Ambi Decoder Head

s3g Ambi Decoder Head decodes ACN/SN3D ambisonic input to stereo using a synthetic head model. It can run as a headphone-style binaural monitor or add a transaural crosstalk-cancellation stage for stereo loudspeakers.

Workflow

Insert s3g Ambi Decoder Head after the encoded source and any Ambisonic processing, match ORD to the incoming field, and choose Binaural or Transaural monitoring.
Route its true stereo outputs to headphones in Binaural mode or to the stereo loudspeaker destination in Transaural mode.
Choose the decoder path and head profile while audio is playing.
Adjust listener orientation, width, pinna influence, room blend, and output level for the monitoring setup.

Model

The decoder uses short interaural delays, head-shadow filtering, and pinna and width controls to create a synthetic head response. It does not load measured HRTF datasets or external SOFA files.

DIRECT mode maps ambisonics to an internal spherical head grid without exposing a named speaker layout. Virtual field mode samples ambisonics through a selected virtual field before the head model. The field path is useful for matching the visual language of the speaker decoder; it is not required for binaural decoding.

Head Profiles

Medium head: default synthetic profile.
Small head and Large head: change the broad shadow/pinna profile without implying a measured listener.
EAR: independent ear-width control in centimeters. This affects interaural delay and the GUI head/ear spacing separately from the selected head profile.

Modes

Binaural is intended for headphones. Transaural starts with the same stereo ear signal, then applies a crosstalk-cancellation stage for loudspeaker playback. Transaural mode depends strongly on speaker angle, listener position, and room acoustics.

The transaural stage uses delayed and filtered opposite-channel cancellation, optional matrix-inverse-style compensation, low-frequency protection, stereo preserve, and output safety gain.

Controls

Control	Meaning
ORD	Ambisonic order, from `1OA` to `7OA`.
DEC	Decoder path. `DIRECT` uses an internal spherical head grid; `Virtual field` uses the selected field layout.
FIELD	Virtual field layout, active when `DEC` is set to `Virtual field`.
WGT / AGN	Ambisonic order weighting and output autogain.
HEAD	Synthetic head profile in the `BINAURAL` toolbox.
MODE	Binaural or transaural.
YAW / PIT	Listening direction.
WID / PIN / EAR	Stereo width, pinna influence, and ear-width spacing for the synthetic head model.
ROOM / XTC / XMOD / SPK / LOW / KEEP	Room/diffuse blend, transaural cancellation amount, mode, speaker half-angle, low-frequency protection, and stereo preserve.
OUT	Final output gain.

REAPER Routing

This plugin exposes a true stereo output bus. On wide REAPER tracks, higher track channels may still pass around a true stereo CLAP plugin unless the host pin connector clears them. If a following meter shows channels above 2, open the plugin pin connector and enable Zero out unmapped output channels.

Use Ambi Decoder Stereo for loudspeaker-style stereo pickup models. Use this Decoder Head when the monitoring target is headphones or a transaural loudspeaker setup.