Nexo Alpha System - Manual (Page 15)

α α α
P 15
USER MANUAL
VERSION :1.01
DATE : 06/10/10
2.4. I
NITIAL
S
ET
-
UP
P
RECAUTIONS
When starting up a system including brand new cabinets, NEXO recommends gradual power ramp up. The
loudspeaker components may need stabilising during his very first hours of usage. This is particularly true
for adhesives within the speaker’s moving assemblies.
In all cases, it is advisable to connect the loudspeakers only after all the other components have been
wired and are operating correctly. This is particularly important for the amplifiers and the TDcontroller. It is
a good practice to turn down all the amplifier gains before connecting the cabinets and then turn them up
again individually with a medium level music source fed into the system. The sense LEDs of the
corresponding TDcontroller channel should light up accordingly. This will help to locate cabling errors,
particularly channel line inversions which would disable the TDcontroller protections and may invalidate the
warranty.
3. Alpha Arrays - Some Basic Rules
The concept of arraying speakers derives from two requirements :
• increased sound pressure level ;
• extended coverage area.
Array behaviour is very complex, and a bad design can lead to very poor results. The Alpha system was
designed to be flexible, allowing the user to optimise his design for a dedicated situation ; its development
included a long measurement program on a very large variety of arrays. Below are some simple rules that
the user must respect in his design.
3.1. A LPHA S2 P LACEMENT
The nominal efficiency data for Alpha S2 is given for when positioned on the floor (half-space). When flown,
the sensitivity is 3 dB lower ; on the contrary, if the Alpha S2 is positioned in an angle - respectively in a
corner -, the sensitivity will increase by 3 dB - respectively by 6 dB.
3.2. SPL V
ERSUS
F
REQUENCY
Array frequency response is strongly related to wavelength and array architecture.
• At low frequencies, wavelength being very large in relation to the size of the cabinets, speakers set
close to each other will always radiate in phase. The gain in sound pressure level L
GSPL
will be of 6 dB
per doubling, i.e. if n Alpha S2 or B1 are installed :
L
GSPL
(20Hz-100Hz) = 20 log
10
(n)
• In the mid frequency range, the gain depends on the configuration of the array, and will range from 3 to
6 dB per doubling, i.e. for n Alpha M3, M8, EM or EF :
10 log
10
(n)
≤ L
GSPL
(100Hz-1kHz)
≤ 20 log
10
(n)