Klark Teknik HELIX SYSTEM DN9344 Operator's Manual page 57

Proportional Q
Klark Teknik
+12
+10
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+0
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Proportional Q is the mode of operation familiar to users of the Klark Teknik analogue graphic equalisers such
as the DN360. As the amount of cut or boost is increased, the Q also increases. This has the effect of making
the equaliser "focus" more tightly as the amount of EQ is increased. This allows a fairly low-Q filter at small
cut and boost settings, providing gentle control of tonal balance and low ripple. At high gain settings, a
proportional-Q equaliser "automatically" increases Q for more dramatic problem solving such as suppression
of feedback or unwanted resonances. In the interests of clarity, the Q setting shown on the display is the Q at
full cut or boost - the Q at lower gain settings will be lower than that shown on the panel.
Constant Q
Klark Teknik
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+10
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A constant Q equaliser has the same Q at all cut and boost settings. In other words, the bandwidth between the
3dB points does not change at all as the gain is adjusted.The really important thing to notice about this is that
the resulting frequency response is NOT symmetrical in cut and boost. This is because of the definition of Q
which is based on the 3dB points
course, 0dB, and the bandwidth is determined by the -3dB points
minimum gain (at the centre frequency). This makes a lot of sense musically too - if you listen to a music
signal and apply a notch filter, and then change the shape of the curve around the minimum gain (centre) point,
it will make little difference to the sound (since that area is already attenuated a lot). However, if you change
the curve around the 3dB points, this will affect the sound much more, as more or less of the signal "falls into"
the notch. It is this bandwidth that the constant-Q filter is keeping constant. Note that many equalisers that are
described as "Constant Q" by their manufacturers do NOT fall into this category, and are what we would term
symmetrical-Q designs.
Proportional Q
50 100 200
Constant Q
50 100 200
relative to maximum gain.
500 1k 2k
Hz
500 1k 2k
Hz
The maximum gain of the filter when in cut is, of
relative to 0dB
49
abc
l
06/17/02 12:38:05
5k 10k 20k
06/19/02 10:41:39
5k 10k 20k
and NOT relative to the