Klark Teknik DN370, Руководство оператора

Страница: 25 / 30

DN Operators Manual - 370 Page 19
DN370 applications
The notch filters on the DN370 can be used to eliminate a common
problem with graphic equalisers - the control of frequencies that lie
between the ISO standard frequency centres. In the adjacent example
to cut 900 Hz, a single notch filter can be used to produce a steep notch
in the frequency response without affecting adjacent frequencies (a). In
contrast with a Symmetrical-Q equaliser, the only solution available is
to cut both the 800 Hz and 1 kHz faders, and whilst there is nearly 16 dB
of attenuation at 900 Hz, a very broad range of frequencies are also
affected, particularly when a Symmetrical-Q equaliser with a wide
response is used (c). A narrow Symmetrical-Q response affects a less
broad range of frequencies, although at the expense of less attenuation
at the desired frequency (b).
The proportional-Q response of the DN370 simultaneously allows
gentle contouring of the frequency spectrum and precise control of
specific problem frequencies. The sweepable notch filters further
enhance this capability. The blue trace shows a high shelf filter created
using the faders from 2.5 kHz upwards, and a notch created by fully
cutting the 800 Hz fader (Channel A on the front panel view). The red
trace shows the same shelf filter response, but using a notch filter to cut
800 Hz, showing the greater precision offered by the notch filters
(Channel B on the front panel view).
In contrast, the limitation of Symmetrical-Q equalisers can be seen
in the adjacent traces - a wide response (a) gives a smooth shelf
filter but affects a very broad range of frequencies when
attempting to use it as a notch filter, whilst a narrow response (b)
gives a much sharper notch, but at the expense of excessive ripple
in the shelf filter. Even with a narrow response, the Symmetrical-Q
equaliser affects a broader range of frequencies than using the
Proportional-Q response of the DN370’s faders.
The ability to overlap the notch filters, both with each other and with the
graphic EQ bands, allows very deep notches to be created. The adjacent
trace shows the responses of a single notch filter, two overlapped notch
filters (a) and two notch filters overlapped with an EQ band (b), each
resulting in greater attenuation (c). Nearly 45 dB of attenuation is
possible when using the notch filters in conjunction with the EQ bands.
A typical application of DN370 would be to EQ a monitor wedge, the red
trace shows how both the high and low pass filters have been used to
shape the overall response, and the use of the two notch filters to
attenuate particular problem frequencies. Note that the faders are
completely flat, and so can be used to make incremental changes
relative to the response shown above. In contrast, a Symmetrical-Q
equaliser even with a high pass filter cannot produce the same
response, either with a wide or narrow response (b and a traces). The
effect of the interaction caused by combining the individual fader
responses makes it impossible to match the response created using the
DN370’s filters, and whilst the narrow response is more able to produce
the desired notches, it is again at the expense of ripple in the low pass
filter response.
A Symmetrical-Q equaliser lacking the additional filters cannot produce
a high pass filter response using just its faders, either with a wide or
narrow response (b and a traces). The user may assume that subsonic
frequencies are being attenuated by cutting the bottom faders but the
graph shows that this is not the case.
-14
+2
-12
-10
-8
-6
-4
-2
+0
d
B
u
200 20k 500 1k 2k 5k 10k Hz
d
B
u
-15
+15
-10
-5
+0
+5
+10
300 4k 400 500 600 700 800 900 1k 2k 3k Hz
a
b
c
a
b
a
b
c
10 20k 20 50 100 200 500 1k 2k 5k 10k Hz
-40
+0
-35
-30
-25
-20
-15
-10
-5
d
B
u
a
b
Hz
-40
+0
-35
-30
-25
-20
-15
-10
-5
d
B
u
10 20k 20 50 100 200 500 1k 2k 5k 10k
a
b