In Broadcast - March 2018 - 38

38

www.inbroadcast.com | Vol: 8 - Issue 3 | March 2018

InForm

Broadcast Audio Processing Strategies
A common problem is locating the
main audio processor prior to an
overshooting studio to transmitter
link (STL); if the audio with overshoot
is applied directly to the transmitter,
you must reduce modulation (and
loudness) to remain legal. Two
common solutions are to relocate the
main audio processor after the STL,
or to fix the overshoot problem in the
STL itself. While some newer exciters
have built-in overshoot limiters, use
these only as a last resort if you can't
eliminate overshoot by other means.
Moreover, composite clipping is not
appropriate as a cure for overshooting
STLs because it adds audible nonlinear distortion and can interfere with
SCAs and the stereo pilot tone.
Receivers differ. What sounds
great on a US$3000 receiver will
not sound the same on a US$100
boom box. Act upon the broadcasting
system as a whole: from the studios
to the audience, through the lens
of the processing components-STL
transmitter-receiver.
Listen in varied environments: in
your car (or pickup truck), in the
office on table radios, with personal
"Walkman" style radios... whatever is
typical to your audience.
In addition, if your target audience
typically listens at low volume, it's
wise to do the same. It is irrelevant
to evaluate audio processing with a
pair of US$2000 loudspeakers if your
target demographic is 12 to 18 yearolds. It's prudent to have a high-quality
monitoring system as a reference,
however keep things in the context of
the target audience.

it will do and won't do for your
sound. Adjusting the AGC probably
shouldn't be your first choice to
correct a clipping or distortion
problem. Furthermore, manufacturers
implement traditional controls in
different ways - AGC drive may
not perform the same on different
products. If you are uncertain about
the description of the "Throbulator"
control, you may wish to carefully
sweep that control through its range
while monitoring its effect.
Be careful if you do so, as some
controls
can
yield
significant
changes, and make sure to return it
to its original position. If you're still
uncertain, call the manufacturer's
technical support.
Document everything before you
change anything, and document
each change along the way. At some
point, you'll need to back up to a
previous setting as in "I like the way it
sounded last Thursday." For analogue
processors, create a chart tabulating
the control parameters, and the date
of each change. If you have a digital
audio processor, save each change
to a preset. That way you can revert
to precisely the way it sounded last
Thursday.
Use an incremental approach to
adjusting the audio processing. Taking
a single huge leap is seldom (if ever)
effective. Make small changes to
perhaps only one or two parameters
per adjustment session, followed by
listening. Making large changes to
many parameters in one session is
difficult to manage: if the results aren't
satisfactory, which parameter should
be modified? What went wrong? The

Start Tweaking
Where to start? It doesn't matter
whether you're walking in "cold" or
correcting an ongoing problem.
You most likely will have a digital
processor, try one or more of the
manufacturer's recommended presets
as a starting point. Some digital
processors like the OPTIMOD have the
added advantage of a single control
that scales many parameters to
your preference, making the task of
adjustment much easier than tweaking
individual parameters, and less
time-consuming.
What to tweak. Make an effort
to understand the operation of
your audio processor(s). Study the
operating manual(s). Understand
the effect of each adjustment; what
Orban OPTIMOD 8700i

cont'd...

downside to making small adjustments
is that differences can be too subtle to
notice.
Considering your on-air presentation,
this approach is less precarious.
Listen. Allow plenty of time to
judge the effects of your changes.
Sometimes the consequences will
not be immediately evident. What
sounds fine on a few songs may sound
wretched on another. What sounds
great on your US$10,000 monitoring
system may sound wimpy on a car
radio. So, listen to many selections,
from many sources and programme
types. Listening over time will also give
your ears an opportunity to rest, and
time for you to formulate an opinion.
Where and when to stop. Ask
yourself "how will I know when I'm
done?" If the present on-air sound
is far from your goal, it's relatively
easy to judge changes to the audio
processing. However, as the processed
sound approaches the goal, subjective
differences from the ideal become
smaller, and increasingly subtle.

due to maladjustment. That same
STL problem may be the result
of simply being overdriven. If the
problem seems to originate from the
processor, the best way to determine
if it's functioning properly is to restore
all settings to the manufacturer's
recommended positions (or recall a
factory preset). You'll have a good idea
of the nature of the problem at this
point.
If the on-air sound is unsatisfactory,
but it doesn't sound broken, what
then? It will depend upon your specific
system. If the system has numerous
processors, bypass them one by one
and compare the overall sound both
ways.
Define your on-air audio goal
as much as possible. Break the
adjustment
process
down
to
manageable steps, both in the number
of system components, and in the
parameters changed in an adjustment
session. Expect to over-adjust and be
prepared to revert to some previously
documented setting.

Troubleshooting
What to do if your station's sound is
unsatisfactory.
First, determine where the problem
begins. If the programme output of
the audio console sounds fine, does
it sound okay at the output of the
processor? At the output of the STL? If
the audio sounds bad at the STL output
feeding your final audio processor,
it's unlikely that any amount of knob
twisting of the latter will compensate
for the former.
Next, determine if the problem
is due to a component failure, or

Audience First
Finally, don't get caught in a
processing war that turns into an
ego war between two engineers or
programmers. The worst thing you
can do is to forget the interests of
your audience in the heat of the
battle. Processing wars can be fun
for aggressive personalities, but the
audience is the loser. Never forget that
they have other entertainment options
including CDs, and if you deliver
obviously distorted, squashed, and
pumped audio, they may respond by
tuning out.
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