Downmixing; Loro And Ltrt; Downmix Settings - Calrec SUMMA User Manual

DOWNMIXING

When a surround audio feed is routed to a mono or stereo destination, its component legs are combined using predefined
level settings to ensure the resultant mono or stereo feed is accurate and appropriate. This process is referred to as
downmixing.
Downmixing happens automatically whenever a surround feed is routed to a non-surround destination. All internal
downmixing uses LoRo values.

LoRo and LtRt

When configuring a 5.1 main there are two sets of downmix options available: LoRo and LtRt. LoRo is simply the surround
channels summed together as follows:
• L + Ls+ C = Lo
• R + Rs + C = Ro
LoRo takes away all front to rear sound separation and leaves a stereo mix which is also compatible with mono systems.
LtRt uses phase processing prior to summing channels together to provide a stereo mix which is compatible with Dolby
Pro Logic systems and can be decoded to recreate the original 5.1 mix. LtRt feeds are not mono-compatible.
Note: When a 5.1 main is set for Lt/Rt, only the downmix audio that is patched out of the Summa system is phase
encoded. All internal routing of the 5.1 main to stereo destinations remains as LoRo.

Downmix Settings

Individual LoRo downmix settings are available for each surround path from the fader control window. Five level
controls are available: Left and right front (LR), centre (C), low frequency effects (LFE), left and right rear (LsRs) and
an overall level control (overall LoRo). Altering the overall LoRo level increases and decreases the overall level of the path.
Individual, path-specific downmix level controls are not available for LtRt, instead the default values set within the Show
settings are used.
FIGURE 1 - DOWNMIX FADERS
CALREC
Putting Sound in the Picture
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