Orban Optimod-FM 8300 Operating Manual page 169

3-51
OPTIMOD-FM DIGITAL OPERATION
The single-ended noise reduction system combines a broadband downward ex-
pander with a program-dependent low-pass filter. These functions are achieved by
causing extra gain reduction in the multiband compressor. You can see the effect of
this extra gain reduction on the gain reduction meters.
Ordinarily, the gating on the AGC and multiband limiter will prevent objectionable
build-up of noise and you will want to use the single-ended noise reduction only on
unusually noisy program material. Modern commercial recordings will almost never
need it. We expect that its main use will be in talk-oriented programming, including
sports.
Please note that it is impossible to design such a system to handle all program mate-
rial without audible side effects. You will get best results if you set the MB Down
Expander control of the noise reduction system to complement the program mate-
rial you are processing. The MB Down Expander should be set higher when the in-
put is noisy and lower when the input is relatively quiet. The best way to adjust the
MB Down Expander control is to start with the control set very high. Reduce the
control setting while watching the gain reduction meters. Eventually, you will see
the gain increase in sync with the program. Go further until you begin to hear noise
modulation—a puffing or breathing sound (the input noise) in sync with the input
program material. Set the MB Down Expander control higher until you can no
longer hear the noise modulation. This is the best setting.
Obviously, the correct setting will be different for a sporting event than for classical
music. It may be wise to define several presets with different settings of the MB
Down Expander control and to recall the preset that complements the program ma-
terial of the moment.
Note also that it is virtually impossible to achieve undetectable dynamic noise reduc-
tion of program material that is extremely noisy to begin with, because the program
never masks the noise. It is probably wiser to defeat the dynamic noise reduction
with this sort of material (traffic reports from helicopters and the like) to avoid ob-
jectionable side effects. You must let your ears guide you.
Band 5 is particularly critical for noise reduction because much of the Downward Ex-
pander's utility lies in hiss reduction. Hiss has most of its energy in band 5, while
program material typically has less energy in this band, so the B5 D
E
OWN XPANDER
control's setting is critical to removing hiss while minimizing re-
D T
ELTA HRESHOLD
moval of desired program energy.
Starting in V2.1, the Downward Expander's dynamic frequency response is no longer
constrained to being strictly lowpass—Band 5 is now uncoupled from the lower
bands, so the band 5 downward expander can produce less gain reduction than
other bands. This can help prevent loss of desired high frequency material in the
program.
B3>B4 CPL ("Band 3>4 Coupling") control determines the extent to which the gains
of bands 4 (centered at 3.7 kHz) and 5 (above 6.2 kHz) are determined by and fol-
lows the gain of band 3 (centered at 1 kHz). Set towards 100% (fully coupled) this
control reduces the amount of dynamic upper midrange boost, preventing unnatu-