EXP X-800C, Operating Instructions Manual, Page: 14 / 28

CHAPTER 3: AMPLIFICATION AND AUDIO
14
Loop Output Connector
The male XLR Loop output connector allows X-800C sub-
woofers to be looped from a single audio source. For appli-
cations that require multiple X-800Cs, connect the Loop
output of the first unit to the Input of the second, and so
forth.
NOTE: 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 X-800C is powered off.
To avoid distortion when looping multiple X-800Cs, 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
X-800C) by the number of looped loudspeakers. For exam-
ple, the load impedance for 10 X-800C 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 X-800C loudspeakers with other self-powered
Meyer Sound loudspeakers and subwoofers.
NOTE: Most source devices are capable of
driving loads no smaller than 10 times their
output impedance.
CAUTION: 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.
LIMITING
The X-800C employs Meyer Sound’s advanced TruPower
®
limiting. Conventional limiters assume a constant loud-
speaker impedance and set the limiting threshold by mea-
suring voltage alone. This method is inaccurate because
loudspeaker impedances change as frequency content in
the source material changes, and as thermal values for the
loudspeaker’s voice coil and magnet vary. Consequently,
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.
NOTE: Since TruPower limiting only reduces
signal levels to keep voice coil temperatures
under a safe margin, signal peaks remain unaffected.
Sub Limit LED
The two low-frequency drivers for the X-800C are powered
by separate amplifier channels that are routed to a single
limiter. When a safe power level is exceeded in either chan-
nel, limiting is engaged for both channels and the SUB Limit
LED lights.
When engaged, the limiter not only protects 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.
!
X-800C Limit LEDs
Active
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S UB Limit
X-800
E x c Clamp