Downmix Audio Filter

Converts multi-channel audio into a single mixed signal and outputs that signal uniformly to the project’s configured output channels.
All input channels are summed together without regard to channel role or frequency content.

Downmix is a channel-routing and summing filter, not a spatial or frequency-aware processor.

What this filter does

• Sums all input channels into one mono signal
• Sends the same mixed signal to the selected output channel(s)
• Does not preserve surround positioning, center emphasis, or low frequency (LF) separation
• Does not perform weighting, panning, or frequency-based routing

This is a direct channel-summing operation, not a surround-aware conversion.

Parameters

Target channels

Selects which output channel(s) receive the down-mixed mono signal.

Note

Available buttons depend on the project’s audio channel configuration:
Settings > Audio Channels

Typical targets include:

• L / R — Front left and right
• C — Center
• LF — Low-Frequency Effects (LFE)
• Ls / Rs — Surround left and right

The same mono signal is sent to the selected target channel(s).

Channel selection behavior (source-dependent)

When the Downmix filter is applied:

• If the project uses more than two audio channels but, for instance, the source clip is stereo (2 channels):

  • L and R target channels are selected automatically
  • Other channels (C, LF, Ls, Rs) are not selected by default
    
  • All target channels remain manually selectable

This default reflects the source channel layout rather than the project layout.

Note:

The filter does not up-mix automatically. Only channels present in the source are preselected; additional target channels must be enabled manually.

Channel behavior and limitations

• All input channels are treated equally and summed together.
• The filter does not:
  • detect dialogue
  • prioritize the center channel
  • isolate bass for LF
  • apply loudness compensation
• Output level depends on the combined input level and may require gain adjustment downstream.

Auditory characteristics

• Audible collapse of spatial separation
• Identical signal on selected output channels
• Surround information is lost
• Potential increase in overall level due to summing

Typical use

• Typical use cases include routing down-mixed stereo recordings to the Center channel for dialogue or spoken voice, or targeting the LF channel for bass-heavy material such as effects or music.

Recommended use cases

• Converting stereo audio to mono
• Creating dual-mono output (same signal on left and right)
• Preparing dialogue tracks for center-channel placement
• Routing summed audio to LF for bass-heavy material
• Simplifying complex channel layouts for compatibility

Usage notes and tips

• After down-mixing, use Gain / Volume or Limiter to control output level.
• When targeting the Center channel, this filter is useful for spoken content.
• When targeting LF, ensure the material is appropriate for low-frequency playback.
• For surround-aware or weighted down-mixing, use dedicated mixing workflows instead.

Limitations

• No channel weighting or intelligent mixing
• No frequency-aware routing
• No preservation of spatial cues
• Can cause clipping if summed levels are high