Graphic Equalizer - PRESONUS StudioLive 16.0.2 Owner's Manual

5 Scenes, Presets, System Menu, and MIDI Control
5.3

Graphic Equalizer

Graphic Equalizer
5.3
EQ-O-Matic
44 44
The StudioLive 16.0.2 features a 31-band, 1/3-octave graphic
EQ that can be inserted on the Main output bus.
If this were a analog graphic equalizer, it would look like this:
The StudioLive graphic EQ features an innovative design that sets it apart
from traditional graphic EQs. Traditionally, a 31-band graphic EQ uses 31
second-order shelving filters with fixed frequencies in order to simulate
a curve that you set with the 31 front-panel sliders. A well-designed
graphic EQ creates an output frequency responses that corresponds as
closely as possible to the curve displayed graphically by the sliders.
In an analog EQ, this is achieved by carefully choosing the bandwidth of the filter
and deciding how, or whether, it varies with the gain and how the filters are summed
or cascaded. In general, narrower bandwidth signifies a higher-quality EQ. But
in traditional graphic EQ designs, the center frequency of each band is fixed.
PreSonus took a different approach with the StudioLive. The StudioLive graphic
EQ is a pool of shelving filters from which coefficients like cutoff frequency,
bandwidth, and gain are extracted through a process of curve-fitting. The curve
entered by the user is first oversampled. The system then works with an internal
curve made up of 128 bands to find coefficients for the first shelving filter
that, when subtracted from the user's curve, will produce the flattest possible
response: 0 dB. The resulting response is then used to find coefficients for the
second shelving filter through the same optimization process. Coefficients
for all available shelving filters are found through a recursive process.
Unlike conventional designs, the frequency and bandwidth of the "bands"
depends on the curve entered by the user. This allows for much tighter matching
of that curve. Because of this innovative design, the accuracy of the StudioLive
EQ might feel "wrong" at first. The curve-fitting process is capable of very steep
transitions, and unlike conventional analog graphic EQs, what you see is what
you get. With a carefully drawn, smooth curve the StudioLive EQ will have almost
no frequency ripple. The StudioLive EQ is also capable of very sharp notches.
To widen a notch or a bump on a particular band, just bring the adjacent
bands closer to that band's gain, and the bandwidth will change accordingly.
Making drastic adjustments too quickly may create an audio artifact as the
new curve is redrawn and crosses over an audio peak. If you are hearing audio
artifacts while setting up the graphic EQ, try creating a smoother curve.
To turn on and make changes to the graphic EQ, press the GEQ Encoder Mode
button. The GEQ menu will open in the LCD. When the GEQ page is active, the meters
and encoders of the Fat Channel become the controls for the graphic EQ.
As you touch a knob, you will notice that its band number, frequency, and gain
are displayed in the GEQ menu. The 31 bands range from 20 Hz to 20 kHz. The
PreSonus StudioLive 16.0.2
™