Soyuz: 013A Ambisonic Mic

I’ve loved everything Soyuz has made so far and own many of their mics, but ambisonics seemed like an odd direction for them. When Soyuz announced the 013A Ambisonic Mic, I began doing more research on the topic. From the little I knew of ambisonics, it was a bit of a complicated process with a lot of unfamiliar jargon. I also wasn’t convinced it would be the kind of thing that would be useful to me as a producer/engineer who focused exclusively on music. I worked in the San Francisco Bay Area for a while, with many people from companies like Pixar Animation Studios and Skywalker Ranch. I've dipped my toes into that world, and learned that some engineers love ambisonic mics for use in film, games, and even classical music. I quickly discovered that although it’s still a bit of a niche area in the music recording world, ambisonics can offer a world of possibilities, especially with immersive formats such as Dolby Atmos.

Ambisonics has been around since the '70s, and captures a complete 360-degree recording that can be manipulated in the mix. Though processing and decoding this technology is based on an older format, with modern computers and DSP solutions the sky really is the limit on how you can edit an ambisonic recording in post. You can turn the signal into essentially a single-channel mono microphone in whatever polar pattern you like, take it to stereo as a virtual stereo pair of microphones, point it in any direction inside the virtual sphere, or spread it all the way out to larger immersive configurations. The best way I’ve heard ambisonics described so far is “speaker agnostic,” and it’s the most flexible recording format I’ve come across.

So, what is the 013A Ambisonic Mic, and how do I use it? It is four channels of Soyuz 013 FET microphone [Tape Op #139] capsules and transformer circuitry compiled into an ambisonics array, housed in an 023 Bomblet [#140] style body. I’m honestly not sure how they made it all fit in there, but they did. The 013A is considered a first-order ambisonic microphone, meaning it has four channels. This is generally considered the minimum starting point for ambisonics to work properly, though it can be achieved with just three channels. There are variously increasing “orders” of ambisonics; you’ll find some specialized mics going from third-order (16 channels) all the way to some insane options with over 84 channels. Most DAWs will let you process up to higher-order ambisonics, but often require software upgrades to reach a high channel count.

A first-order ambisonics DAW setup requires that you record the microphone's four cardioid channels in a specific array, referred to as A-Format. Soyuz includes a custom color-coded XLR cable that makes it easy to ensure you’re ordering your four channels accurately. When you get that right, you’ll end up with an A-Format file. This is when spatial audio software company Audio Brewers gets involved. There's a reason Soyuz decided to partner with Audio Brewers: Although it all comes down to math (more or less) to decode an ambisonic signal correctly, I found that not all software and plug-ins built for this purpose are created equal. I tried the options from the largest plug-in company in the world (they’ll come up as one of the first results if you start googling around), and the results were beyond disappointing. Audio Brewers' Alejandro Cabrera is extremely knowledgeable about ambisonics, and I’ve happily settled on this software option for my decoding.

Now, you’ll need to take that four-channel A-Format file and transcode it correctly. Every ambisonic microphone has to be uniquely transcoded. Audio Brewers has taken the 013A, measured the physical configuration and distance between the four capsules, and made a proprietary transcoder plug-in specifically for Soyuz. You must "tell" the transcoder plug-in how you physically oriented the microphone for your recording. At that point, the transcoder plug-in will take that A-Format file and accurately transcode it to B-Format, essential for using different ambisonic plug-ins and software. It does all of the required math for that specific microphone so that it can be decoded and manipulated correctly by any software you choose to use. That transcoding process is a bit processor-heavy, so Audio Brewers has included a Monitor option that reduces the quality of the transcoding sufficiently for low latency monitoring of a decoded ambisonic signal in real-time.

After that signal is transcoded correctly, a decoder plug-in is used to orient and manipulate your ambisonic recording in its intended delivery format. Many software options are available for this, but I would again recommend sticking with the included Audio Brewers decoder. Decoder options for orienting the transcoded channels can be anywhere from mono, stereo, or any conceivable surround sound format. Again, because this technology is “speaker agnostic,” you’ll be able to accurately translate this into whatever crazy antics the future throws at you. Dolby Atmos is an obvious choice right now, but the important part is to remember that ambisonics doesn’t care. It’s truly future-proof, and that’s one of the many beautiful things about recording in this format. If you ultimately want to stick with stereo content for an ambisonic recording, it’s easy to convert and follow that signal with any of your normal stereo format plug-ins. This may seem complicated at first, but it really is as simple as throwing up two plug-ins in the correct order. The beauty of ambisonics is that you can make this all as complicated or simple as you like.

What makes the 013A unique, however, is that it’s designed to be used as more of a creative instrument than a sterile and scientific capture device. Soyuz's 013 line is hands down one of the most musical-sounding microphones I’ve used, and by far my favorite smaller-diaphragm capsule. I’ve also had a chance to use the handful of other common four-channel ambisonic mics out there. Although they all offer similar versatility and astounding imaging aspects, I would categorize them very much on the clinical side of the sound spectrum. The 013A is made for musicians and creative people, and was the option I easily settled on for music making; the comparisons weren’t even close.

The sound of the 013A will be very familiar to you if you’ve used a 013 FET before. Very similar midrange and color, but with a more open top end and a slightly tamed proximity effect. Although Soyuz has not changed anything in the circuit or capsules, I suspect the sound differences are related to the ambisonic decoding process and the effect of the off-axis response of all the capsules in relation to the ambisonic array. Versatility is the key here, though, as you can take the ambisonic signal and decode it down to mono in different polar patterns to take advantage of the tamed proximity effect and open top end. Or you can simply point one of the capsules directly at your source and record one channel as a mono mic. You’ll also save a lot of time and frustration on sources like drum overheads as you can place the mic where you want it, decode it to stereo, and then balance your image with the decoder plug-in from your control room. No more going back and forth tweaking mic placement to get your kick and snare centered in the overheads!

I hope this inspires you to give ambisonics a try. I’ve done an over hour-long video detailing all of this on the MillSounds YouTube page, where you can download full ambisonic session files of a whole song I recorded with the 013A. I think once you begin to understand this technology the future will make a lot more sense, and if you’re like me, your brain will explode with a whole new world of creative possibilities.