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Acoustical Parameters - Introduction
While the SSD-66 (5.1)'s Global Parameters, once set, are constant regardless of Input Label
selection. Thus these parameters, will remain unchanged as you proceed to set the Acousti-
cal Parameters for each Input Label that you are using.
The SSD-66 (5.1) is uniquely flexible in that each Input Label has its own set of Acoustical
Parameters which include the following:
Input Labeling - Each Input Label, numbered 1-14, has a programmable nine character label
which can be easily altered. Thus, if an existing Input Label is an inaccurate de-
scription of the source component, you can alter the name of the Input Label to suit
your installation.
Active Speakers - The speaker channels that are going to be used can be independently set
per Input Channel. For example, while all speakers will be used for a VCR (Pro
Logic mode), only the front two speakers may be active for a CD PLAYER (Stereo
mode).
PCM Scale - The term PCM (Pulse Code Modulation) typically refers to the digital stereo
audio channels (PCM Stereo) on laser discs and CDs. For this reason, the Input
Label for non-AC-3 formatted laser disc source material is labeled "LASER PCM".
The term PCM Scale refers to the relative volume level based on a scale from 0-
255. The standard PCM Scale setting is "127". This represents the highest volume
level (most bits) which can be set using the PCM Scale as a volume contour con-
trol. Thus using "127" as the high point, volume will decrease as you either lower or
increase the PCM Scale from the center "high point" value of 127. Please note,
that when using the PCM Scale as a volume control, the reduction of volume level,
as you increase or decrease from "127", is a result of the processor skipping bits.
Since bits represent audio information, PCM Scale settings other than "127", will
also result in some data loss. The PCM Scale can be individually set per Input
Label. Thus, source input levels can be individually adjusted using the PCM Scale.
This may result in a loss of information and should only be used if volume level
balancing per input is absolutely essential.
THX Re-Equalization (Primarily for Film Soundtracks) - Home THX Controllers decode the
audio track signals using Dolby's Pro Logic or digital 5.1 channel circuitries (AC-3 &
DTS). This is precisely how it's done in the dubbing stage monitoring system during
the original recording. However, unlike other systems which simply amplify and
reproduce the resulting soundtrack channels, Home THX applies unique enhance-
ments before these decoded signals are reproduced.
"Re-equalization," compensates for the effect of reproducing sounds in a smaller
room that have been originally processed for a large movie theatre with high-fre-
quency equalization. Without this process, the sound levels would be skewed to-
ward the higher frequencies, making the sound seem overly "hissy" or brilliant.
Unlike a large theatre, the smaller video-viewing rooms in a home would not acous-
tically attenuate those "highs." Home THX Re-equalization restores the original
response characteristics before the signals are amplified and used to drive loud-
speakers.
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