The Ultimate Guide to Mixing 3D Audio in REAPER with Eclipsa

Immersive audio is no longer just a futuristic concept—it is the new standard for modern content delivery. Leading this shift is the open-source IAMF (Immersive Audio Model and Formats) standard, which brings dynamic, adaptive 3D audio to everyday playback systems. If you are looking to harness this power using the Eclipsa Audio plugin suite inside REAPER, you have come to the right place. (And just a quick heads-up for search bars and browsers: it is spelled Eclipsa, not ecplipsa!)

To get the most out of a spatial mix, you need high-fidelity source material that can fill a 3D canvas. Third-order ambisonic (3OA) recordings are ideal for this, since they capture a full 360-degree sphere of sound that Eclipsa can decode and adapt to any listener's playback setup.

Understanding the Eclipsa Audio Suite

The Eclipsa system relies on a "host and satellite" model where two distinct plugins communicate with each other across your DAW. Before dropping audio onto your timeline, it is essential to understand what each tool does:

1. Eclipsa Audio Renderer Plugin (The Brain)

This plugin sits on your Master bus. It acts as the central hub for your entire immersive mix. Within the Renderer, you create the Audio Elements that every track in your project will ultimately connect to, and you define the Mix Presentation—the blueprint for how the final file will adapt to different listener setups. It also handles the 3D visual metering and processes the final export of your spatial metadata.

2. Eclipsa Audio Element Plugin (The Messenger)

This plugin is placed on your individual audio tracks. Its job is to attach that track to one of the Audio Elements already defined in the Renderer, and to stream the track's spatial data back to the Master bus in real time. Note that the Element plugin can only select an existing Audio Element from a dropdown—it can't create a new one. Audio Elements always get created in the Renderer first.

Phase 1: DAW Setup & Master Routing

Immersive audio requires a lot more data throughput than standard stereo. Let's get REAPER's engine properly configured.

1. Open REAPER and create a new project.
2. Open your Master Track FX chain.
3. Load the Eclipsa Audio Renderer plugin.
4. In the Renderer plugin's own window, click the Pin Connector button in the top-right corner. In the dialog that opens, set Track Channels to a value larger than 28—typically 32—and set VST3 bus size to match the number of speakers in your local monitoring layout. Because IAMF only uses up to 28 channels total, widening the Master bus this way guarantees your spatial data will never be choked or truncated.
5. Back in the main Renderer interface, set your "Speaker Setup" (top left) to match your physical monitoring environment (e.g., Binaural if you are mixing on headphones, or 5.1.4 / 7.1.4 if you are in a multi-speaker studio).
6. Click the Reroute button (bottom right) to open the Audio Element screen, then select +Add Audio Element and create one element for each role you'll need in this mix—for example, one Ambisonic element for a scene-based bed and one Object element for a moving mono source. Do this now: every Element plugin instance you add to a track later will need to pick from elements that already exist here.
7. Click Edit to set up your Mix Presentation, then add the Audio Element(s) you just created to it. This tells the plugin how to package the final file for target platforms like YouTube, modern TVs, or soundbars.

Phase 2: Adapting Ambisonic Recordings (The Bed)

Ambisonic recordings are the ideal canvas for an immersive mix. Unlike standard mono or stereo sounds, an ambisonic file captures a complete 360-degree "sphere" of a real-world space.

First, you must give your REAPER track enough "lanes" to hold your ambisonic data, which depends on the format's *order*:

• 1st Order Ambisonics (FOA): Requires 4 Channels
• Higher-Order Ambisonics, 2nd Order: Requires 9 Channels
• Higher-Order Ambisonics, 3rd Order (3OA): Requires 16 Channels (This is also the largest single Audio Element Eclipsa supports)

How to route your Ambisonic Bed:

1. Create a new audio track in REAPER.
2. Click the track's Route button and change the Track Channels to 16 (assuming you're working with a 3OA ambisonic file).
3. Drag and drop your 16-channel ambisonic audio file directly onto the timeline.
4. Open the track's FX chain and load the Eclipsa Audio Element plugin.
5. Click the Pin Connector button in the top-right corner of the plugin window. Set both "Track channels" and "VST3 bus size" to 32. This is not a typo—even though your source content is 16 channels, 32 is the smallest bus size that can address the full 28-channel space the Renderer is working with, and it's what Eclipsa's own documentation specifies for this plugin regardless of the element type.
6. In the Eclipsa Element interface, use the Audio Element dropdown to select the Ambisonic element you already created in the Renderer back in Phase 1.
7. Do Not Enable Panning Controls on This Track! Leave the plugin in its default Passthrough Mode. Because an ambisonic file already contains baked-in 360-degree spatial coordinates, its channels will map 1:1 onto the matching Ambisonic Audio Element automatically. Enabling the "Simple 3D Audio Panning" controls would instead try to pan the signal, collapsing the acoustic image. The Renderer on your master bus decodes the sphere to match your listener's playback hardware.

