Nexo GEO T Series CD18, User Manual

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NSTRUCTIONS
2.4.2 Operating Mode
Most two channel amplifiers available on the pro-audio market have the following operating modes:
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Stereo: two fully independent channels deliver identical power into identical loads
•
NEXO recommends Stereo Mode for HF sections when paralleling 6 GEO T series modules (2 x
6 HF per amplifier), and for CD18 amplification.
•
Bridge-Mono: the second signal channel processes the same input as the first channel, but with
reversed phase. The (single) load is connected between the two positive channel outputs using a
suitable connection. While the total output of the amplifier remains the same, the available output
voltage, the minimum impedance that can be connected and the voltage gain are doubled as
compared with stereo operation. Typically, only channel 1 input is active. Positive and negative
output connections vary depending on amplifier manufacturers.
IMPORTANT
When in Bridge-Mono mode, check your amplifier user manual for proper connection of
outputs 1(+) and (2+) in relation to input phase.
•
NEXO recommends Bridge Mono Mode for LF Rear and LF/MF Front sections when paralleling
6 GEO T series modules (1 x 6 LF rear per amplifier, 1 x 6 LF/MF front per amplifier).
•
Parallel-mono: the output terminals of the two channels are configured in parallel using an
internal relay. The (single) load is connected either to the output of channel 1 or to that of channel
2 (as if in stereo). While the total output of the amplifier remains the same the output voltage level
is also the same as in stereo mode. The minimum impedance that can be connected is reduced
by half due to the fact that current capability is doubled. Typically, only channel 1 input is active.
•
NEXO does not recommend Parallel-Mono Mode for any GEO T or CD18 amplification.
2.4.3 Advanced protection
Some high-end amplifiers may include signal processing functions similar to those found in the NX242
TDcontroller ("loudspeaker offset integration", "limiter", "compressor," etc.). Moreover, when this
processing is digital, computation latency time can introduce a few milliseconds delay from input to
output. These functions are not adapted to specific system requirements and may interfere with the
complex protection algorithms used in the NX242.
NEXO do not advise using other protection systems in conjunction with the NX242 and they should be
disabled.
IMPORTANT
For proper system protection, no latency time should be introduced between the output
of the NX242 TDcontroller and the input of loudspeakers through use of DSP modules
such as internal amplifier signal processing.
2.5 Example
For a 12 GEO T4805 and 4 CD18 cluster, and considering an amplifier model which is capable of
delivering 1 x 6000W into 4 Ohm or 2 x 3000W into 2 Ohm or 2 x 2000W into 4 Ohm, NEXO
recommends the following quantities and settings:
•
HF: 1 amplifier, 6 x GEO T4805 HF per channel, mode switch in Stereo position, Gain switch in
26 dB gain position, all dynamic or filter processing switches off.
•
LF/MF front: 2 amplifiers, 6 x GEO T4805 LF/MF per amplifier, mode switch in Bridge Mono
position, Gain switch in 26 dB gain position, all dynamic or filter processing switches off.
•
LF rear: 2 amplifiers, 6 x GEO T4805 LF Rear per amplifier, mode switch in Bridge Mono
position, Gain switch in 26 dB gain position, all dynamic or filter processing switches off.