Owner's Manual

Page 14/112 AMPLIFIER SELECTION FOR USE WITH GEO S12S
3 AMPLIFIER SELECTION FOR USE WITH GEO S12S
NEXO recommends high power amplifiers in all cases. Budget constraints are the only reason to select
lower power amplifiers. A lower power amplifier will not reduce the chances of driver damage due to
over-excursion, and may actually increase the risk of thermal damage due to sustained clipping. If an
incident occurs on an installation without protection, the fact that amplifiers only generating half their
rated output power (-3dB) are used will not change anything in respect of possible damage. This is due
to the fact that the RMS power handling of the weakest component in the system is always 6 to 10 dB
lower than the amplifier rating.
3.1 GEO S12 recommended amplification
GEO S12 is rated for very high power handling and has a 16 Ohms nominal impedance in passive
mode or 2 x 16 Ohms nominal impedance in active mode.
These high impedance values allow connection of 3 to 6 cabinets in parallel for each amplifier channel.
Nexo recommends amplifiers in agreement with table below:
Recommended
Amplifier#
Channel 1
LF in Active Mode or
LF+HF in Passive Mode
Channel 2
HF in Active Mode
GEO S12 Passive Mode
3 in parallel (5.3 Ohms load)
1750 to 3100 W / 4 Ohms
GEO S12 Active Mode
3 in parallel (5.3 Ohms load)
1750 to 3100 W / 4 Ohms 875to 1550 W / 4 Ohms
GEO S12 Passive Mode
4 in parallel (4 Ohms load)
2000 W to 3600 W / 4 Ohms -
GEO S12 Active Mode
4 in parallel (4 Ohms load)
2000 to 3600 W / 4 Ohms 1000 to 1800 W / 4 Ohms
GEO S12 Passive Mode
6 in parallel (2.7 Ohms load)
3300 to 6000 W / 2 Ohms
GEO S12 Active Mode
6 in parallel (2.7 Ohms load)
3300 to 6000 W / 2 Ohms 1650 to 3000 W / 2 Ohms
3.1.1 Current rating
It is very important that the amplifier behaves correctly under low load conditions. A speaker system is
reactive by nature: on transient signals like music it will require four to ten times more instantaneous
current than its nominal impedance would indicate. Amplifiers are generally specified by continuous
RMS power into resistive loads, however the only useful information about current capacity is the
specification into a 2 Ohm load. It is possible to perform an amplifier listening test by loading the amps
with twice the number of cabinets considered for the application (2 speakers per channel instead of one,
4 instead of 2) and running the amps up to the onset of clipping. If the signal does not noticeably
deteriorate, the amplifier is well adapted (overheating after approximately ten minutes is normal but
thermal protection must not operate too quickly after starting this test).
3.1.2 Amplifier settings
Gain value
Gain is the key to correct alignment of the system. It is especially important to know the gain of all
amplifiers used in your set-up. The tolerance should be about ±0.5 dB. In practice this can be difficult to
achieve because: