PreSonus StudioLive 24.4.2 - Manual (Page 74)

70
5 Digital Effects | Master Control
5.2 Scenes
StudioLive™ 24.4.2/16.4.2
Owner’s Manual
5.3 Graphic Equalizers
The StudioLive features 4 stereo, 31-band, graphic EQs. A graphic EQ is a multiband
equalizer that uses sliders to adjust the amplitude for each frequency band. It
gets its name from the positions of the sliders, which graphically display the
resulting frequency-response curve. While the GEQ menu is active, the encoders
in the Fat Channel are used to make amplitude adjustments, and the meter
LEDs display the “slider” positions. The center frequency and bandwidth are
fixed; the level (amplitude) for each band is the only adjustable parameter.
Graphic EQs are generally used to fine-tune the overall mix to create the aesthetic
that you are trying to achieve. For example, if you are mixing a rock band, you
may want to boost some of the low end to get more pummeling kick and
toms. In general, you do not want to make drastic amplitude adjustments to
any particular frequency band. Making smaller, incremental adjustments over
a wider spectrum will round out your final mix for a more polished sound.
To assist you with these adjustments, here is an overview of
which frequencies affect different sound characteristics:
Sub-Bass (16 Hz to 60 Hz). The lowest of these bass frequencies are felt, rather
than heard, as with freeway rumbling or an earthquake. These frequencies give
your mix a sense of power, even when they only occur occasionally. However,
overemphasizing frequencies in this range will result in a muddy mix.
Bass (60 Hz to 250 Hz). Because this range contains the fundamental notes
of the rhythm section, any EQ changes will affect the balance of your mix,
making it fat or thin. Too much emphasis will make for a boomy mix.
Low Mids (250 Hz to 2 kHz). In general, you will want to emphasize the lower
portion of this range and de-emphasize the upper portion. Boosting the range
from 250 Hz to 500 Hz will accent ambience in the studio and will add clarity to
bass and lower frequency instruments. The range between 500 Hz and 2 kHz
can make midrange instruments (guitar, snare, saxophone, etc.) “honky,” and too
much boost between 1 kHz and 2 kHz can make your mix sound thin or “tinny.”
High Mids (2 kHz to 4 kHz). The attack portion of percussive
and rhythm instruments occurs in this range. High mids are also
responsible for the projection of midrange instruments.
Presence (4 kHz to 6 kHz). This frequency range is partly responsible for the clarity of
a mix and provides a measure of control over the perception of distance. If you boost
this frequency range, the mix will be perceived as closer to the listener. Attenuating
around 5 kHz will make the mix sound further away but also more transparent.
Brilliance (6 kHz to 16 kHz). While this range controls the
brilliance and clarity of your mix, boosting it too much can cause
some clipping so keep an eye on your main meter.
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 set by the user via 31 front-panel sliders. A well-designed
graphic EQ creates an output frequency response 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 if, it varies with the gain and how the filters are summed
or cascaded. In general, narrower bandwidth signifies a more precise 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