Finally, an Affordable Ambisonic Microphone

Long, long ago, in a city far, far away I was a college student. I was studying media arts, and somewhere along the line decided to do a paper on an emerging new approach to recording called Ambisonics. This is a most elegant approach to recording conceived by Michael Gerzon, a brilliant, English mathematician. Beyond simply the theoretical, Gerzon developed a microphone in support of his idea, which became the Soundfield Microphone.

How I lusted after a Soundfield microphone, and the four-channel recorder necessary to make field recordings. Manufactured in England by Calrec, the Soundfield microphone cost upwards of $10K on its own. As a not quite starving, but certainly hungry student, this was far beyond my reach.

I consoled myself with the knowledge that the world was a better place for the mere existence of such tools. I take as proof of this assertion The Trinity Session CD by Cowboy Junkies. This hauntingly beautiful album was recorded inside Toronto‘s Church of the Holy Trinity on November 27, 1987. It was a live-to-tape recording, with the band clustered around a single Soundfield microphone.

I’ve never lost my admiration for Ambisonics as an approach to capturing an acoustic event, but I’ve never been able to justify the cost of acquiring suitable equipment. I was tempted by Core Sound’s Tetramic some years ago. More recently, I’ve used AmbiExplorer for Android to playback surround encoded files.

All the above is preface, for this week I pre-ordered a new Ambisonic microphone being offered by Twirling. The Twirling 720 Lite (pictured above) is billed as “The world’s first VR audio microphone for your mobile phone.” Currently available for pre-order for just $89, I simply couldn’t resist.

At that price the microphone capsules are, let’s just say, cost-effective. Probably not the quietest, or flattest. Nonetheless, it’s a bone fide tetrahedral microphone array conveniently adapted to be a generic USB audio device. Connect to a smart phone or computer and make real, first-order Ambisonic surround sound recordings.

The resulting recordings are in what is known as “A-format.” This is comprised of four signals that collectively encode the entire sphere around the microphone. They can be manipulated on playback to make the sound stage move. It’s effectively pan, tilt & zoom for audio.

They have a YouTube clip that shows this in action. To hear the effect you need to be wearing headphones.

At this price the microphone alone is a bargain, but Twirling is also providing software for manipulating the recordings.

Here’s another example of Ambisonics as implemented in YouTube’s spherical VR experience. As the musicians play you can rotate the view and the soundstage track what you see.

The effect is more obvious with instruments that are higher in pitch. It’s especially effective as they softly work the gong. I can rotate left-to-right and hear the ringing of the gong clearly repositioned to reflect the changing view.

I look forward to tinkering with this new microphone. It’ll give me reason to start looking for interesting musical events to record. Beyond music, imagine Cluecon 2018, presented in surround sound, with questions from the audience that sound like they come from beside or behind you. Perfectly conveyed to remote participants via 4-channel Opus-encoded audio.

It’s interesting that almost 50 years after its introduction, Ambisonics is finally starting to see more widespread use. New, more affordable tools are being offered, driven by the push for rational surround-sound in support of gaming and virtual reality.