d&b 10S - Manual (Page 8)

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.
-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 CPL circuit
d&b 10S/10S-D Manual (1.1 EN) 8