Ambisonics isn’t new. It’s been around since the 70s but for a few reasons it was a technology, which was before its time. Thankfully the world has caught up with Ambisonics and most of the barriers, which prevented it thriving the first time around have largely fallen away. One of the most significant of these was the complexity and expense of the equipment necessary to decode Ambisonics. Now replaced by software, much of which is free, Ambisonics is experiencing a renaissance largely due to interest in VR but even if you aren’t involved in anything to do with VR, Ambisonics has benefits to offer anyone open to new ways of working.
What Is Ambisonics?
Ambisonics is a method for recording, mixing and playing back three-dimensional 360-degree audio and while it can be used without, the most common way of capturing audio for Ambisonic work is using a specialist mic with a tetrahedral array. For decades the only way to do this was using a Soundfield mic but with the resurgence of interest in this way of working, several new players have launched Ambisonics mics. The one with which I have experienced is the Sennheiser Ambeo mic.
The Sennheiser Ambeo Mic
The mic is compact, small enough to fit into a Rycote windjammer and because the orientation of the mic can be configured in the free Ambeo A format to B format converter plug-in it can be stand mounted, used as an end fire mic or even hung from a cable upside down. It outputs on a multi-pin connector and comes with a breakout cable which outputs to four standard 3 pin XLRs.
When I used the mic I found it quiet and very neutral with a sweet top end. I’d say it sounded good off-axis but there isn’t an off axis with a mic like this. The interesting thing about the current crop of Ambisonics mics is that whereas there used to be one choice if you wanted an Ambisonics mic - you bought a Soundfield, and a Soundfield mic, while an excellent microphone was an expensive item, but now there is a choice of products the cheapest of which, the Zoom H3-VR is the same price as a pair of budget condensers and is a recorder too! Then there is the new Soundfield, which since its acquisition by Rode is now the RØDE NT-SF1.
The Sennheiser Ambeo hits the sweet spot being a thoroughly professional piece of kit but priced to be accessible, it’s not cheap but it is reasonably priced at around £1300.
What Is Ambeo?
Ambeo is Sennheiser’s program and trademark for immersive 3D audio, designed to create sound experiences with a high emotional impact because Ambeo operates with a height elevation that gives audio its natural three-dimensional character. This is why you often hear this described as “3D audio”. The program covers products and technologies for the entire audio signal chain, from capture to mixing and processing to reproduction. An example of another Ambeo product is the Ambeo Smart Headset, designed to capture binaural recordings with iOS devices.
What Are A and B Format?
When talking about Ambisonics - Second and third order Ambisonics use more channels for greater accuracy in localisation, whereas first order ambisonics - A format and B format are both four channel audio streams which capture a full 360 degree spherical soundfield. The difference is that A format is the unprocessed output from the four capsules in the tetrahedral mic array in a first order Ambisonic mic like the Sennheiser Ambeo. B format is still a four channel stream but has been processed into W, X, Y and Z components, equivalent to Omni, left-right, front-back and up-down.
6 Reasons To Get Into Ambisonics
Future Proof Capture Format - It doesn’t matter what new formats emerge in the future, as long as the original A or B format files are available an Ambisonics recording will be able to be rendered to any output format. Learn more about this in our article How To Record, Edit and Publish An Ambisonics Sound Effects Library.
From one format it is possible to output sound effects to suit both surround formats like 5.1 and 7.1 but immersive formats like Dolby Atmos because the Ambisonics format has for 360 coverage as well as height information.
Ambisonics is 360 degree spherical, that means it captures height information, unlike conventional surround arrays.
Ambisonics is old technology which now has become useful to a mass audience because the world has caught up with it. VR headsets like Oculus Rift and Google Cardboard and head tracking headphones like Waves NX or the EDtracker make Ambisonics relevant and accessible to ordinary consumers on consumer budgets.
It’s the only choice for Immersive 360/VR Video. B format is an accepted format for exchange of audio in a VR workflow. Sound effects collections come in B format and can be processed by Rode Soundfield plug-in.
Production Expert Contributor Tom Lowe wrote a piece detailing his production decisions when compiling his “London Ambisonics” sound effects library.
“I did consider making stereo and 5.1 versions for ease-of-use, but considered that if I had bought the library, I would want the flexibility to choose how to use the sounds, rather than have decisions baked in for me.
In B-format software such as Harpex-X, or the free Rode Soundfield plug-in (which has replaced the older SurroundZone plug-in now that Rode own the Soundfield product range) the user can also decide which mode of stereo sound they’d like to decode to, such as AB, XY, spaced-omni etc. so again thought it would be best to leave this to the end users to decide.”
Binaural or stereo can sound good but are “static”. When wearing headphones the sound field moves with your head. If you capture 360 spherical you can choose your viewpoint “post capture”. Ambisonics can be processed to give a “Dynamic Binaural” output where the audio tracks the viewpoint of the listener for a genuinely immersive experience.
If you are someone who records music in stereo and thinks that, interesting as it might be this Ambisonics thing isn’t relevant to you, you might be missing out. Anyone who has seen virtual mic systems like the Townsend Sphere will have seen that, as well as the mic modelling (which is the principal feature) the mic also offers control over the polar pattern post record. The ability to do this, in stereo through 360 degrees opens up some interesting possibilities. For example what if you were to capture a group of three backing singers arranged around an Ambisonics mic in a single pass. Post record you could use a mono hypercardioid pattern aimed at each singer in turn and the three bounces would have excellent rejection of the other two singers and any spill would be perfectly phase coherent because they were all captured by the same mic. You could try something similar on a drum kit or a string quartet, there are so many possibilities.
Ambisonics is still unfamiliar to many but it’s not difficult and it’s available to anyone with Pro Tools Ultimate, check out our article Ambisonics In Pro Tools - Want To Learn How To Get Started? We Have 4 Avid Tutorials To Help You With VR Immersive Mixing for more on how to use Ambisonics in Pro Tools Ultimate. if you don’t have Pro Tools Ultimate then Reaper and some free plug-ins is all you need apart from a mic.