Loudness Control - Orban OPTIMOD-PC 1101 Operating Manual

3-14
OPERATION

Loudness Control

transmission is identical to that of other properly set up Dolby Digital transmis-
sions.
If you are not driving a Dolby Digital channel, we recommend turning
the 1101's D
C
ONFIGURATION
Unlike some familiar compressors and limiters (whose gain reduction is adjusted
via threshold controls), the 1101 limiter's threshold is fixed with respect to the
input of the 1101's digital output level control so the limiter's drive level solely
determines the gain reduction. Two cascaded gain controls set this drive level.
One is MB L
D
IMIT RIVE
1101's active D
IALNORM
1101's D drop-down is set O
IALNORM
does not affect the look-ahead limiter drive.
In the transmitted Dolby Digital bitstream, setting D
value automatically turns down the home receiver's volume control, so the 1101's
output level must be turned up by the same amount to maintain a constant
loudness at the receiver. Because it is placed before the 1101's look-ahead lim-
iter, the 1101's hidden D
1101's look-ahead limiter to prevent digital clipping in the downstream transmis-
sion chain regardless of the 1101's D
user to set the correct loudness at the 1101's output solely by adjusting the
1101's active D
IALNORM
in a preset, so all TV presets automatically adapt to the 1101's current D
value.
Only the "TV" presets are set up to produce correct loudness at the con-
sumer's receiver automatically. However, you can readily adjust other
presets to produce correct loudness in Dolby Digital transmissions by ad-
justing a preset's MB D
ter peak at 0 dB on speech. Then save the result as a User Preset. The rea-
son that this works is that the 1101's D
matically scales the sensitivity of the 1101's L
the D
IALNORM
When the R
sitivity of the loudness level meter via the L
trol. This is useful for keeping the loudness level meter on-scale when us-
ing radio-style presets, which are generally louder than the "TV" presets.
This allows you to compare the loudness of radio-style presets.
OPTIMOD-PC's third-generation CBS Loudness Controller and BS.1770 Safety Limiter
cooperatively and automatically control subjective loudness. The BS.1770 Safety Lim-
iter follows the CBS Loudness Controller in the signal path.
Useful in sound-for-picture applications, particularly when government regulations
like the CALM Act require control of subjective loudness, the 1101's third-generation
CBS Loudness Controller follows the multiband compressor in the 1101's signal flow
diagram. However, it takes into account the effect of the following look-ahead lim-
R S
IALNORM EFERENCE OURCE
tab in the 1101's I/O M
; the second is a "hidden" control whose gain is set by the
value. This second gain control is only active when the
; otherwise, the control is set to 0 dB so it
FF
gain control achieves this while allowing the
IALNORM
IALNORM
value—it is unnecessary to adjust any other controls with-
control to make the 1101's L
RIVE
R S selector is not O
EFERENCE OURCE
S selector is O
EFERENCE OURCE
.
to O This control is located in the
FF
.
IXER
to a less negative
IALNORM
setting. This arrangement allows the
OUDNESS
R control auto-
IALNORM EFERENCE
L
OUDNESS EVEL
.
FF
, you can manually scale the sen-
FF
M S
OUDNESS ETER ENSITIVITY
ORBAN MODEL 1101
IALNORM
L me-
EVEL
meter when
con-