Ambisonics Workflow
When it came to mixing in 3D audio, I decided to begin my first immersive mixing experiments using Ambisonics in Reaper rather than Dolby Atmos. This decision was mainly influenced by the IEM Plugin Suite, which provides intuitive and flexible tools for Ambisonics mixing and made the initial entry into 3D audio more accessible.
I chose to work with fifth-order Ambisonics for this project to achieve a more accurate and immersive rendering of diffuseness, spaciousness, and spatial depth. While first-order Ambisonics might seem sufficient due to the even nature of diffuse sound fields, in practice, their low spatial resolution leads to high directional correlation during playback, which significantly impairs the perception of these spatial qualities. Higher-order Ambisonics, in contrast, improves the mapping of uncorrelated signals and preserves spatial impressions much more effectively. Psychoacoustic research has shown that an Ambisonic order of three or higher is required to perceptually preserve decorrelation between neighboring loudspeakers, which is crucial for rendering depth and diffuseness. Fifth-order Ambisonics further enhances this, particularly outside the sweet spot, providing a more consistent spatial experience across a larger listening area. As demonstrated in the IEM CUBE, a fifth-order system allows nearly the entire horizontal listening plane—in this case, a 12 × 10 m concert space—to become a valid and perceptually plausible playback zone. [1]
Thus, fifth-order Ambisonics is not only a practical choice for immersive production in larger spaces, but it also strikes an effective balance between spatial resolution, technological complexity, and perceptual benefit [2].
I also had the opportunity to experience this myself during a small listening test we conducted with Matthias Frank. We listened to first-, third-, and fifth-order Ambisonics in a blind comparison and were asked to rate certain spatial parameters like spatial depth or localization. The first order was quite easy to identify due to its limited spatial resolution. However, distinguishing between third- and fifth-order Ambisonics proved to be much more challenging, as the differences were often subtle and less immediately perceptible.
After that, I started with setting up the routing, which was one of the most underestimated parts of this project. Similar to a traditional stereo production, I created a structure of groups and subgroups, but adapted it for Ambisonics. For example, in the drum section, encoding happens at the main drum group via the IEM Multi Encoder. All individual channels are routed into that group, allowing me to process them using conventional stereo plugins before spatializing them — saving both CPU resources and maintaining flexibility in the early mixing stages.
Within the drum routing, I created subgroups for kick, snare, overheads and the “Droom”, allowing for finer control and processing. When dealing with coherent signals, such as double-tracked guitars, I first routed both signals (panned hard L & hard R) into a stereo group to conserve CPU power by processing them together. This group is then routed into a master guitar group that handles Ambisonics encoding. Since the L and R signals remain separated, they can still be treated independently in the encoder and placed individually in the 3D field.
I followed the same approach with vocals, organizing them into groups before routing them into the Multi Encoder. For specific adlibs, I used the Granular Encoder to create glitchy, scattered spatial effects.
To add a sense of depth and immersion to the vocals, I used a small amount of FDN Reverb for diffuse reverberation and the Room Encoder for early reflections — all plugins from the IEM Suite.
Finding this optimal signal flow took considerable time and experimentation. It was a major learning process to understand how to best structure a large session for Ambisonics.
References
[1] Franz Zotter and Matthias Frank, Ambisonics: A Practical 3D Audio Theory for Recording, Studio Production, Sound Reinforcement, and Virtual Reality, Springer Topics in Signal Processing (Springer International Publishing, 2019), 19:18–20, https://doi.org/10.1007/978-3-030-17207-7.
[2] Zotter and Frank, Ambisonics, 19:18–20.
