FBT QUBE SP27 - Manual (Page 36)

Shelving EQ (High Shelf shown)
InA Input A HSF:1-<::
1k00Hz Q=3.0 0.0dB
Remember – to change filter types, press BYPASS
to bypass the filter, and then use ENTER to select
the filter type.
The shelving EQ has adjustable frequency, 'Q' (or
Bandwidth) and Gain controls. These affect a range
of frequencies from the turnover freqency as shown
in the graph. For a high shelf, frequencies above
the turnover frequency will be affected. For a low
shelf, frequencies below the turnover frequency will
be affected.
Various levels of cut and boost are shown to the left,
along with various 'Q' settings (gain boosts only are
show below).
Remember that 'Q' is 1/Bandwidth, so the higher
the 'Q', the lower the Bandwidth, and the smaller the
range of frequencies affected.
Note that 'Q' settings above 0.75 will result in slight
overshoot in the filter response (as seen at the
highest setting to the right). This is normal
behaviour and does not indicate instability.
To create a flat-topped EQ filter response such as
that shown to the left, use two EQ bands, BOTH
configured as low shelves. For an overall BOOST,
set the Lower frequency filter to BOOST the desired
amount, and the Upper frequency filter to CUT by
the same amount.
This example shows one filter at 100Hz and the
other at 2kHz, with the 100Hz filter at –10dB, and
the 2kHz filter at +10dB. Varying the 'Q' affects the
slope of the response – values above 0.75 will
cause overshoot as shown.
Assymetrical responses may be achieved by
adjusting the 'Q' of each filter independantly.
Creating a Flat-topped EQ Response
34