An overview and explanation of the upmixing controls.
The controls in the Basic menu can be divided into four basic groups: Format controls (1A), LFE Channel controls (1B), Center Width controls (1C), Gain controls (1D), and Auto-Detect controls (1E).
Figure 1 - Basic UPMAX control grouping
Format Controls
Input Format
The Input Format menu (2A) is used to specify the channel format of the source audio. If the input format matches the selected output format (as selected with the Output Format control) the unit will pass the signal through as-is without additional processing. Input options include:
Auto Detect: In this mode, the unit continuously monitors the input signal to determine its format and will automatically switch to one of the processing modes below (Stereo, Stereo + Dialog, or 5.1)
Stereo: Stereo content will be upmixed to the desired output format
Stereo + Dialog: Stereo content will be upmixed to the desired output format, while a dedicated dialog input on Channel 3 will be passed through to the Center output
5.1: 5-1-channel content will be upmixed to the desired output format
Pass-through: Pass-through will pass the input signal directly through to the output with no additional processing; this can be used as a “soft bypass” function as the signal still runs through the upmixer and therefore incurs the same amount of latency as it would if it was actually upmixing a signal, thereby preserving A/V sync and avoiding lip-sync issues
When Auto Detect is selected, enabling the Center Detect control (2B) upmixes stereo content to the specified output format but ignores the presence of audio on Channel 3, which is typically dialog. The Channel 3 audio is time-aligned and summed with the upmixed version of the audio at the output. This is especially useful in sports production where announcer dialog is often routed on a separate bus, giving downstream facilities the option to edit or replace the announcer track.
Output Format
The Output Format menu (2C) determines the output channel configuration. Output options include:
5.1: Provides a constant 5.1-channel output from Stereo, Stereo + Dialog, and 5.1-channel input sources.
5.1 Legacy: Like the standard 5.1 output, it provides a constant 5.1-channel output from Stereo, Stereo + Dialog, and 5.1-channel input sources but with upmixing that is sonically closer to the previous UPMAX algorithm used in the Linear Acoustic UPMAX v4 upmixer and the algorithm employed in the various Linear Acoustic AERO®-series processors.
7.1: Provides a constant 7.1-channel output from Stereo, Stereo + Dialog, 5.1-channel, and 7.1-channel input sources.
7.1+2: Provides a constant 7.1.2-channel output from Stereo, Stereo + Dialog, 5.1-channel, 7.1-channel, or 7.1.2-channel input sources.
5.1+4: Provides a constant 5.1.4-channel output from Stereo, Stereo + Dialog, 5.1-channel, or 5.1.4-channel input sources.
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Figure 2 - Format controls
LFE Channel Controls
The LFE channel controls are used to tune the crossover frequencies, gain, and signal routing of the low-frequency effects audio.
LFE Filter Frequency
The LFE Filter Frequency control (3A) defines the frequency at which audio below the setting is routed to the LFE channel and audio above is sent to the Lf, Rf, C, Ls, and Rs channels. The crossover is typically set at 80, 100, or 120Hz; the default is 80Hz. This control works in combination with the LFE Routing and LFE Gain controls to create the LFE Channel.
LFE Gain
The overall gain level of the LFE channel is set by the LFE Gain control (3B). When set to 0.0dB, the same amount of gain below the frequency set in the LFE Filter Frequency control (3A) present in the original 2-channel audio (and, in turn, the total gain in all lateral channels after upmixing) will also be added to the LFE channel.
LFE Routing
The LFE Routing control (3C) balances the amount of LFE content (audio below the LFE Crossover Frequency setting) sent to the LFE channel versus what remains in the Lf, Rf, C, Ls, and Rs channels.
Setting this control to 0.50 sends 50% of the audio to the LFE channel and leaves 50% in Lf, Rf, C, Ls, and Rs channels. A setting of 0 sends no audio below the crossover frequency to the LFE channel, while a setting of 1 sends all audio below the crossover frequency to LFE channels, effectively removing it entirely from the remaining channels.
Figure 3 - LFE channel controls
Center Width Controls
These controls define the routing of the Center channel LF and HF bands across the Left, Center, and Right channels. Used in combination with the Mid-Bass Crossover frequency control, they provide the ability to craft the image of the Front channels in a way that maintains a direct sonic-visual association of dialog while providing a pleasant and wide image of the phase-correlated elements. Values are expressed in a decimal format but easily correlate to a percentage value (0.00 = 0%, 0.50 = 50%, 1.00 = 100%, etc.).
The LF Center Width control (4A) determines the amount of LF audio routed to the Center versus the Left and Right Channels.
The HF Center Width control (4B) does the same for audio in the HF band.
A setting of 0% sends all audio in the respective band to the Center channel, while a setting of 100% sends audio to the Left and Right channels only. Intermediate values provide a blend to create any desired mix.
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Figure 4 - Center Width controls
Gain Controls
The Center Gain control (5A) and Surround Gain control (5B) set the overall output gain of the center and surround channels respectively. The default value of 0dB for both controls will result in a downmix that adheres to Dolby's standard recommended settings.
The Master Gain control (5C) simultaneously sets the output gain of all channels.
Important: The settings of the Center Gain and Surround Gain controls have an important impact on the downmixed signal. Please read and understand the Upmixing Controls That Affect the Downmix section before adjusting these settings.
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Figure 5 - Gain controls
Auto-Detect Controls
When the Input Format is set to Auto-Detect, the UPMAX ISC continuously monitors the input signal to determine its format and will automatically switch between upmixing to the selected Output Mode and pass-through.
The level at which the detector circuit determines that the incoming signal is program audio (and not noise or silence) is set by the Auto-Detect Threshold control (6A). The proper setting depends largely on the quietness (or noisiness) of channels that are not muted but also contain no audio. Set too low, it may cause a false trigger to upmix; set too high, it may cause a late transition to upmixing. The default value of -70dB should work well for modern production while values as high as -63dB may be required for noisy sources.
The amount of time in milliseconds a signal must stay above the Auto-Detect threshold before the unit begins upmixing - or below the threshold to cease upmixing - is determined by the Input Switch Transition control (6B). A value between 10ms and 12ms is a good starting point for most material.
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Figure 6 - Auto-detect controls