Downmixing Multiple Audio Channels to a Stereo Mix

Even when you use multiple audio channels during editing and mixing, you may need to create a stereo mix. Downmixing combines all audio output channels into a single stereo output. You may want to downmix when:

How Downmixing to Stereo Works

When a sequence is downmixed, all output busses are mixed together in a downmix stereo bus and then sent to outputs 1 and 2 on your audio interface. Stereo output busses are sent to the downmix bus in stereo; mono output busses are centered in the downmix bus.

Figure. Diagram showing the relationship between audio tracks and three busses downmixed to two channels.

Adjusting a Channel’s Downmix Volume

Each audio output bus has an adjustable downmix level that is applied only when you downmix your audio. Each audio output bus’s level is attenuated (or increased) by the number of decibels specified in the Downmix pop-up menu for the bus, in the Audio Outputs tab of the Sequence Settings window for the current sequence.

Figure. Sequence Settings showing the Downmix pop-up menus in the Audio Outputs tab.

You should use the default settings unless your stereo downmix has distortion or is too quiet. If your downmix level exceeds 0 dBFS, you may need to attenuate the downmix level of some of your output busses. If your downmix is too low, you can boost downmix levels to increase output level. Typically, the more channels you are downmixing, the more reduction is necessary for each channel to make sure the downmixed stereo signal doesn’t exceed 0 dBFS, which would cause distortion.

One of the main purposes of downmix level adjustments is to maintain mono channel levels when downmixing common 5.1-channel surround sound, for which there are industry-standard settings. After using the Match Audio Outputs command on a recognized 5.1-channel surround sound clip, industry-standard level adjustments are applied to the audio outputs’ downmix levels. You can verify these settings in the Audio Outputs tab of the Sequence Settings window.

Downmixing for Stereo Monitoring

Stereo downmixing allows you to listen to your sequence in stereo—even if the sequence has multiple output channels assigned—without changing your audio output preset.

To listen to a sequence with multiple output channels in stereo
  • Select the Downmix button in the Audio Mixer.

With Downmix selected, all audio outputs in your sequence are output as stereo whenever they’re played back, output to tape, or written to a movie file.

Figure. Tool Bench window showing the Downmix button selected.

You can turn Downmix off at any time and your audio will be output to multiple channels again. This is much more convenient than reassigning all of your tracks to a single stereo channel and then reassigning your tracks to multiple outputs again.

Figure. Tool Bench window showing the Downmix button deselected so that all channels are ouput independently.

Downmixing During Export

You can select the Downmix button to quickly export multiple audio outputs to a stereo mix without changing your audio output presets. For more information, see Audio Output Export Settings.