The Multi-Band Structure - Orban OPTIMOD 6200 Operating Manual

Digital audio processor

Table of Contents

3-26

OPERATION

ing is increased, the audible distortion caused by limiting is increased. Lower settings

reduce loudness, of course, but result in a cleaner sound.

You may find it illuminating to recall several Factory Presets, adjust LESS-

MORE to several points in its range, and then open the Full Control screen

to examine the trade-offs between the release time and

made by the factory programmers.

LC THRESH (Loudness Controller Threshold) sets the maximum subjective loudness

produced by the processing. "0" is a good setting for most DTV programming to ensure

that even highly processed commercials will not be objectionably louder than surround-

ing program material.

Because this is a threshold control, turning it to higher numbers raises the threshold,

which means it does less work.

According to CBS Laboratory's research, no common meter, whether peak-reading, av-

erage-reading, or even r.m.s.-reading with frequency weighting, can indicate subjective

loudness well enough to be relied upon as an objective measurement tool to prevent

viewer complaints about loud commercials. True loudness meters incorporate elaborate

multiband psychoacoustic models, which agree with average listeners with an accuracy

of typically ±2dB. Because listeners will disagree amongst themselves by as much as

4dB when asked to assess the loudness of a piece of program material by comparison to

a standardized tone or filtered noise, ±2dB is about as much accuracy as is usable any-

way. This also means that a peak-reading or average-reading meter connected to the

6200's output (with Loudness Controller activated) may vary quite a bit in its readings

with different program sources. This just shows the Loudness Controller at work and the

inability of a conventional meter to accurately assess loudness.

Note that the Loudness Controller determines the highest subjective loudness permitted

by the 6200 processing. If a commercial follows a piece of quiet program material whose

loudness never gets to the threshold of the Loudness Controller (for example, a quiet

outdoor scene), then the following commercial will still be louder. Esthetically, this is

unavoidable. The best one can do by automatic control is to ensure that commercials are

no louder than normally modulated sections of programming that surround the commer-

cials.

To defeat the loudness controller entirely, set the

gramming, you will usually want to defeat the loudness controller.