Music & Tech & Posts by José Luis Miralles

#2 – 360AJ – AMBISONICS to DAW (Logic & Ableton) and audio track types

Hi again! I’m back here after the first episode in this public journey about learning how works 360 audio.

After first attemp in recording with the Zoom H3-VR, it is time to be serious and try to import the files to my regular DAW for music post-production: Logic Pro.

We can simply drag and drop the file in a new track? We need to do some special adjustements prior to that? Let’s see!

First we must understand the audio track types in our DAWs.

LOGIC PRO X

First, make sure you have “surround” enabled in advanced settings (in Logic pro preferences).

The different audio tracks you can create in LPX are:

  • In1: A (singel circle) mono channel (from entry 1 of your input device)
  • In1-2: (venn diagram) A stereo channel (from entries 1&2)
  • Left (two circles, left full): only playing the left channel
  • Right (two circles, right full): only playing the right channel
  • Surround (4 dots, and 1 dot – from 5.1)

To change between this all kind of channels, you need to hold click in the relative icon of each channel. If you only make a single click you are toggling between mono and stereo.

And what about the outputs?

  • If we have a Mono entry:
    • Mono output. We don’t have any pan controls.
    • Stereo out: We can choose between Pan and Binaural Pan
    • Surround: We only have Surround Panner
  • If we have a Stereo entry (irrespective from listening both channels or right or left) or Surround entry
    • No mono output
    • Stereo out: We can choose between Pan, Stereo Balance, Binaural Pan
    • Surround: We only have again Surround Panner (except if we have a surround input, thus we have a Surround Balancer)

From left to right: Pan, Stereo Pan, Bianural Pan, Surround Balancer. If we double-click in each pan control we can gain acces to more detailed controls only in Binaular Pan and Surround Panner:

A bit about channels

A mono file has only 1 channel. A stereo file has two channels (commonly Left & Right). But a surround file?

A surround file can have a different combination of channels. Let’s talk today only about the most common configurations, the 5.0 or 5.1 specifications. The 5.0 means 5 speakers:

  • FL – Front Left – placed in an angle of 60º
  • FR – Front Right – 60º
  • FC – Front Center – in front of the listener
  • SL – Surround Left – 100º-120º
  • SR – Surround Right – 100º-120º

And the 1 from 5.1, only adds a subwoofer, which position is not very important. Commonly called LFE: Low Frequency Effects.

Typically a surround file, mostly recorded with a mic array like a Decca tree, has only 5 channels, the low frequency spectrum information is not recorded by a dedicated mic. More about surround configurations.

Ambisonics, are similar to sourround files, but one of the main diferences is this:

In any surround system we are speaking about speakers 😉 , but ambisonics is speaker agnostic, so it doesn’t matter wich combination of speakers or output channels we have.

The ambisonics formats also can have different kind of “channels”, but here we are speaking about “orders” more than channels. These orders are the number of audio channels within the file.

  • 1st order: has 4 channels of audio
  • 2nd order: has 9 channels of audio.

So, what happens if we try to import our ambisonics files from the H3-VR? We get 4 channels. The name of the 4 capsules of the H3 are:

  • BRU: Back Right Up
  • FLU: Front Left Up
  • FRD: Front Right Down
  • BLD: Back Left Down

The math background beyond the ambisonics technolgy is called Spherical Armonics (I think we will digg deeper in other posts about that) and the signals in this theory are called: W (as omnidirectional) and X,Y and Z. In ambisonics each individual speaker recieves a combination of the above signals corresponding to each position of the speakers.

So, besides this not-yet-fully-explained math background, we can deduce that for playing an ambisonics file we need something to do one of the following scenarios:

  • Decode the signal into another “listerner-static” format: like mono, stereo or even surround.
  • Have a binaural processor to decode the signal in, obviously, binaural.
    • Being physically static and playing with rotations and positions with the mouse or other controller.
    • With a head tracker or gyroscope (maybe inside a VR headset) in order to tell the processor wich is our relative position and moviments and accomplish the calculations.

I think Logic Pro it doesn’t have a native decoder nowadays, so we need to search into the plug-ins domain (in future posts we will take care of that).

We can conclude is not as easy as drag and drop to open correctly an ambisonic file in Logic Pro. Let’s take a look with other DAWs I use.

ABLETON LIVE

With Ableton Live, things seems less complicated. We need to download some extras from their Max4Live devices.

In a native way we have a very simple Surround Panner (without LFE channel) an no free position of speakers (only some presets):

But we can use the Envelop tools for Live for unlocking more spatial audio. This tool is mandatory to open an ambisonics file, or output to ambisonics! (wow, Logic Pro doesn’t have that).

You have all the documentation of the device here: https://github.com/EnvelopSound/EnvelopForLive/wiki

In order to open our Ambisonics B file in Ableton we need two things from the Envelop tools suite:

  • The E4L Master Bus device in a dedicated audio track.
  • The B-format Sampler device in an audio track, so we can load our AmbiX or FuMa audio file.

The Envelope Tools suite for Ableton live has a lot of other effects and possibilities (as always, work for another post).

Todays step in this journey was only about trying to open (and talk a little about audio channels) a recording of a Zoom H3-VR.

Next post will be about doing the same with Reaper (it seems that is the more capable of work with Ambisonics files).

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