2.3.1 Controller settings
Depending on the loudspeaker setup selected, the CUT, HFA, CPL
and HFC functions are available for acoustic adjustment.
CUT mode
Set to CUT, a high pass filter with a 95 Hz cut off frequency is
inserted in the controller signal path. The AL60/AL90 are now
configured for use with actively driven d&b V-SUB or V-GSUB
subwoofers.
HFA mode (PS setup only)
In HFA mode (High Frequency Attenuation), the HF response of the
system is rolled off. HFA provides a natural, balanced frequency
response when a cabinet is placed close to listeners in near field or
delay use.
High Frequency Attenuation begins gradually at 1 kHz, dropping
by approximately 3 dB at 10 kHz. This roll off mimics the decline
in frequency response experienced when listening to a system from
a distance in a typically reverberant room or auditorium.
CPL function
The CPL (Coupling) function compensates for coupling effects
between the cabinet and close boundary surfaces. CPL begins
gradually around 1 kHz, with the maximum attenuation below
400 Hz. To achieve a balanced frequency response, the CPL
function can be set to dB attenuation values between 0 and –9.
Positive CPL values create an adjustable low frequency boost (0 to
+5 dB) at around 65 Hz and can be set when the system is used in
full range mode without subwoofers.
HFC function
Selecting the HFC (High Frequency Compensation) function
compensates for loss of high frequency energy due to absorption
in air when loudspeakers are used to cover far field listening
positions.
The HFC function has two settings (HFC1, HFC2) for different
distances the cabinets need to cover. The settings should be used
selectively; HFC1 for cabinets covering distances larger than 15 m
(49 ft) and HFC2 for those covering distances larger than 25 m
(82 ft).
The compensation is adjusted for a typical relative humidity of
40 %. With lower humidity the absorption by air increases
therefore the distances where the respective HFC setting provides a
correct equalization are shorter than indicated above.
Using the HFC function provides the correct sound balance
between close and remote audience areas, whilst all amplifiers
driving the array can be fed with the same signal.
-5
0
5
10
-10
-15
-20
-25
-30
20
100
1k
10k
20k
Frequency response correction in HFA mode*
*schematic diagram
Frequency response correction of the CPL function*
*schematic diagram
Frequency response correction of the HFC function*
*schematic diagram
d&b AL60/AL90 Manual 1.2 en
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