Orban Optimod-PC 1101, Operating Manual

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OPTIMOD-PC OPERATION
3-47
Bass Clip Threshold controls Orban’s patented embedded bass clipper. The
S
PEECH
B
ASS
C
LIP
T
HRESHOLD
control overrides the
B
ASS
C
LIP
T
HRESHOLD
control
when OPTIMOD-PC automatically detects speech (page 3-6).
The bass clipper is embedded in the multiband crossover so that harmonics created
by clipping are rolled off by part of the crossover filters. The threshold of this clipper
is ordinarily set between 0 dB and 6 dB below the threshold of the look-ahead lim-
iter, depending on the setting of the
L
ESS
-M
ORE
control in the parent preset upon
which you are basing your Advanced Control adjustments. This provides headroom
for contributions from the other four bands so that bass transients don’t smash
against the look-ahead limiter, causing audible intermodulation distortion between
the bass and higher frequency program material.
Some OPTIMOD-PC users feel that the bass clipper unnecessarily reduces bass punch
at its factory settings. To accommodate these users, the threshold of the bass clipper
is user-adjustable. The range (with reference to the look-ahead limiter threshold) is
0 to –6dB. (You can also turn the bass clipper off.) As you raise the threshold of the
clipper, you will get more bass but also more distortion and pumping. Be careful
when setting this control; do not adjust it casually. Listen to program material with
heavy bass combined with spectrally sparse midrange material (like a singer) and
listen for IM distortion induced by the bass’ pushing the midrange into the look-
ahead limiter. Although the low-IM technology in OPTIMOD-PC’s look-ahead limiter
substantially reduces this distortion, overdriving the limiter hard enough can still
cause problems.
Figure 3-4: Bass Clipper Input/Output Transfer Curves as Bass Clip Shape Control is
Varied from 0.0 (Hard) to 10.0 (Soft)