PRESONUS AudioBox iOne Owner's Manual page 42

5.0 Tutorials
5.3 Equalizers
Shelving EQ
Graphic EQ
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A shelving EQ attenuates or boost frequencies above or below a specified cutoff
point. Shelving equalizers come in two different varieties: high-pass and low-pass.
Low-pass shelving filters pass all frequencies below the specified
cutoff frequency while attenuating all the frequencies above it. A
high-pass filter does the opposite: passing all frequencies above the
specified cut-off frequency while attenuating everything below.
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. 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 for a particular
room. For instance, if you are mixing in a "dead" room, you may want to boost
high frequencies and roll off some of the lows. If you are mixing in a "live"
room, you might need to lower the high-midrange and highest frequencies. In
general, you should not make drastic amplitude adjustments to any particular
frequency bands. Instead, make smaller, incremental adjustments over a wider
spectrum to round out your final mix. 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 deemphasize 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.
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Owner's Manual