Ambi Decoder Stereo

s3g Ambi Decoder Stereo decodes ACN/SN3D ambisonic input to a true stereo output using virtual speaker fields and practical stereo pickup models. It is for loudspeaker-style stereo monitoring or stereo renders, not headphone binaural playback.

Workflow

Insert s3g Ambi Decoder Stereo after the encoded source and any Ambisonic processing, then match ORD to the incoming field.
Route its true stereo outputs to a monitored stereo master or loudspeaker destination, then begin playback.
Choose a virtual FIELD and stereo pickup MTHD while audio is playing.
Adjust rotation, width, directivity, diffuse blend, weighting, and output level for the intended stereo image.

Model

The decoder projects the ambisonic signal onto a virtual speaker field, then derives stereo from that field using a selected pickup method. This makes the signal path readable: first choose how the ambisonic field is sampled, then choose how the stereo image is derived.

Available virtual fields include quad, 8-channel cube, 12-channel dodeca, 24-channel dome, and 32-channel sphere. These are internal sampling fields, not necessarily the user's physical speaker layout.

Pickup Methods

XY cardioid: coincident angled cardioid-style pickup.
ORTF-style: spaced and angled cardioid-style pickup. It suggests ORTF behavior but is not a measured physical microphone model.
MS cardioid: mid/side pickup, displayed as M, S+, and S-.
Blumlein: crossed figure-8-style pickup with dashed negative lobes in the display.
Spaced omni: A/B-style pickup. The AB control changes capsule spacing and is visualized in the field.
Dual shotgun, Wide cardioid, Supercardioid XY, Hypercardioid XY, and Height focus: alternate pickup shapes for comparison.

Controls

Control	Meaning
ORD	Ambisonic order, from `1OA` to `7OA`.
FIELD	Internal virtual field used for projection.
MTHD	Stereo pickup method.
WDTH / ANG / ROT	Stereo width, pickup angle, and listening rotation.
DIR / REAR / HGT / DIF	Directivity, rear rejection, height fold, and diffuse blend.
WGT / AGN	Ambisonic order weighting and output autogain.
AB	Spacing for `Spaced omni`.
BASS	Optional bass mono fold below the selected frequency.
M-EL	Microphone elevation for pickup models that use vertical orientation.
OUT	Final output gain.

REAPER Routing

This plugin exposes a true stereo output bus. In REAPER, a multichannel track can still preserve audio on higher track channels that are not mapped through the plugin output. If a following meter shows channels above 2 after the decoder, open REAPER's plugin pin connector and enable Zero out unmapped output channels.

For headphone-style monitoring, use Ambi Decoder Head. For speaker layout playback, use Ambi Decoder Speaker 64.