My colleague Brian Fallon has recently created a First-Order Ambisonic Encoder Reaper plugin for the Zoom H2n portable recorder which you can download from the link below;
While the H2n is far from the best Ambisonic microphone available, it is certainly one of the most affordable and produces surprisingly usable results given its cost (although due to the geometry of the H2n’s microphone capsules, it is horizontal only). Zoom released a firmware update for the H2n earlier this year which allows for horizontal only Ambi-X audio to be recorded directly onto the recorder. However, it can sometimes to be useful to record in the original 4-channel mode (so you have access to the original stereo tracks) and convert to Ambisonics later. In addition, if you made 4-channel recordings with the H2n prior to the release of this Firmware update, then this plugin can also be used to convert these into Ambisonics.
Brian’s plugin is for the DAW Reaper and can be used to convert these H2n 4-channel recordings into horizontal B-format Ambisonics and also allows you to choose various output channel orders and normalization schemes (Furse-Malham, Ambi-X, etc.). The package includes a sample Reaper project and a manual with details on the recording and plugin setup.
Note, that if you own the older H2 recorder which has a slightly different microphone arrangement, then Daniel Courville’s VST and AU plugins can be used for conversion to B-format in a similar fashion.