Dolby Laboratories DP564, User Manual

Page: 52 / 101

DP564 Multichannel Audio Decoder Listening Room Calibration
5-8
3. Keep the SPL meter in this position. Make sure that the meter is aimed at the
center speaker as you take readings for the Left, Center, and Right speakers.
4. To take the SPL readings for the Left Surround or Right Surround speakers,
keep the meter at the same angle and position as you did for the front
speakers. Turn your body 90 degrees from the Center speaker toward the wall
closest to the Surround speaker you are measuring. This minimizes
“shadowing,” or obscuring the meter with your body.
To make adjustments to an individual channel’s trim setting, use the ▲▼ buttons to
change the level setting for the current speaker. Press
Enter
to save a change in
setting, or press
Esc
to discard a change. Press
Esc
to return to the
Channel
Trims
menu.
Subwoofer Calibration
The ideal test noise for subwoofer calibration should be band-limited pink noise,
lowpass filtered at 120 Hz. The DP564 outputs band-limited pink noise (20 to 120
Hz) on the Subwoofer output. To properly calibrate the subwoofer, a real-time
analyzer (RTA) is required. If an RTA is not available, you can approximate the
settings with an SPL meter.
When using an RTA, proper calibration requires setting the LFE channel signal to be
sent to the subwoofer, within its typical bandwidth of 20–120 Hz, 10 dB higher (as
measured by the RTA) than the main channels. See Figure 5-1 for an example of an
RTA display of a properly calibrated subwoofer. The precision of this measurement
varies with the quality of the meter used.
+10 dB
SW channel
Center channel
0 dB datum
+10 dB datum
25 Hz 120 Hz 2 kHz
Figure 5-1 Real Time Analyzer (RTA) Display
If an RTA is not available, setting the subwoofer channel 4–6 dB higher, as measured
by an SPL meter, provides an approximate level. For example, set the subwoofer
channel to 89 dBC when the Center channel measures 85 dBC.