A-Format Stream

A-Format sources allow to input in HOLOPHONIX the direct output stream of a 1st order Ambisonics microphone. Presets corresponding to the following microphones are available:

  • Sennheiser Ambeo,
  • SoundField ST250, ST450 and SPS200,
  • RØDE NT-SF1,
  • DPA-4
  • Oktava MK-4012.

The A-Format stream is the signal coming out directly of the microphone capsules. If you have allready transcoded that to a standard ambisonics stream using the manufacturer's software, use a B-Format stream source.

The A-Format stream will be automatically decoded to your loudspeaker layout by the chosen HOA bus.

Because it is an 'audio stream' type of source (that has no spatial position), it is not associated with an object in the 3D VENUE view.


A-Format sources can only be assigned to HOA 3D buses.


For Higher Order microphones (i.e. with more than four microphone capsules), use the dedicated type of sources (Eigenmike®, Zylia®, and HOA Stream).

Audio Parameters#

All parameters are similar for all sources except for the parameters below. Check the source audio parameters section.


After the A-Format source is decoded, the Reverb level sends the W omnidirectional channel of the Ambisonic stream to the reverberation bus. There is no early and cluster simulation for Ambisonic sources.

A-Format Parameters#

Mic Type#

Choose the model corresponding to you microphone within the available presets. If your microphone is not in the list, use the manufacturer or a generic B-Format transcoder, and a B-Format source. You can also contact our user support to create the preset corresponding to your 1st order ambisonics microphone.

Mic Radius#

The radius of the microphone is set automatically when selecting a microphone model. However, this parameter can be adjusted manually if necessary. The radius cannot be changed when filtering is off.


The Filtering option activates high-frequency filters to compensate for the non-coincidence of the microphone capsules, and enhance the Ambisonic signal.


The orientation of the A-Format stream can be adjusted with Yaw, Pitch, Roll, to rotate the entire audio scene. See rotation angles.