DTP CrossPoint 84 Series Matrix Switchers • Matrix Software 128
Adjusting the Post-matrix Trim
Adjusting the post-matrix trim can be challenging. This section provides guidelines, but it
may take some experimentation to set levels just right. For example, the output level can
be controlled and kept below clipping using a compressor or limiter in the output dynamics
block. However, adjusting the post-matrix trim affects how the compressor or limiter works.
1. Open the output volume dialog box and the post-matrix trim dialog box.
2. Set output volume to 100% (if the audio is too loud or distracting, mute the output).
3. With program material or pink noise present at the input, adjust the post-matrix trim until
the meter level in the output volume dialog box is below clipping (or ideally, matches the
level at the input gain meter). This maintains the audio at an optimal level in the output
signal chain, and prevents clipping at the output.
Setting the Volume Control for an External Amplifier
The maximum output of the switcher is +22 dBu. Assume that you have a power amp
with a maximum input level of +4 dBu when the input attenuator is fully open. If you want
to control volume levels using the output volume controls of the switcher and at the same
time ensure that clipping does not occur at the amplifier, you need to turn down the input
attenuator of the power amp the equivalent of 18 dB (18 + 4 = 22 dB), which puts the input
level of the amp at -14 dB (+4 minus 18 = -14). If you find that the amp setting (when the
output volume controls of the DSP Configurator are at 100%) is too loud for the room, you
can turn it down further. If the amp is not loud enough for the room, you will need a more
powerful amplifier.
On the other hand, if you wish to control volume levels using the input attenuation control
for the power amplifier, (using the same power amp max input level) you can set the output
volume control of the DSP Configurator to -18 dB. This is another way that clip points of the
two devices will be matched, ensuring that clipping will not occur.
However, Extron recommends using the output volume control of the matrix switcher for
controlling output volume. If you are using loudness processing on the unit, it works only in
conjunction with the output volume control.
Calibrating Loudness
The basic gain structure is now set up. From this point, loudness can be calibrated using an
SPL meter, a critical ear, or a combination of the two.
Setting loudness using a meter
To calibrate loudness, use a sound pressure level meter set to “C” weighting.
1. Open the post-matrix loudness processor dialog box.
2. Bypass the loudness processor.
3. Place the meter in an average listening location.
4. Start your program material playback or generate pink noise.
5. Measure the SPL in the room.
6. In the loudness dialog box, adjust the fader until the value in the “SPL” readout box
matches the reading on the SPL meter.
NOTE: Calibration can be performed with the output channel volume set to any
comfortable listening level, but a relatively loud volume that can be easily measured
is preferred.
Loudness is now calibrated.
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