Extron electronic DMP 64 manual Calibrating Loudness, Setting Loudness “By Ear”

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 page 88). 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 -10 dBu. Tthen set the input gain of the DSP Configurator so the input meter reads -20 dBFS. If using a recorded source, the pink noise should be recorded at -20 dBFS and the player output level setting control set to maximum, or 0 dB of attenuation. For program material, set the input level to meter at approximately -15 dBFS, with peaks safely below 0 dBFS.

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 0 dB (100% volume),

4.Adjust the amplifier until the SPL meter reads 90 dB.

Loudness is now calibrated. This method works if 90 dB 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 DSP Configurator 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.

DMP 64 • Software Control 57