OPTIMOD SURROUND PROCESSOR OPERATION
3-5
getting the audio to sound bright and the trade-off is only between
loudness and distortion.
Perhaps the most difficult part of adjusting a processor is determining the best
trade-off for a given situation. We feel that it is usually wiser to give up ultimate
loudness to achieve low distortion. A listener can compensate for loudness by simply
adjusting the volume control. However, a listener cannot make an excessively com-
pressed or peak-limited signal sound clean again.
If processing for high quality is done carefully, the sound will also be excellent on
small receivers. Although such a signal might fall slightly short of ultimate loudness,
it will tend to compensate with an openness, depth, and punch (even on small
speakers) that cannot be obtained when the signal is excessively squashed.
If women form a significant portion of the station’s audience, bear in mind that
women are more sensitive to distortion and listening fatigue than men are. In any
format requiring long-term listening to achieve market share, great care should be
taken not to alienate women by excessive stridency, harshness, or distortion.
Processing for Low Bit Rate Codecs
8685’s Five-Band processing includes PreCode™ technology to minimize codec arti-
facts. To exploit PreCode technology fully ( minimizing “phasey” and “underwater”
artifacts in low bit rate codecs), do not set up OPTIMOD 8685 for very bright sound
(with large amounts of high frequency energy) because this is likely to exacerbate
artifacts. Some appropriate presets include J
AZZ, SMOOTH JAZZ, GOLD, ROCK SOFT, and
the C
LASSICAL presets. Avoid presets like CRISP and EDGE; these are very bright-
sounding presets and are more appropriate for uncompressed channels or com-
pressed channels with relatively high bit rates (64 kbps or higher for the aacPlus V2
codec used in Opticodec-PC, for example).
The 8685’s sound-for-picture (TV
XXXX) presets are all conservative and will not stress
well designed codecs like Dolby AC3 and MPEG4 AAC.
The 8685 has several controls whose settings determine brightness. To minimize
brightness when using the Five-band structure:
• Use little or no high frequency boost in the equalization section.
• Set Band 4>5 coupling to 100%.
• Set the band 5 compression threshold to match the codec. Adjust the threshold
until you find a good compromise between presence and high frequency codec
artifacts. We find the range from –6.0 to +6.0 dB to be useful.
• Use a moderate Band 5 attack time. 25 ms works well.
• If necessary, lower the Band 4 compression threshold.
Starting with one of our suggested presets will help keep you out of trouble when
you edit them to create user presets.
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