Meyer Sound M'elodie, Operating Instructions Manual

11

CHAPTER 3

More than just a self-powered loudspeaker, M’elodie uses 
sophisticated amplification and protection circuitry and 
an advanced limiting system to produce consistent and 
predictable results in any system design. This chapter will 
help you understand and harness the power of the M’elodie 
loudspeaker’s amplifier and audio systems.

AUDIO INPUT

The M’elodie loudspeaker presents a 10 kOhm balanced 
input impedance to a three-pin XLR connector with the fol-
lowing connections:

■ 

Pin 1 — 220 kOhm to chassis and earth ground (ESD 
and RF clamped)

■ 

Pin 2 — Signal ( + )

■ 

Pin 3 — Signal ( - )

■ 

Case — Earth (AC) ground and chassis

CAUTION: 

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; pin 2 is 
hot relative to pin 3, resulting in a positive pressure wave 
when a positive signal is applied to pin 2. Pin 1 is con-
nected to earth through a 220 kOhm, 1000 pF, 15 V clamp 
network. 

This ingenious circuit provides virtual ground lift at audio 
frequencies, while allowing unwanted signals to bleed to 
ground. 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.

CAUTION: 

Ensure that all cabling carrying 

signal to M’elodie loudspeakers in an array 

is wired correctly: Pin 1 to Pin 1, Pin 2 to Pin 2, and 
so forth, to prevent the polarity from being reversed. 
Any number of M’elodie loudspeakers (even one) in 
the array with reversed polarity will result in severe 
degradation in frequency response and coverage.

TIP: 

 If abnormal noises such as hissing and 

popping are produced by the loudspeaker, 

disconnect the audio cable from the loudspeaker. If 
the noise stops, most likely the problem is not with 
the loudspeaker. Check the audio cable, source, and 
AC power to pinpoint the problem.

Audio signals can be daisy-chained using the loop output 
connector on the user panel of the M’elodie loudspeaker 
(Figure 3.1). A single source can drive multiple M’elodie 
loudspeakers with a paralleled input loop, creating an un-
buffered hard-wired loop connection.

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Firmware

Looping Audio Input
10k

Ω

 Balanced

Input

Loop

AC LOOP OUTPUT

115/230V

~

   50-60 Hz

10A RMS @115V

~

12.5A RMS @230V

~

Class 1 Wiring

!

AC INPUT RATING

115/230V

~

   50-60 Hz

5A RMS @115V

~

2.5A RMS @230V

~

1500W BURST MAX

Figure 3.1. 

Rear panel audio input connectors 

When driving multiple M’elodie loudspeakers 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 source device must be capable of producing  
20 dBV (10 volts rms into 600 ohms) in order to produce the 
maximum peak SPL over the operating bandwidth of the 
loudspeaker.

To avoid distortion, make sure the source device provides 
an adequate drive circuit design for the total paralleled load 
impedance presented by the array. The input impedance for 
a single M’elodie loudspeaker is 10 kOhms. To calculate the 
load impedance of the array, divide 10 kOhms by the num-
ber of paralleled loudspeakers in the array. If 

n

 represents 

the number of M’elodie loudspeakers in an array, paralleling 
the inputs of 

n

 M’elodie loudspeakers will produce a bal-

anced input load of 10 kOhms divided by 

n

.

NOTE:

Most source devices are safe for 

driving loads no smaller than 10 times the 

source’s output impedance.

For example, cascading an array of 10 M’elodie loudspeak-
ers produces an input impedance of 1,000 ohms, or 10 
kOhms divided by 10. The source device should have an 
output impedance of 100 ohms or less. This is also true 
when connecting M’elodie loudspeakers in parallel (loop 
out) with other self-powered Meyer Sound loudspeakers 
(e.g., MICA, 700-HP, 600-HP, or 650-P). 

NOTE:

Meyer Sound’s Galileo™ loudspeaker 

management system and LD-3 compensat-

ing line driver are highly recommended when driving 
systems using multiple loudspeakers. These proces-
sors, in addition to maintaining signal integrity for 
long cable paths, offer independent outputs and 
filters to help you integrate sub-systems and optimize 
M’elodie array performance. 

CHAPTER 3: AMPLIFICATION AND AUDIO