Meyer Sound M3D - Manual (Page 11)

Meyer Sound Laboratories Inc M3D™ Line Array • 5
S
AFETY
I
SSUES
Pay close attention to these important electrical and
safety issues.
A UDIO I NPUT
The M3D or M3D-Sub presents a 10k ohm balanced input
impedance to a three-pin XLR connector with the
following connectors:
■ Pin 1 — 220k ohm to chassis and earth ground (ESD
clamped)
■ Pin 2 — Signal ( + )
■ Pin 3 — Signal ( - )
■ Case — Earth (AC) ground and chassis
Pins 2 and 3 carry the input as a differential signal; 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 with XLR connectors for balanced
signal sources. Make sure that pin 1 (shield) is always
connected on both ends of the cable. Telescoping
grounding schemes are not recommended.
Audio signals can be daisy-chained using the loop output
connector on the user panel of the M3D or M3D-Sub.
A single source can drive multiple M3Ds or M3D-Subs
with a paralleled input loop, creating an unbuffered
hard-wired loop connection.
When driving multiple M3Ds or M3D-Subs in an array,
make certain that the source device can drive the total
load impedance presented by the paralleled input circuit
of the array. The audio source must be capable of
producing a minimum of 20 dBV (10-Vrms into 600
ohms) in order to produce the maximum peak SPL over
the operating bandwidth of the loudspeaker.
!
CAUTION: Do not use a power cord adapter
to drive the M3D or M3D-Sub from a standard
three-prong Edison outlet since that connector
is rated for only 15 amps (NEMA 5-15R; 125 VAC
max.)
Figure 9. Do not use AC adapters
!
CAUTION: The M3D or M3D-Sub requires a
ground connection. Always use a grounding
outlet when connecting these units.
Figure 10. Grounded outlet and plug
WARNING: Keep all liquids away from the
M3D or M3D-Sub amplifier to avoid hazards
from electrical shock. Please refer to the
section “Using and Replacing the Rain Hood”
on page 9.
!
CAUTION: Do not operate the unit if the
power cables are frayed or broken.
chassis
ground
earth
ground
TIP: Use the rings located in the rear above
the amplifier on the M3D or M3D-Sub to
provide strain relief for the power and signal
cables.
!
CAUTION: Shorting an input connector pin to
the case can form a ground loop and cause
hum.
TIP: If abnormal noises such as hiss and
popping are produced by the loudspeaker,
disconnect the audio cable from the speaker. If
the noise stops, then most likely the problem is
not with the loudspeaker. Check the audio
cable, source, and AC power for the source of
the problem.