d&b 24C - Manual (Page 10)

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 actively driven d&b
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 different acoustic
properties of the venue. CPL begins gradually around 1 kHz, with
the maximum attenuation below 250 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.
-5
0
5
10
-10
-15
-20
-25
-30
20 100 1k 10k 20k
Frequency response correction of HFA circuit
Frequency response correction of CPL circuit
d&b 24C/24C-E Manual 1.3 en 10