Nexo GEO D - Manual (Page 12)

Page 12/97 GEO D G ENERAL S ET - UP I NSTRUCTIONS
2.1.4 Cabling
NEXO recommends the exclusive use of multi-conductor cables to connect the system: the cable kit is
compatible with all the cabinets, and there is no possible confusion between LF, MF and HF sections.
Cable choice consists mainly of selecting cables of the correct sectional dimension (size) in relation to
the load resistance and the cable length. Too small a cable section will increase both its serial
resistance and its capacitance; this reduces the electrical power delivered to the loudspeaker and can
also induce response (damping factor) variations.
For a serial resistance less or equal to 4% of the load impedance (damping factor = 25), the maximum
cable length is given by:
L
max
= Z x S S in mm 2 , Z in Ohm, L
max
in meters
The table below indicates these values, for 3 common sizes.
Load Impedance (Ω) 2 3 4 6 8 12 16
Cable section Maximum Length (meters)
1,5 mm² (AWG #14) 3 4.5 6 9 12 18 24
2,5 mm² (AWG #12) 5 7.5 10 15 20 30 40
4 mm² (AWG #10) 8 12 16 24 32 48 64
2.1.5 Examples:
• The GEO D10 LF section has a 16 Ohms nominal impedance, so 4x GEO D10 LF section wired
in parallel will present a 16/4 = 4 Ohm load impedance. The maximum acceptable 2x2.5 mm 2
(AWG #12) cable length L
max
for such a cluster is 10 meters.
• The GEO SUB subwoofer has a 2 x 8 Ohms nominal impedance, therefore 2 GEO SUB’s wired
in parallel will present a 2 x 4 Ohm load impedance. The maximum acceptable 2x4 mm 2 (AWG
#10) cable length L
max
is then 16 meters.
IMPORTANT
Long speaker cables induce capacitive effects – up to hundreds of pF depending on the
quality of the cable - with a low-pass effect on high frequencies. If long speaker cables
must be used, ensure that they do not remain coiled while in use.
2.2 Amplifier Selection
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.