d&b 4S - Manual (Page 7)

2.3.1. Controller settings
For acoustic adjustment the functions CUT, HFA and CPL can be
selected.
CUT circuit
Set to CUT, the cabinet low frequency level is reduced. The
cabinets are now configured for use with d&b active subwoofers.
HFA circuit
In HFA mode (High Frequency Attenuation), the HF response of the
system is rolled off. HFA provides a natural, balanced frequency
response when a unit 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 circuit
The CPL (Coupling) circuit compensates for coupling effects
between the cabinets when building closely coupled arrays. CPL
begins gradually around 1 kHz, with the maximum attenuation
below 200 Hz. To achieve a balanced frequency response, the
CPL circuit can be set to dB attenuation values between 0 and –9.
Positive CPL values create an adjustable low frequency boost (0 to
+5 dB) and can be set when the system is used in full range mode
without subwoofers.
2.4. Dispersion characteristics
The following graphs show dispersion angle over frequency of a
single cabinet plotted using lines of equal sound pressure (isobars)
at –6 dB and –12 dB.
Fig. 8: Isobar diagram horizontal
4S
Fig. 9: Isobar diagram vertical
-5
0
5
10
-10
-15
-20
-25
-30
20 100 1k 10k 20k
Fig. 6: Frequency response correction of HFA circuit
Fig. 7: Frequency response correction of the CPL circuit
d&b 4S/5S Manual (1.2 EN) 7