8-33
Processing Components - Filter
The EQ filters in the ISP-100 are full parametric. Each may be
adjusted for center frequency, boost or cut, and bandwidth.
Center Frequency
The center frequency is the frequency at which the maximum
boost or cut takes place. In the ISP-100 EQ filters the center
frequency is continuously variable from 20 Hz to 20 kHz.
Bandwidth
The bandwidth is measured at the points on either side of the
center frequency where the boost is 3 dB less than the
maximum boost or the cut is 3 dB less than the maximum cut,
whichever is appropriate. In the ISP-100 filters, bandwidth can
be expressed in either octave fraction (fractions of an octave, or
number of octaves if the bandwidth is greater than a full octave)
or quality (Q).
The conversions between octave fraction and Q are:
−
++= 14
Q
1
Q
1
log2fractionoctave 2
2
and
2
fractionoctave-
2
fractionoctave 22
1
Q
−
=
Figure 8-15
Octave Fraction vs. Q relationship.
The relationship between octave fraction and Q is shown in
Figure 8-15.
Bandwidth can be
displayed in terms
of Q or octave
fraction. See page
7-3 for information
on changing the way
filter bandwidth is
displayed.