Meyer Sound 100 ユーザーズマニュアル

15

The Acheron drivers are powered by a two-channel propri-
etary Meyer Sound amplifier with MOSFET output stages. The 
audio signal is processed with an electronic crossover, cor-
rection filters for phase and frequency response, and driver 
protection circuitry. Each channel has peak and rms limiters 
that prevent driver over-excursion and regulate the tempera-
ture of the voice coil.

The Acheron rear panel has an audio Input and Loop output 
connector, Limit LEDs, and an optional RMS module for 
connecting to the RMS remote monitoring system (see 
Chapter 6, “The RMS Remote Monitoring System”).

The Acheron and Acheron LF include female XLR Input and 
male XLR Loop output connectors.

The female XLR Input connector accepts a balanced audio 
signal with an input impedance of 10 kOhm. The connector 
uses the following wiring:

■

Pin 1 — 220 kOhm 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 1 is 
connected to earth through a 220 kOhm, 1000 pF, 15 V 
clamped network. This circuitry provides virtual ground lift 
for audio frequencies while allowing unwanted signals to 
bleed to ground. Make sure to use standard, balanced XLR 
audio cables with all three pins connected on both ends. 
Telescopic grounding is not recommended, and shorting an 
input connector pin to the case may cause a ground loop, 
resulting in hum.

If unwanted noise or hiss is produced by 

the loudspeaker, disconnect its input cable. If 

the noise stops, there is most likely nothing wrong 
with the loudspeaker. To locate the source of the 
noise, check the audio cable, source audio, and AC 
power.

The male XLR Loop output connector allows Acheron and 
Acheron LF loudspeakers to be looped from a single audio 
source. For applications that require multiple Acherons and 
Acheron LFs, connect the Loop output of the first unit to the 
Input of the second, and so forth. 

The order in which loudspeakers are 

connected when looping audio signals is unim-

portant. The Loop connector is wired in parallel to the 
Input connector and transmits the unbuffered source 
signal even when the Acheron is powered off.

To avoid distortion when looping multiple Acherons, make 
sure the source device can drive the total load impedance of 
the looped loudspeakers. In addition, the source device 
must be capable of delivering approximately 20 dBV 
(10 V rms into 600 ohms) to yield the maximum peak SPL 
over the entire operating bandwidth of the loudspeakers. 
Most professional audio equipment can transmit these 
source levels.

To calculate the load impedance for the looped loudspeak-
ers, divide 10 kOhms (the input impedance for a single 
Acheron) by the number of looped loudspeakers. For exam-
ple, the load impedance for 10 Acheron loudspeakers is 
1000 ohms (10 kOhms / 10). To drive this number of looped 
loudspeakers, the source device should have an output 
impedance of 100 ohms or less. This same rule applies 
when looping Acheron loudspeakers with other self-pow-
ered Meyer Sound loudspeakers and subwoofers.