55
hum, nearby traffic, footsteps, cabinet noises being picked up by the mic
arms, etc.
Adjusting the channel encoder on the channel with the LPF display
adjusts where the higher frequency or brighter sounds are attenuated. The
control range is 20 kHz down to 1 kHz. This control can selectively remove
higher frequency sounds like hiss from an air conditioner, chair squeaks,
and other high frequency noises without affecting the voice sound
—
unless
the control is adjusted below about 5 kHz. Audio above the selected
frequency gets rolled off at 24 dB per octave while audio below that
frequency is not affected.
The HPF and LPF can also be used together to create the classic phone
filter effect on a voice. To do this, adjust the HPF to about 300 Hz and the
LPF to about 3 kHz. If this setting is saved as an EQ file, it can be loaded
into any channel using the DMX Surface Setup
app’s EQ controls
.
Four-Band Parametric Equalization
The four parametric EQs (EQ Lo, EQ Lo Mid, EQ Hi Mid, and EQ Hi) are
all identical in operation and actually have the same set of parameters and
control ranges.
The three EQ Lo screens are shown in Figure 4-12. Note their red color
which matches the color shown in the EQ Graphic screen. Each parametric
EQ has a FREQ (frequency) control to adjust the center-point of that EQ; a
BW (bandwidth) control to adjust the width of frequencies being affected
by that EQ; and a LEVEL control to set the amount of boost or cut applied
to that equalizer.
These controls are active when EQ is set In and the two Shelf EQs are
set Out. The channel 8 or 16 encoder is used to select between showing
EQ Lo (which shows EQ Lo and EQ Lo Mid controls) and EQ Hi (which
shows the EQ Hi Mid and the EQ Hi controls).
Figure 4-12 Parametric EQ Lo and Lo Mid Screens
Each parametric EQ
’s center frequency
is adjustable from 16.1 Hz up to
20.2 kHz. The bandwidth that each EQ affects is adjustable from 0.20
octaves wide up to 3.00 octaves wide. Each equalizer can boost or cut the
selected frequency band +14 or -14 dB from unity gain in 0.1 dB steps.
Typically, the parametric equalization is adjusted prior to adding any
compression or expansion since the EQ settings and the compression and
expansion settings interact with one another’s operation
.
EQ Lo Shelf & EQ Hi Shelf
These two filters are only active when EQ is set In along with either or
bot
h Shelf’s
being set In. When active, the screens for the EQ Lo and/or
EQ Hi are affected. While the Shelf is active it assigns a fixed bandwidth so
the BW (Bandwidth) screen is not shown. The FREQ and LEVEL controls
operate the same as for the regular parametric equalizer.
The two Lo Shelf controls are used to boost or cut the low frequencies
below the selected frequency by the amount set by the level control.
The two Hi Shelf controls are used to boost or cut the high frequencies
above the selected frequency by the amount set by the level control.
The channel encoder with the EQ Shelf LEVEL screen sets the amount of
boost (up to +14 dB) or cut (up to -
14 dB) that’s applied. The channel
encoder with the EQ Shelf FREQ screen sets where that shelf ends or
begins. The Lo Shelf FREQ control adjusts where the low shelf ends, from
20.3 Hz up to 198 Hz. The Hi Shelf FREQ control adjusts where the high
shelf starts, which can be from 4 kHz up to 20.2 kHz.
Dynamics
–
Compression and Expansion
When
Dynamics
is set In the Compressor and Expander functions are
activated. The Compressor has five controls, with an orange background,
which affect the overall dynamic range of the audio signal by controlling
the loudest audio levels. The six Expander controls (teal background),
work at the opposite end of the dynamic range, controlling what happens
with very low-level audio signals.
Figure 4-13 Compressor Screens
Compression
A Compressor controls the overall loudness of an audio signal. A small
amount of compression is often applied to mics and phone callers to
“
even
out
”
their overall audio levels. Applying higher levels of compression, along
with using a higher threshold, allows one to obtain consistent maximum
loudness for “shock jocks”
and
“in
-your-
face” commenta
tors.
The compressor in the DMX is a soft knee compressor which means its
operation is less noticeable
—
for most settings. Setting the controls to their
extreme settings, to get that
“
loud and in your face
”
sound that
’
s right on
the edge of audio distortion, can cause audible compression artifacts.