Frequency Response; Compressor; Gain; Limiter - IMG STAGELINE DRM-880LAN Mode D'emploi

6.5.4.1 Frequency response

The diagram in the upper section of the window
indicates the frequency response of the output
channel, depending on the equalization and gain
( chapter 6.5.6) that have been set.
In the upper right of the diagram, the type of
representation can be selected: magnitude fre-
quency response ("Mag") or phase frequency
response ("Phase"). If "Mag" is selected, the field
beneath "Step dB" may be used to select the
scaling and the field beneath "Offset dB" to
select the vertical shift of the diagram. To
change a value, click the up or down arrow but-
tons next to the field.
For graphical adjustment of the filters, the
reference points (
, , , ,
[identical to the procedure for the equalization fil-
ters of the inputs ( chapter 6.4.5.1)].

6.5.5 Compressor

The compressor reduces the dynamic range and
attenuates the level above an adjustable thresh-
old. This is necessary if the dynamic range of the
audio signal is higher than allowed by the ampli-
fier system or the listening situation (e. g. in case
of background music). It is also possible to
reduce level differences (e. g. for changing
microphone distances) or to attenuate signal
peaks in order to allow a higher gain setting and
thus obtain a higher average volume.
The compressor responds to the effective
value (RMS) of the signal. The activity of the
compressor is indicated by the LED LIMITER (4)
for each output channel.
In the view of an output (e. g. "Output1", fig. 18),
under "RMS Compressor", set the parameters
for the compressor. To change a parameter,
move the corresponding slider by means of the
mouse, or (with the slider selected) use the
arrow keys or the "Pg Up" or "Pg Down" keys on
the keyboard.
1) Use the slider "Thr [dBu]" to adjust the thresh-
old value. If this threshold value is exceeded,
the gain will be reduced.
2) Use the slider "Ratio" to adjust the compres-
sion ratio. For example, a compression ratio
of 10 : 1 means that with an input level
increase of 20 dB above the threshold value,
the output level will only be increased by
2 dB.
3) Use the slider "Attack [ms]" to adjust the
attack time.
4) Use the slider "Release [sec]" to adjust the
release time, i. e. the time it takes for the gain
to reach its original value after the signal level
has fallen below the threshold value.
5) Use the slider "S / H Knee [%]" to define if the
change to the compression is to be made
abruptly (0 % = Hard Knee) or with a transi-
tion range (100 % = Soft Knee). The value
defines the size of the transition range.
6) To bypass the compressor, click the button
"Bypass". The button will appear in red. To
activate the compressor, click the button
again.
Click the button "RMS Compressor" to call up the
window "RMS Compressor & Peak Limiter ..."
(fig. 19). This window provides the same sliders
for adjusting the parameters and the button
"Bypass" for bypassing the compressor. In addi-
tion, it includes graphics that represent the signal
level of the compressor input and compressor
output, depending on the compressor adjust-
ments. Any changes to the parameters "Thresh-
old", "Ratio" or "Soft/ Hard Knee" will be instantly
reflected in the graphics.
) may be shown
⑰
View "Routing"
⑱
View of output channel "Output1"
⑲
Window "RMS Compressor & Peak Limiter"

6.5.6 Gain

In the view of an output (e. g. "Output1", fig. 18),
under "Lev [dB]", set the gain, i. e. the output
level (between -127 and +18 dB). To change the
gain, move the slider by means of the mouse, or
(with the slider selected) use the arrow keys or
the "Pg Up" or "Pg Down" keys on the keyboard.
To quickly reset the gain to 0 dB, click the button
"0 dB" beneath the slider.
To temporarily adjust the gain to 0 dB, click
the button "Bypass Level"; the button will appear
in red. To reset the gain to the value that has
been adjusted by means of the slider, click the
button again.

6.5.7 Limiter

The limiter allows the user to quickly limit the sig-
nal to an adjusted level. This prevents overloads
in subsequent units (e. g. power amplifiers) and
protects the speakers against damage. The lim-
iter operates similar to the compressor de -
scribed above. However, while the compressor
still allows an increase of the output level above
the threshold value depending on the compres-
sion rate adjusted, the threshold value of the lim-
iter defines the definite upper limit of the output
signal (compression ratio = ∞ : 1).
The limiter responds to the peak values of
the signal. The activity of the limiter is indicated
by the LED LIMITER (4).
In the view of an output (e. g. "Output1", fig. 18),
under "Peak Limiter", adjust the parameters for
the limiter. To change a parameter, move the
slider by means of the mouse, or (with the slider
selected) use the arrow keys or the "Pg Up" or
"Pg Down" keys on the keyboard.
1) Use the slider "Thr [dBu]" to adjust the thresh-
old value, i. e. maximum output level. If this
threshold value is exceeded, the gain will be
reduced.
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