Nexo GEO T - Manual (Page 10)

Page 10/67 GEO T G ENERAL S ET - UP I NSTRUCTIONS
2.1.2 CD18 connectors
The CD18 are connected to power amplifiers via NL4FC SPEAKON
connectors (not supplied). A wiring diagram is printed on the
connection panel located on the back of each cabinet. The in/out pins
of the SPEAKON sockets are identified. The sockets are connected in
parallel within the enclosures (see the Connections Diagrams section
of this manual).
2.1.3 C
a
bling
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
2.1.4 Examples:
• The GEO T4805 LF section has a 32 Ohm nominal impedance, so 6x GEO T4805 LF section
wired in parallel will present a 32/6 = 5.3 Ohm load impedance. The maximum acceptable 2x2.5
mm
2
(AWG #12) cable length L
max
for such a cluster is 13.25 meters.
• The CD18 subwoofer has a 2 x 8 Ohm nominal impedance, therefore 2 CD18s 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
NL4FC # 1- / 1+- 2- / 2+
CD18 Rear 18” VLF - 8
Ω
1(-) Negative – 1(+) Positive
Front 18” VLF - 8
Ω
2(-) Negative – 2(+) Positive
Front
Back
CD18 REAR CONNECTOR
PANEL