Ambisonics is a full-sphere sound format that allows us to capture or synthesize a sound field and to reproduce it on a speaker array.
Sound files in Ambisonics format can appear in different orders. Lower order formats, such as First Order Ambisonics (FOA), can reproduce less accurate spatial representations of a sound field than high order formats, such as 7th Order Ambisonics (H7OA).
The Ambisonics order is determined by the number of audio channels that compose the sound field, each representing a spherical harmonic. More spherical harmonics result in a higher Spatial Resolution.
Before you start, make sure you check out this list of software and plugins.
Most of them are free and/or opensource and featured in all the examples shown on this page.
The ambisonics workflow is a two stages process
RECORDING/ENCODING -> DECODING
Here you will find a quick tut on how to set up the simplest ambisonics encoding-decoding chain in Reaper using IEM free plugins.
historical background
ambisonics was developed by Michael Gerzon in the 70's, in England.
A thorough documentation of Gerzon's early research has been made available online by Stephen Thornton.
A collection of Gerzon's general articles is instead available at audiosignal.co.uk