Optimod-AM 9400 V1.2 Operating Manual - Orban

OPTIMOD-AM DIGITAL OPERATION 3-13
Although the controls on OPTIMOD-AM provide the flexibility you need to customize
your station's sound, proper adjustment of these controls consists of balancing the
trade-offs between loudness, density, brightness, and audible distortion. In
programming the LESS-MORE curves, we have made it easy for you to make this
trade-off. As you advance the LESS-MORE control for a given factory preset, the sound
gets louder but distortion increases. However, for each setting of the LESS-MORE
control, other processing parameters are automatically adjusted to give you the lowest
possible distortion for the amount of loudness you are getting.
There are separate LESS-MORE controls for the analog AM and digital radio
processing, making it easy to optimize each channel separately.
If you want to go beyond LESS-MORE and into the FULL MODIFY and EXPERT MODIFY
adjustments, you should carefully read and understand the following section. It
provides the information you need to adjust OPTIMOD-AM controls to suit your
format, taste, and competitive situation.
Judging Loudness
Apparent loudness in the analog AM channel will vary with the frequency response of
the radio and with the accuracy with which the radio is tuned. Narrowband radios will
usually get very much louder if tuned off center while a highly equalized signal is
being received. This means that if your auto radio is not electronically-tuned, you must
manually fine-tune its push-button settings before you can make meaningful loudness
comparisons. Loudness is a very complex psychoacoustic phenomenon. One station
cannot be judged louder than another can unless it is consistently louder on many
different receivers with many different types of program material. Because a
wideband radio reproduces more of the frequency range in which the
highly-equalized signal concentrates its energy (and to which the ear is most sensitive),
a highly equalized signal may sound quieter than an unequalized signal on a
narrowband radio, while the reverse is true on a wideband radio.
For the digital radio channel, it is much easier to compare loudness between stations
because the audio has frequency response to 15 kHz and the radios are essentially flat.
It is not wise to start a digital channel “loudness war” because setting the processor up
to cause large loudness disparities between the analog and digital channels will simply
irritate listeners and is likely to cause tune-outs as listeners are forced to constantly
grab their volume controls. Moreover, processing the digital channel for loudness is
likely to increase codec artifacts significantly.
Reverberation
In the distant past, the addition of artificial reverberation was touted as an easy
method of achieving greater loudness in AM broadcasting. Given the limitations of the
audio processing equipment of that time, this was true: reverberation increased the
signal density and average modulation without the pumping or other side effects that
heavy limiting would cause if equivalent density were to be achieved by compression
or limiting alone. However, because reverberation “smeared” the sound, it exacted a
price of decreased definition and intelligibility in many instances.
Because OPTIMOD-AM is capable of so much density augmentation without producing
audible artifacts, reverberation is neither necessary nor desirable for achieving high