Phase 3: Spatial Automation & Mono Objects (The Movement)

With your ambient jungle bed locked in place as a beautiful 3D background, you can now place distinct sound objects—like a bird chirp or an engine pass—and move them physically through that space over the listener's head. To do this, we treat the mono track as an Audio Object and automate its coordinates.

1. Create a new track, drop your mono audio file onto the timeline, and open its FX chain.
2. Load the Eclipsa Audio Element plugin.
3. In the plugin, use the Audio Element dropdown to select the Object-type element you already created in the Renderer's Reroute panel (Phase 1). This tells the master Renderer that this is a pinpoint sound requiring exact directional data.
4. Enable the plugin's panning controls so you can position and automate the object—consult the plugin UI for the exact toggle, as this varies slightly between plugin versions.
5. Go to your track control panel in the REAPER arrange view and click the Env (Envelope/Automation) button.
6. Scroll down to the Eclipsa parameters and check the boxes for whichever spatial coordinates the plugin exposes for panning (typically some combination of Azimuth/Elevation/Distance or X/Y/Z, though it's worth confirming the exact labels in your installed version). Close the window to display the automation lanes beneath your track.

Two Ways to Move Your Object:

Method A: Drawing Precise Paths
Hold Shift and click directly on an automation lane to create keyframe nodes. Create multiple nodes and drag them up or down to create precise linear sweeps (e.g., sweeping Azimuth from bottom to top to move a sound smoothly from the far left of the room to the far right).

Method B: Live Performance Tracking
Right-click the track's Env button and change the automation mode from Trim/Read to Touch or Write. Open the Eclipsa Audio Element plugin UI so the panning coordinate window is visible. Press the Spacebar to play your project, grab the panning puck inside the plugin window with your mouse, and physically drag it around. REAPER will record your movements live onto the timeline. Important: Always change the mode back to Read when you are finished so you don't accidentally overwrite your hard work on subsequent playbacks!

Phase 4: Exporting Formats & The "Render Handshake"

When working in immersive formats, you cannot simply perform a standard stereo bounce. You are packaging audio files alongside an intricate web of metadata. Inside the Renderer's Export screen, you'll find these options:

• File Format: Choose between IAMF (your high-fidelity spatial master, containing all audio elements, ambisonic beds, automation paths, and presentation data) or WAV.
• Export audio elements as WAV: Exports your discrete audio elements as individual stem files alongside your master file—highly recommended for safety backups and future re-mixes.
• Video muxing: For deliverables that need picture, Eclipsa can mux your finished spatial mix into a video file. As of this writing, REAPER exports support QuickTime (.mov) for the muxed output rather than .mp4—the documented workflow is to export your video pass first, then run the mux as export. Eclipsa is actively-developed open-source software, so it's worth double-checking the exact supported container in your installed version before you build a delivery pipeline around it.

Executing the Final Render

Because the Eclipsa Renderer plugin acts as the encoder, you must initiate a simultaneous "handshake" render between the plugin and REAPER.

1. Open the Eclipsa Audio Renderer plugin on your Master bus and click the Export button.
2. Check the box labeled "Export audio".
3. Under "Save Audio To," browse to your desired folder on your hard drive and give your file a clear name.
4. Optional: If you are rendering for video, follow the mux workflow to bring in your already-exported video pass.
5. Leave the plugin export window open. Go to REAPER's top utility menu and select File > Render.
6. Configure your REAPER render bounds (e.g., "Entire project" or "Time selection"). Set your sample rate to match your project (ideally 48kHz for video assets).
7. Click Render 1 file inside REAPER. As REAPER runs through the timeline to print its audio, the Eclipsa Renderer plugin captures the stream, encodes the spatial metadata tracks, and builds your final file seamlessly in the background.

Conclusion & Next Steps

You have successfully built an advanced, adaptive 3D soundscape from scratch! By utilizing scene-based background beds and highly automated sound objects, your mix will now dynamically adapt to give your listener the best possible spatial experience, whether they are on budget headphones or sitting in an expensive home theater setup.

If you are ready to expand your spatial pallet, experiment with new workflows, or dive into ambisonic capture techniques, check out the specialized tutorials and high-resolution spatial sound libraries available at Axis Ambisonic Lab.