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Audio Graphs
The audio graph (Figure 4-14) will show different displays depending
upon which EQ and Dynamics control is active. The audio graph for EQ
shows frequency response logarithmically from 20 Hz (left side) to 20 kHz
(right side). The center of the display is roughly 600 Hz. The middle
horizontal line represents 0 dB of gain and each white horizontal line
above or below it represents about 5 dB of level.
Figure 4-14 EQ Out, EQ In, and Dynamics Graphic Screens
There are four parametric equalizers to adjust the channel EQ. Each is
color-coded and their filter settings are shown in the audio graph lines with
red for the High Pass Filter (HPF) and Low EQ settings; orange for the
Low-Mid EQ; green for the High-Mid EQ, and blue for the Low Pass Filter
(LPF) and High EQ settings. When EQ is out, lines are shown across the
audio graph (left screen in Figure 4-14). When the EQ is in (active) the
audio pass band is represented in gray (middle screen in Figure 4-14).
When the Expander or Compressor controls are active the Dynamics
display is shown (right screen in Figure 4-14). It’s a very different type of
display since it graphically shows the ratio between the incoming audio
and the dynamically processed audio output. When Dynamics is out the
response line is gray. When Dynamics is in the response line is orange.
The upper half of the display reflects the Compressor settings while the
lower half reflects the Expander settings.
High Pass & Low Pass Filters
The High Pass Filter (HPF) and Low Pass Filter (LPF) can be used
independently (each can be set in or out) on any channel to narrow the
audio frequency range of that channel’s audio to less than 20 Hz – 20 kHz.
The frequency pass band is shown graphically as the controls are
adjusted: a red line represents the HPF or low frequency cutoff while a
blue line represents the LPF or high frequency cutoff.
Figure 4-15 shows the two filter screens. Adjusting the channel encoder
on the channel with the HPF screen adjusts the frequency where the lower
sounds begin to be rolled off or attenuated. The frequency range is 16 Hz
up to 500 Hz. Any audio below the selected frequency gets rolled off at 24
dB per octave. Audio above the selected frequency is not affected. The HPF
is commonly used to remove low frequency rumble and sounds emitted by
air conditioners, AC line hum, nearby traffic, footsteps, cabinet noises
being picked up by the mic arms, etc.
Adjusting the channel encoder for the channel with the LPF screen
adjusts the frequency where the higher frequency or brighter sounds begin
to be attenuated. The frequency range is from 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 noise without
affecting the voice sound—until the control is adjusted below about 5 kHz.
Audio above the selected frequency is rolled off at 24 dB per octave while
audio below that frequency is not affected.
Figure 4-15 High and Low Pass Filter Screens
The HPF and LPF can be used together to create the classic phone filter
effect by adjusting the HPF to about 300 Hz and the LPF to about 3 kHz.
Four-Band Parametric Equalization (EQ)
The four parametric EQs (EQ Lo, EQ Lo Mid, EQ Hi Mid, and EQ Hi) are
identical in operation. Each has a FREQ (frequency) control to adjust the
center-point of that parametric EQ; a BW (bandwidth) control to adjust the
width of 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 in and the
two Shelf EQs are out. The screen selection channel encoder selects
between showing the EQ Lo controls (shown in Figure 4-16) which show
both the low and low-mid EQ screens, and the EQ Hi controls, which show
both the high-mid and high EQ screens.
Figure 4-16 Parametric EQ Lo and Lo Mid Screens
Each parametric EQ’s center frequency is adjustable from 16 Hz up to 20
kHz. The bandwidth that each EQ affects is adjustable from 0.2 octaves up
to 3.00 octaves wide. Each equalizer can boost or cut the selected
frequency band +14 or -14 dB from nominal.
Typically, the parametric equalization is adjusted prior to adding any
compression or expansion since the EQ settings can interact with the
compression and expansion settings changing how they affect the audio.
Summary of Contents for EMX
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