O3A Upmixers

The O3A Upmixers library is a set of plugins that can be used to convert mixes in various other standard formats into 2D or 3D O3A.

The plugins are:

  • O3A Upmixer - 5.1
  • O3A Upmixer - 6.1
  • O3A Upmixer - 7.1
  • O3A Upmixer - 7.1.2 (Dolby Atmos)
  • O3A Upmixers - Auro-3D 9.1, 10.1, 11.1 and 13.1
  • O3A Upmixers - IMAX 5.0, 6.0 and 12.0
  • O3A Upmixer - 22.2
  • O3A Upmixer - Quad
  • O3A Upmixer - Cube
  • O3A Upmixer - Stereo
  • O3A Upmixer - Coincident Microphone
  • O3A Injector - First Order
  • O3A Injector - N3D
  • O3A Mono Ambience
  • O3A Stereo Ambience

These are higher order ambisonic (HOA) VST2 and AAX plugins for macOS (10.7+) or Windows (Win7+) running on 32bit/64bit Intel. They can be hosted in some Digital Audio Workstations (DAWs) that can handle tracks with at least 16 channels. Options include Reaper, Pro Tools Ultimate, Pyramix and Max/MSP. Not all plugins are supported in AAX.

These plugins use the SN3D ambisonic convention, at third order.

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O3A Upmixers


Why Upmix?

There are lots of good reasons to upmix. For instance, you might want to add some stereo or 5.1 recordings into a 3D O3A mix.

O3A Upmixer Diagram

You might also want to edit an existing mix. For instance, you can take a 5.1 mix, upmix it to O3A, rotate it and add some O3A reverb, and then decode it back to 5.1.

O3A Upmixer - 5.1 Screenshot

Multichannel upmixers are provided for quad, cube, 5.1, 6.1, 7.1, 7.1.2, Auro-3D and 22.2.

How Does This Work?

The multichannel upmixers support two modes. In "Virtual" mode, each channel is panned into place, like a "virtual speaker". Alternatively, "Inferred" mode uses a patented technique to help fill in the gaps between speakers.

Either way, we use passive processing techniques, so we don't mess with the character of the sound. You won't hear any DFT processing artefacts.

Stereo Upmixing and Ambience

The main stereo upmixer "O3A Upmixer - Stereo" presents material as a "stage" that can be moved around the scene. It allows you to control the stereo width smoothly, so you can swing the stereo image out from a single point to ultra-wide.

O3A Upmixer - Stereo

If you don't want a strongly localised stereo image, you might want to try the "O3A Stereo Ambience" plugin. This spreads the left and right channels out over a whole region, so a complete 3D ambience can be generated from just a stereo input. This is often useful in Virtual Reality to handle music or other non-diegetic material. There is also a mono version of this plugin, with a disconcerting "Movement" option.

Other Tools

Some more plugins are included, to help introduce other material into 3D O3A mixes. There is support for another ambisonic format (HOA using N3D in ACN order), for 2D coincident microphone systems like the Zoom H2 or Double M/S, and a processor to help when injecting first order material. Obviously, you can also use panners, for instance from the O3A Core!

Plugin List

O3A Upmixer - 5.1

I/O: 6 in, 16 out

This plugin converts 5.1 surround into a 2D O3A mix.

O3A Upmixers
O3A Upmixer - 6.1

I/O: 7 in, 16 out

This plugin converts 6.1 surround into a 2D O3A mix.

O3A Upmixers
O3A Upmixer - 7.1

I/O: 8 in, 16 out

This plugin converts 7.1 surround into a 2D O3A mix.

O3A Upmixers
O3A Upmixer - 7.1.2 (Dolby Atmos)

I/O: 10 in, 16 out

This plugin converts 7.1.2 surround into a 3D O3A mix.

O3A Upmixers
O3A Upmixers - Auro-3D 9.1, 10.1, 11.1, 13.1

I/O: 10, 11, 12 or 14 in, 16 out
AAX: only 9.1 supported, mapped to 7.1.2

This plugin converts Auro-3D surround into a 3D O3A mix.

