Audio Signal Flow in Final Cut Pro

When you play a sequence, you also need to hear the audio. Audio signal flow is the path audio takes from tracks in the Timeline to your speakers. Understanding signal flow helps you to properly set up audio equipment for output and monitoring. Your ability to follow the audio path also helps you to troubleshoot silent sequences or tracks that are routed to the wrong channels on an output deck.

Here is the basic audio signal flow in Final Cut Pro:

Audio Tracks

Signal flow begins in the Timeline, where you can have up to 99 audio tracks. Audio tracks contain audio clip items from clips that you have edited into your sequence. The signal from each audio track can be routed to an output bus, and multiple audio tracks can be assigned to the same bus.

Figure. Diagram showing audio clips routed to output busses.

Busses

A track is connected to a bus. A bus allows you to mix multiple audio tracks into a single signal. An output bus is typically connected to a hardware audio output on your computer or audio interface. Without busses, only one track could be connected to a physical audio output at a time, requiring you to have as many physical audio outputs as you had tracks.

For example, if you have a sequence with eight audio tracks, you can assign the output of each track to the same bus. That bus mixes the eight audio signals together and sends the combined signal to a hardware audio output so you can hear all eight tracks on a single speaker.

Each bus typically corresponds to a hardware output, so busses and hardware outputs are usually synonymous. However, you can also use output busses to group track outputs together for mixing and grouped export. Busses can be mono or stereo and can be connected to one or two hardware outputs, respectively.

Note: Busses in Final Cut Pro are used for routing tracks to hardware audio outputs or for automatic stereo downmixing. You cannot create send or auxiliary busses as you would in other audio applications.

Hardware Outputs

Hardware outputs are the physical outputs on your audio interface or any other device you connect your audio output busses to, such as the audio outputs of a DV deck. Final Cut Pro supports up to 24 hardware audio outputs.

Figure. Diagram showing an audio interface connected to speakers and other audio equipment.

By default, Final Cut Pro uses the audio output device in the currently selected Easy Setup. If you need more audio output channels or higher-quality outputs, you can connect a third-party audio interface to your computer. For more information about audio interfaces, see Connecting Professional Video and Audio Equipment. For information about choosing an audio output device for Final Cut Pro, see Configuring External Audio Monitors.

Defining Output Busses by Grouping

Output busses can be grouped together as dual mono or stereo outputs.

Figure. Diagram showing that output busses can be grouped as dual, mono, or stereo outputs.

Dual Mono Output Groups

Dual mono output groups allow you to output tracks to hardware outputs discretely. Assign a sequence track to a dual mono output whenever you want to send your audio directly to a hardware output without pan control.

Figure. Diagram showing the relationship between tracks, audio clips, and dual mono hardware outputs.

Stereo Output Groups

Stereo output groups allow you to use pan controls in the Audio Mixer to place track audio within a stereo image. Stereo output groups are useful when you want to create pan effects (such as a car passing from screen left to screen right) from mono clips or when you want to preserve the pan settings of stereo clips.

Figure. Diagram showing the relationship between tracks and stereo bus hardware outputs.

Speakers

Speakers (also called audio monitors) are devices that turn an audio signal into sound. Your computer has built-in speakers, but you can also purchase external audio speakers for higher-quality monitoring. Most speakers are sold in a stereo pair, but 5.1-channel surround sound speakers (totaling six speakers) are also becoming common.