Dolby Laboratories DP564 - Manual (Page 51)

DP564 Multichannel Audio Decoder Listening Room Calibration
5-7
Measuring SPL
Before generating test noise, press
Ref
to check that the master volume level is set to
0 dB. Master volume should remain at 0 dB while you set channel trim levels. The
Ref
button remains lit as long as the master volume level is set to 0 dB. If the
Ref
light
turns off, press
Ref
again to return the level to 0 dB. If the overall level needs
adjustment when you begin measuring SPL, adjust the
Master Trim
level before
adjusting the levels for individual channels.
WARNING: Before you turn on a test noise, be sure that your playback system is set to
a moderate listening level. Adjust your amplifiers, self-powered speakers, or mixer, not
the DP564 master volume. An overall attenuation of up to –20 dB can be applied using
the DP564 master trim control. Beware that if the playback level is very high, you may
risk damaging your speakers or possibly your hearing. The default test noise level from
the DP564 is –20 dBFS to the digital outputs (+4 dBu to the analog monitor outputs).
To generate test noise to the analog outputs:
1. From the
Monitor Config
menu, select
Channel Trims
, press
Enter
,
then press
Enter
again to see the
Test Noise
menu
2. Use the ▲▼ buttons to select either
Wideband
(if your listening system has
full-range speakers at all channel outputs) or
Filtered
(if any of your
speaker settings is
Small
), then press
Enter
.
The test noise cycles around the speakers in this order: Left, Center, Right, Right
Surround, Back Surround Right, Back Surround Left, Left Surround, and Subwoofer
channels—remaining two seconds at each output before moving on to the next.
When you enter an individual channel trim adjustment menu, the test noise remains at
that channel until you complete the adjustment and move to another channel, which
allows you to adjust the SPL for each channel carefully, using the following
procedure.
To accurately measure SPL:
1. Sit in the reference listening position. Set the SPL meter to “C” weighting and
“slow” response.
2. Facing the front speakers, hold the SPL meter at chest level, with the
microphone facing up at an angle of approximately 45 degrees to the center
speaker. Keep the meter at arm’s length to prevent measuring audio that may
reflect from your body.