Note the number of channels that need to be input to this plugin. The plugin does not unpack compressed Auro-3D audio.

O3A Upmixers
O3A Upmixers - IMAX 5.0, 6.0, 12.0

I/O: 5, 6 or 12 in, 16 out
AAX: IMAX 12.0 is not supported. IMAX 6.0 is mapped to conventional 6.0

This plugin converts IMAX surround into a 3D O3A mix.

O3A Upmixers
O3A Upmixer - 22.2

I/O: 24 in, 16 out
AAX: not supported

This plugin converts Hamasaki 22.2 surround into a 3D O3A mix.

Note that this plugin needs even more channels than usual.

O3A Upmixers
O3A Upmixer - Quad

I/O: 4 in, 16 out

This plugin converts quad surround into a 2D O3A mix.

O3A Upmixers
O3A Upmixer - Cube

I/O: 8 in, 16 out
AAX: input mapped to 7.1

This plugin converts audio targeting a cube of speakers into a 3D O3A mix.

O3A Upmixers
O3A Upmixer - Stereo

I/O: 2 in, 16 out

This plugins spreads a stereo image dynamically over a region of space.

O3A Upmixers
O3A Upmixer - Coincident Microphone

I/O: 4 in, 16 out
AAX: input mapped to quad

This plugin processes recordings from 2D coincident microphone systems with simple polar patterns, such as the Zoom H2 or Milab SRND 360, or Double M/S systems. It converts to first order ambisonics and then to O3A, applying some gentle processing if required.

The results from this plugin are less sharp than from proper O3A panning, and these systems do not record height information. However, this can be a good way to add ambient field recordings into a O3A mix.

O3A Upmixers
O3A Injector - First Order

I/O: 4 in, 16 out

This plugin applies some gentle processing to first order ambisonic material that sometimes helps when injecting it into a third order O3A mix.

O3A Upmixers
O3A Injector - N3D

I/O: 16 in, 16 out

This plugin converts Higher Order Ambisonic (HOA) material using the N3D convention (in ACN) to the SN3D convention used by O3A.

O3A Upmixers
O3A Mono Ambience

I/O: 1 in, 16 out

This plugin spreads a mono signal in all directions.

O3A Upmixers
O3A Stereo Ambience

I/O: 2 in, 16 out

This plugin spreads a stereo signal in all directions, or over regions on the left and right.

O3A Upmixers

Tech Requirements

O3A Plugin Technical Requirements

Please check that everything is okay here before purchasing software.

Operating System

Supported versions of Microsoft Windows are Windows 7, Windows 8 and Windows 10. Supported versions of Apple macOS X are 10.7 or later, Intel only. The VST plugins are available in 32bit or 64bit forms on both platforms (packaged as a Universal Binary on macOS). The AAX plugins are 64bit only.

VST Host

The VST plugins require a VST 2 host with shell plugin support.

These plugins do not work with all VST 2 hosts. One reason for this is that the O3A plugins need large numbers of channels on their input or output busses. Check the individual plugins for the channel counts they need, but all of the O3A plugins need at least 16 channels on each track, and a few need more. Also note that not all VST 2 hosts can use shell plugins. In particular, at the time of writing shell plugins are not supported in Nuendo or Cubase.

AAX Host

The AAX plugins require Pro Tools Ultimate, or Pro Tools HD v12.8.2 or later.

Due to channel and stem restrictions, not all plugins are supported in AAX. Please see the documentation for details.

PC Hardware

Please check your PC meets the following requirements:

  • Intel Pentium D CPU or better.
  • 200MB of free disk space.
  • Internal network card.

Internet Connection Required

These plugins require an Internet Connection for license activation and verification. We don't really like this, but we can't think of a better way to discourage piracy! Please don't hack our code, it's taken a lot of effort to get it this far...

Successful license verification isn't required every time you use the software, but it is needed during installation and needs to succeed once every couple of weeks to keep the license fresh.

The license can be "revoked" to remove it from one machine so it can be moved on to another. You should also do this if you're updating your system in case the machine appears to have changed identity.


You'll need administrator permissions while installing on Windows. The software won't install properly using a "restricted" account.