Advanced Audio - Submixes, downmixing, and routing

A submix is a track that combines audio signals routed to it from specific audio tracks or track sends in the same sequence. A submix is an intermediate step between audio tracks and the master track. Submixes are useful if you want to work with a number of audio tracks in the same way. For example, you can use a submix to apply identical audio and effect settings to three tracks of a five-track sequence. Submixes can help make the best use of your computer’s processing power by allowing you to apply one instance of an effect instead of multiple instances.

Like audio tracks that contain clips, submixes can be mono, stereo, or 5.1 surround. Submixes appear as fully functional tracks in both the Audio Track Mixer and a Timeline panel—you can edit submix track properties just as you edit a track containing audio clips. However, submixes are different from audio tracks in the following ways:

• Submix tracks can’t contain clips, so you can’t record to them. Therefore, they don’t contain any recording or device input options or clip editing properties.

• In the Audio Track Mixer, submixes have a darker background than other tracks.

• In a Timeline panel, submixes don’t have a Toggle Track Output icon or a Display Style icon .

Each track contains five sends, located in the Effects And Sends panel in the Audio Track Mixer. Sends are often used to route a track’s signal to a submix track for effects processing. The submix can return the processed signal to the mix by routing it to the master track, or it can route the signal to another submix. A send includes a level knob that controls the ratio of the send track volume to the submix volume. This value is called the wet/dry ratio, with “wet” referring to the effects-processed submix signal and “dry” referring to the signal from the send track. A wet/dry ratio of 100% indicates that the wet signal is output at full strength. The submix volume affects the wet signal, and the send track’s volume affects the dry signal.

A send can be applied pre-fader or post-fader, and the outcome is that the track audio is sent either before or after the track’s volume fader is applied. With a pre-fader send, adjusting the track fader doesn’t affect the output level from the send. A post-fader send maintains the wet/dry ratio, fading the wet and dry signals simultaneously as you adjust the send track’s volume.

Whenever you route track output to a track or device with fewer channels, Premiere Pro must downmix the audio to the number of channels in the destination track. Downmixing is often practical or necessary because a sequence’s audio may be played back on audio gear supporting fewer audio channels than the original mix. For example, you might create a DVD with 5.1 surround audio, but some customers may use speaker systems or televisions that support only stereo (2 channels) or mono (1 channel). However, downmixing can also occur in a project when you assign track output to a track that has fewer channels. Premiere Pro provides a 5.1 Mixdown Type option that lets you choose how to translate 5.1 surround audio into stereo or mono audio. You can choose from various combinations of Front channels, Rear channels, and the LFE (low-frequency effects, or subwoofer) channel.

By default, track output is routed to the master track. You can also route the complete track signal to a submix track or master track by using the Track Output Assignment menu at the bottom of each track in the Audio Track Mixer. The output signal contains all properties specified for that track, including automation, effects, pan/balance, solo/mute, and fader settings. In the Audio Track Mixer, all submixes are grouped to the right of all audio tracks. You can output a track to any submix, but to prevent feedback loops, Premiere Pro allows a submix to be routed only to a submix to the right of it, or to the master track. The output menu lists only the tracks that follow these rules.