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Calibrating Loudness
The user can fine-tune the amount of loudness compensation using the compensation
adjustment slider and adjusting "by ear," or by measuring SPL levels in a particular room,
then using the slider to adjust the loudness filter relative to the SPL of the room and
system gain structure.
Before calibrating loudness, set up the system gain structure (see Optimizing Audio
Levels on page88). A pre-recorded track of pink noise or pink noise from a signal
generator is preferable for this purpose. Program material can also be used (using familiar
material is recommended).
If using a signal generator, set it to output -10dBu. Tthen set the input gain of the
DSPConfigurator so the input meter reads -20dBFS. If using a recorded source, the
pink noise should be recorded at -20dBFS and the player output level setting control set
to maximum, or 0dB of attenuation. For program material, set the input level to meter at
approximately -15dBFS, with peaks safely below 0dBFS.
Unmute the mix-point from the pink noise source to the output connected to the room
amplifier being calibrated. With the basic gain structure previously set up, loudness can be
calibrated using an SPL meter or by ear. Loudness can also be set using an SPL meter,
then fine-tuned by ear.
To calibrate loudness, use a sound pressure level meter set to “C” weighting:
1. Set the Loudness processor to Bypass (Bypass button red).
2. Place the meter in an average (but somewhat prominent) listening location.
3. Generate pink noise, or start the program material playback.
4. Measure the SPL in the room.
5. In the loudness dialog, adjust the slider until the value in the SPL readout box matches
the reading on the SPL meter.
NOTE: Theoretically, calibration can be performed with the output channel volume
and post-mixer gain level set to any comfortable listening level. But a relatively
loud volume (well above the ambient noise in the room) that can be easily
measured is preferred.
Loudness is now calibrated. Disengage Bypass to hear the compensation.
Alternate method to calibrate loudness:
1. Set up the procedure using step 1 through 3 of the previous procedure.
2. Set the compensation adjustment slider to its default center position
3. Set the output channel volume fader to 0dB (100% volume),
4. Adjust the amplifier until the SPL meter reads 90dB.
Loudness is now calibrated. This method works if 90dB is an acceptable volume limit for
the room.
Setting Loudness “By Ear”
When setting loudness by ear, it is essential the system gain structure be set up first. Sit in
an average (but somewhat prominent) listening location.
1. Set the loudness processor to Bypass.
2. Set the output volume fader in the DSPConfigurator to a relatively quiet listening level.
Filter compensation from the loudness processor is most prominent at low listening
levels. Use familiar program material set to the levels described earlier.
DMP64 • Software Control 57