Ambisonic Cheat Sheet

Welcome to this breakdown on Ambisonics. It is increasing in popularity and use but still poses a challenge to learn and understand.

Many terms are thrown around: a-format, b-format, spherical harmonics, ambisonic order, spatial audio, and many more. Moreover, how the technology is explained depends on whether you are using physical microphones or creating ambisonics in a DAW, adding to the confusion.

This cheat sheet should cut through the confusion and make it easy to understand.

Ambisonics In Its Simplest

Ambisonics is a channel-based format where each channel maps to a different direction. For example, a simple ambisonic file will use three channels to map the directions left and right, up and down, forward and back; on top of these directions, one additional channel maps to an Omni directional signal. If you are familiar with mid-side signals, then this channel is the 'mid'.

If there is anything to take away and ingrain, it is the information above.

Each channel maps to a direction.

Ambisonic Order

Terms like '1st order' and '5th order' relate to the number of channels in the ambisonic file. 'Higher order' is a shorthand way of referring to orders of 3rd or above.

  • 1st Order = 4 channels
  • 2nd Order = 9 channels
  • 3rd Order = 16 channels
  • 4th Order = 25 channels
  • 5th Order = 36 channels

A-Format Versus B-Format

B-format is the easiest to understand: it is the format explained in the points above where each channel maps to a direction.

However, b-format is hard to record in the real world. The solution is using special microphones and encoding the resulting signals into b-format. The raw format from the microphone is called a-format.

FuMa Versus AmbiX

FuMa and AmbiX are two ways of describing the order of channels in an ambisonic file. AmbiX is used more than FuMa.

How To Create Ambisonic Files

Reaper is the best choice for sound designers in the gaming industry. Using IEM and SPARTA, Reaper's high channel count allows for the easy creation of ambisonic files.

Middleware Support

FMOD has support for 1st order ambisonics with Google Resonance and other such plugins. However, Wwise proves to be the best middleware for the technology, supporting 5th order ambisonics natively.