Nexo GEO T - Manual (Page 45)

NEXO NX242 D IGITAL C ONTROLLER FOR GEO T Page 45/67
Please refer to the chapter in the NX242 User Manual on setting delay for proper time alignment
between GEO T Series and CD18.
5.4.6 Reversed Cardioid Pattern
Polarity checks are often performed while the system is being set up. Keep in mind that cardioid
speakers may also require a coverage test. If you invert two outputs of the NX242, you could have the
main lobe inverted and firing to the rear. It may be quite hard to detect a reversed cardioid pattern when
it involves one section of a large array.
A good practice is to test the each cabinet in the array with the front speakers only. The system is then
omni-directional. Then turn on the back speaker: you should notice a massive reduction at the back,
and additional level at the front.
This test must be done in addition to the usual polarity test.
5.4.7 Using the wrong NX242 setups for a given cabinet
Each NX242 setup is tailored for a certain NEXO loudspeaker. Using the wrong setup will create safety
and quality problems. Always check that every cabinet in your system is being driven by the correct
NX242 setup.
5.4.8 Connections
To ensure correct electronic behaviour, and to guarantee specifications and EMC performance, a
NX242 must be properly wired. Always use balanced connectors with the shield connected to pin 1 on
both sides. For more wiring recommendations please refer to the application note in the NX242 manual
update.
5.5 Delays & System alignment
5.5.1 Description
The NX242’s factory delay presets are optimised to provide the best possible crossover between the
GEO T and CD18 systems. The reference point for this adjustment is the front of each cabinet. (This
means that the internal delays needed to achieve a correct time alignment are set for cabinets standing
next to each other with both fronts aligned). We recommend that the system is adjusted so that arrivals
from GEOT array and CD18 sub-bass speakers are coincident at a fairly distant listening position.
In the examples below,
r
1
being the distance from GEO T array to listener position, and
r
2
being the
distance from CD18 to listener position, the distance difference is then
r
1
–
r
2
(specified meters or feet).
• r
1
>
r
2
, the delay should be set on the CD18 NX242 TDcontroller.
• r
1
<
r
2
, the delay should be set on the GEO T NX242 TDcontroller
• To convert the result in time delay (specified in seconds), apply:
• ∆t = ( r
1
-
r
2
)/C
r
1
and
r
2
in meters, C (sound speed)
≈ 343 m/S.
The delay parameter is set in MENU 1.2 (set the units to meters, feet or seconds according to your
preference).
5.5.2 Examples:
Flown CD18s
If the CD18s are flown behind a GEO T Array, delay will have to be adjusted on the GEO T NX242
TDcontrollers according to distance difference
r
2
–
r
1
. (see figure below).