How to Work With Ambisonics: Workflow From Recording to Delivery

This page describes the complete Ambisonics workflow — from microphone placement to finished delivery or live system. It is not a beginner tutorial, but a reference for practitioners: compact, decision-oriented, and aligned directly with the ICST ecosystem.

Microphone Selection

Ambisonics microphones record in A-Format — the raw capsule signals, not yet a sound-field format. Conversion to B-Format (ambiX) happens afterwards, either internally in the microphone or via software.

Rule of thumb: 1st-order microphones are sufficient for FOA productions and teaching. For HOA productions from 3rd order up, a Zylia ZM-1 or EigenMike is appropriate.

A-to-B Conversion

The conversion matrix compensates for capsule spacing, frequency response, and phase errors of the specific microphone. Manufacturer-specific matrices matter — not all A-to-B tools work with all microphones.

• Import A-Format raw file into REAPER (4 / 19 / 32 channels depending on microphone)
• Load manufacturer-specific A-to-B plugin: Sennheiser Ambeo Orbiter, SoundField Ambisonic Toolkit, or ICST JS Plugin
• Verify channel assignment: W (pressure) on channel 1, then X, Y, Z following ACN ordering
• Audition a short test segment binaurally — confirm stable directionality and coherent depth
• Export result as ambiX WAV and document metadata (microphone, location, take number)

Field Recording Workflow

Common Problems and Solutions

Session Architecture in REAPER

A clean Ambisonics session has a clear hierarchy:

Source Tracks (Mono / Stereo / A-Format)
   └→ ICST AmbiEncoder (Encoding + Panning)
        └→ HOA Bus (B-Format, N channels)
             ├→ Decoder Track → Speaker Output
             └→ B-Format Master → Export

Routing Step by Step

• Create HOA Bus: channel count matching desired order (4 / 9 / 16 / 25 / 36 channels)
• Insert ICST AmbiEncoder on every source track: set azimuth, elevation, spread
• Route encoder output to HOA Bus — never directly to master
• Insert ICST AmbiDecoder at the end of the chain: load speaker layout preset
• Build a separate binaural branch: AmbiHeadphone on its own monitoring track
• Prepare B-Format Master as a separate render track (without decoder)

Spatial Mixing — Parameters

Reverb and FX

Place reverb and room effects after the encoder and before the decoder — not on individual source tracks. This keeps room sound format-independent and ensures it is correctly exported with the B-Format master.

Typical chain for an HOA reverb:

Source Track → AmbiEncoder → [HOA FX: SN3D-compliant Reverb] → HOA Bus → Decoder

Monitoring

• Binaural: AmbiHeadphone on a dedicated monitor track, solo routing.
• Speakers: ICST AmbiDecoder with the preset for the current room.
• Preset switching: Only swap the decoder — the HOA bus remains unchanged.

Choosing HOA Order

Golden Rule: Always Render from the B-Format Master

Export Workflow

• Solo the B-Format master track and disable all other outputs
• Render a short test file (approx. 10 s) and re-import it
• Audition the test file through the binaural path — confirm spatial coherence
• Start the full render: WAV / RF64 for large multichannel files
• Document metadata in the project notes

Recommended meta-text for REAPER Project Notes:

Render: B-Format Master | Format: ambiX (ACN/SN3D) | SR: 48000 Hz | Bit: 32-bit float | Channels: 16 | HOA: 3rd | Monitoring: Binaural ✓ / Array ✓

Format Decisions

Channel Count by HOA Order

Export Checklist

• B-Format master track confirmed as source
• Channel count matches HOA order
• Sample rate: 48 kHz
• Bit depth: 32-bit float (master) or 24-bit (delivery)
• Format: ambiX (ACN/SN3D) documented
• Filename includes order and format
• Test render before full export
• Re-import and binaural check passed
• Project notes updated
• B-Format archive copy backed up

Core Question: Where Does Decoding Happen?

The most important decision in live HOA systems is decoder placement:

System Design by Context

Max/MSP for Live HOA

• Load externals: ambiencode~, ambidecode~, ambipanning~ from the ICST Max tools
• Generative panning: drunk, noise~, or cycle~ feeding azimuth and elevation inputs
• OSC routing: control spatial parameters over the network (tablet, sensor, external software)
• Load speaker preset into ambidecode~ and send a test tone through all positions
• Stress-test for continuous operation: patch must run stably for hours without memory leaks or crashes
• Prepare a backup patch: switch to binaural stereo if the array fails

OSC Control

OSC messages to the ICST AmbiEncoder enable real-time positioning from external sources — tablet, sensor, another piece of software, or a second device.

Key preparation:

• Document OSC port and message namespace in the REAPER template.
• Test latency: OSC over UDP is unconfirmed delivery; for critical messages, consider confirmed transmission.
• Fallback: REAPER automation lanes as backup if OSC fails.

→ Full OSC syntax reference: OSC Syntax for the ICST AmbiEncoder

Irregular Arrays and AllRADecoder

For irregular speaker layouts (non-spherical, asymmetric), the AllRADecoder from the IEM Plugin Suite offers more flexibility than the ICST decoder. Workflow:

• Enter speaker positions into AllRADecoder and compute the decoder matrix.
• Export the matrix as a preset and load it into the live patch.
• Always measure with the real setup — do not rely on simulation alone.

Quick Reference: Decision Guide

Further Resources