Meyer Sound 80 ユーザーズマニュアル

16

Most source devices are capable of 

driving loads no smaller than 10 times their 

output impedance.

Make sure that all cabling for 

looped loudspeakers is wired correctly (Pin 1 

to Pin 1, Pin 2 to Pin 2, and so forth) to prevent the 
polarity from being reversed. If one or more loud-
speakers in a system have reversed polarity, fre-
quency response and coverage will be significantly 
degraded.

Acheron loudspeakers employ Meyer Sound’s advanced 
TruPower

®

 limiting. Conventional limiters assume a constant 

loudspeaker impedance and set the limiting threshold by 
measuring voltage alone. This method is inaccurate 
because loudspeaker impedances change as frequency 
content in the source material changes, and as thermal val-
ues for the loudspeaker’s voice coil and magnet vary. Con-
sequently, conventional limiters often begin limiting 
prematurely, which reduces system headroom and dynamic 
range.

In contrast, TruPower limiting anticipates varying loud-
speaker impedances by measuring both current and voltage 
to compute the actual power dissipation in the voice coil. 
This improves performance, both before and during limiting, 
by allowing the driver to produce the maximum SPL across 
its entire frequency range. TruPower limiting also eliminates 
power compression at high levels over lengthy periods, 
which helps regulate voice coil temperatures, thereby 
extending the life of the driver.

Since TruPower limiting only reduces 

signal levels to keep voice coil temperatures 

under a safe margin, signal peaks remain unaffected.

Behavior for the Acheron Limit LEDs is described below:

■

The low- and high-frequency drivers for the Acheron 80 
and Acheron 100 are powered by separate amplifier 
channels, each with their own limiter. Limiting activity is 
indicated with a High Limit LED for the high-frequency 
channel, and a Low Limit LED for the low-frequency 
channel.

■

The two low-frequency drivers for the Acheron LF are 
powered by separate amplifier channels that are routed 
to a single limiter. When a safe power level is exceeded 
in either channel, limiting is engaged for both channels 
and the Low Limit LED lights.

When engaged, the limiters not only protect the drivers but 
also prevent signal peaks from causing excessive distortion 
in the amplifier channels, thereby preserving headroom and 
maintaining smooth frequency responses at high levels. 
When levels returns to normal, below the limiter thresholds, 
limiting ceases.

The Acheron performs within its acoustical specifications at 
normal temperatures when the Limit LEDs are unlit, or if the 
LEDs are lit for two seconds or less and then turn off for at 
least one second. If the LEDs remain lit for longer than three 
seconds, the loudspeaker enters hard limiting where:

■

Increases to the input level have no effect.

■

Distortion increases due to clipping and nonlinear driver 
operation.

■

The drivers are subjected to excessive heat and excur-
sion, which will compromise their life span and may 
eventually lead to damage over time.

The Limit LEDs indicate when a 

safe, optimum level is exceeded. If the 

Acheron 80s or Acheron 100s in a system begin to 
limit before reaching the required SPL, consider add-
ing Acheron LFs to the system (see Chapter 4, “Inte-
grating Acheron LF Loudspeakers”).

Acheron loudspeakers use optical limit-

ers that add no noise and have no effect on the 

signal when the limiters are not engaged and the 
Limit LEDs are not lit.