Introduction⌗

Surround mixing allows you to create immersive audio by distributing sounds across multiple speakers. Whether you’re building a cinematic soundscape, crafting 3D audio for installations, or designing game sound, Reaper’s flexible routing system makes it a powerful tool for multi-channel mixing. In this post, we’ll explore key techniques, from configuring multi-channel output and mapping channels to working with Sound Particles, automating surround panning, and rendering video with surround audio.

Distributed Sources⌗

One of the simplest ways to begin with surround mixing in Reaper is to send a mono or stereo track to all speakers. First, ensure that both your track and master track are using 8 track channels. You can adjust this by clicking the routing button for each track and setting the track channels to 8.

Once your outputs are set to multi-channel output, your setup should look like this:

Multi-channel routing
Track routing for multi-channel output in Reaper

Try playing back any mono or stereo track with these settings. You’ll now hear the sound across all speakers.

Adding a Multi-Channel Track⌗

To route a multi-channel track to specific speakers, configure its channel outputs. For example, to send audio only to the side speakers, use channels 7 and 8 in your routing matrix.

Try with freesound multi-channel files to experiment with different speaker configurations.

Using Sound Particles⌗

Sound Particles is a powerful tool for creating audio files encoded with spatial data. It allows you to design sounds that move dynamically in a 3D space. For example, you can take a simple recording—like a cat’s growl—and use Sound Particles to move it through your mix environment.

Here’s another idea: I used Sound Particles to create an immersive fire soundscape. Starting with a basic fire recording, I applied the immersive fire preset, which automatically places the sound around the listener. Export your spatial audio from Sound Particles, then import it into Reaper as a multi-channel file to experience it in your surround mix.

Extending Channel Mapping with ReaSurroundPan and Automation Items⌗

You can achieve sophisticated channel mapping and modulation using ReaSurroundPan for surround control. This tool lets you pan audio dynamically across multiple speakers, with full automation support for creative modulation.

Steps for ReaSurroundPan Setup and Automation⌗

  • Add ReaSurroundPan to your track and select the appropriate surround preset (e.g., 5.1 or 7.1).
  • Route your audio to different channels using ReaSurroundPan’s interface. For example, set the X and Y coordinates of your input channels to align with your speaker arrangement.

ReaSurroundPan
Speaker arrangement view in ReaSurroundPan

  • Reveal the panning parameters for automation by clicking the param button in the ReaSurroundPan interface and selecting ‘show track envelope’.
  • Insert an Automation Item: Right-click on the timeline and select Automation Item → Insert New Automation Item. Use the LFO editor to create custom panning shapes, such as sine waves or square pulses.
  • Experiment with LFO parameters such as skew, pulse width, and phase for creative modulation.
  • Combine multiple automation items: For advanced movement, use several automation items across different parameters (e.g., X, Y, and width) to simulate complex trajectories, such as circular panning patterns.

This approach gives you fine-grained control over how sound moves through the space, making it ideal for immersive audio applications like game audio or installations.

Recording Automation⌗

To add automated movement to your panning, use ReaSurroundPan’s automation features:

  1. Find the automation parameters for input channels 1 and 2 (X and Y coordinates).
  2. Arm these parameters and set the automation mode to Write.
  3. Play your session and move the parameters to record automation in real time.
  4. Set the automation mode back to Read once you’re finished to prevent unwanted overwriting.

Here’s how you can use preset pan moves:

Pan moves
Preset pan moves in ReaSurroundPan

For example, the ‘To Left Front’ preset moves both pucks toward the front left speaker when increased. This simplifies automation by controlling movement with a single parameter.

Pro tip: If you’re working with height channels, experiment with Z-axis shapes to control vertical movement.

Panning Multiple Point Sources⌗

You can combine multiple sources into one track and control them as if they were part of a single multi-channel track:

  1. Send multiple sources to a single track and route each one to a different track channel.
  2. Use ReaSurroundPan to automate and pan these sources as a cohesive unit.
  3. Rename tracks in ReaSurroundPan to stay organized.

Surround mixing
Managing multiple sources in ReaSurroundPan

Rendering Video with Surround Audio⌗

To export your surround mix, follow these steps:

  1. Go to Options → Channels → 6 to configure your output for 5.1 surround.
  2. Select an appropriate video format that supports multi-channel audio (e.g., AVI or MP4).
  3. Render your project, ensuring all audio tracks are routed correctly to match the surround format.