loads no smaller than ten times the source’s output
impedance.
For example, cascading an array of ten units consisting
of M3Ds and M3D-Subs produces an input impedance of
1000 ohms (10k ohms divided by 10). The source
equipment should have an output impedance of 100
ohms or less.
This is also true when connecting in parallel (loop out)
M3Ds or M3D-Subs with other self-powered Meyer
Sound loudspeakers (M3D-Subs, 650-Ps, MSL-4s, and so
on.)
An LD-1A, LD-2, or LD-3 line driver is highly
recommended when driving systems using multiple
loudspeakers, (See “Hybrid Line Arrays” on page 11.)
For details on the M3D audio input characteristics,
amplification, and protection circuitry, refer to Appendix
A, “Audio input” on page 21. For details on the M3D-Sub
Audio Input Characteristics, Amplification, and Protection
Circuitry refer to Appendix B, “Audio Input” on page 23.
AMPLIFICATION AND PROTECTION
CIRCUITRY
The M3D or M3D-Sub is powered by the Meyer Sound
HP-4 amplifier, a high-power four-channel amplifier
(1125 watts/ch. RMS) with a total power of 4500 watts.
The HP-4 amplifier utilizes complementary-power
MOSFET output stages (class AB/H). All the specific
functions for the M3D and M3D-Sub such as crossovers,
frequency, phase response, and driver protection are
determined by the control card installed inside the HP-4
amplifier.
All Meyer Sound loudspeakers are shipped with the
drivers in correct alignment. However, if a driver needs
to be replaced, make sure the replacement is reinstalled
with the correct polarity. Incorrect driver polarity impairs
the system performance and may damage the drivers.
M3D Interconnections
Each front 4 ohm, 15-inch, low-frequency driver is
powered by one channel of the HP-4/M3D amplifier.
While both rear 8 ohm, 15 inch low-frequency drivers are
connected in parallel and driven by a single amplifier
channel. The two 4-inch diaphragm high-frequency
drivers share the fourth channel of the HP-4 amplifier.
Refer to Figure 12 on page 6 to see how the drivers are
connected to the amplifier in the M3D.
Figure 11. M3D rear panel audio input connectors
audio input
loop out
Figure 12. M3D internal wiring harness diagram
(Positions are in reference to front of enclosure)
Right Front MS-415N
Left Front MS-415N
White
Green
Red
Black
-
+
-
+
MS-2001L
+
+
+
+
-
-
-
-
-
-
+
+
(Low-mid)
(Low)
Left Rear MS-815
Right Rear MS-815
Red
Black
Red
Black