Orban OPTIMOD-FM 5500 Operation Manual page 147

OPTIMOD-FM DIGITAL
There are no easy choices here; you must choose the characteristic you want by
identifying your target audience and the receivers they are most likely to be using.
Regardless of which curve you use, we recommend a +2 to +5 dB boost for most
formats. Larger amounts of boost will increase the gain reduction in the lowest
band of the multiband compressor, which may have the effect of reducing some fre-
quencies. So be aware the large fixed bass boosts may have a different effect than
you expect because of the way that they interact with the multiband compressor.
Low Frequency Parametric Equalizer is a specially designed parametric equalizer
whose boost and cut curves closely emulate those of a classic Orban analog para-
metric equalizer with conventional bell-shaped curves (within 0.15 dB worst-case).
This provides warm, smooth, "analog-sounding" equalization.
LF FREQ determines the center frequency of the equalization, in Hertz.
Range is 20-500Hz.
LF GAIN determines the amount of peak boost or cut (in dB) over a 10
dB range.
LF WIDTH determines the bandwidth of the equalization, in octaves. The
range is 0.8-4.0 octaves. If you are unfamiliar with using a parametric
equalizer, 1.5 octaves is a good starting point. These curves are relatively
broad because they are designed to provide overall tonal coloration,
rather than to notch out small areas of the spectrum.
The LF parametric can be used in the mid-bass region (100-300Hz) to add "warmth"
and "mellowness" to the sound when boosting. When cutting, it can remove a
"woody" or "boxy" sound. In our presets, we tend to use it very sparingly (in the
order of 1 dB boost) to add a bit of extra bass warmth.
One formula for producing a very "big" bass sound on the air is to use a peaking
boost at 100Hz in combination with a Bass Shelf boost at 6 dB/octave.
The equalizer, like the classic Orban analog parametrics such as the 622B, has con-
stant "Q" curves. This means that the cut curves are narrower than the boost curves.
The width (in octaves) is calibrated with reference to 10 dB boost. As you decrease
the amount of EQ gain (or start to cut), the width in octaves will decrease. However,
the "Q" will stay constant.
"Q" is a mathematical parameter that relates to how fast ringing damps out. (Tech-
nically, we are referring to the "Q" of the poles of the equalizer transfer function,
which does not change as you adjust the amount of boost or cut.)
The curves in the 5500's equalizer were created by a so-called "minimax" ("minimize
the maximum error," or "equal-ripple") IIR digital approximation to the curves pro-
vided by the Orban 622B analog parametric equalizer. Therefore, unlike less sophis-
ticated digital equalizers that use the "bilinear transformation" to generate EQ
curves, the shapes of the 5500's curves are not distorted at high frequencies.
Midrange Parametric Equalizer is a parametric equalizer whose boost and cut
curves closely emulate those of an analog parametric equalizer with conventional
bell-shaped curves.
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OPERATION