Explorers of Ambisonics – John Leonard


When I first began considering writing about Ambisonic field recordings, my thoughts immediately turned to John Leonard.

Readers may remember John from his interview in the “A Month of Field Recordists” series. In addition to his carefully recorded sound effects, John Leonard has been a pioneer in Ambisonic field recordings. He has followed the evolution of the format and has produced some of its best field recordings. While many people have begun recently using Ambisonic sound effects for 3D and VR platforms, John has vast experience using them differently: as soundtracks for his award-winning theatre sound productions.

I asked John if he would be interested in sharing his perspective on Ambisonic sound recordings with us. I was delighted when he agreed. What emerged was a fascinating look at John’s career, and a comprehensive description of the history and evolution of the Ambisonic format and its tools.

Creative Field Recording: Can you share with readers how you first discovered the Ambisonic technique?

John Leonard: In my early days in theatre back in the 1970s, I used sound effects in surround a lot: obviously, just mono or stereo sounds routed to speakers around the auditorium, but I could see how effective it could be and started looking at different ways of achieving surround. The SQ/QS etc. surround systems for home surround were just being introduced but were not impressive and certainly not any use for large-scale reproduction. I had some success with the Hafler hack, where you derive a surround signal by collecting the out of phase information from stereo recordings and route that to surround speakers and that gave some very interesting results, with the original vinyl recording of Jimi Hendrix’s Voodoo Child (Slight Return) from Electric Ladyland album producing some pretty whizzy effects. But then I read an article about the Soundfield microphone in the (now defunct) Studio Sound magazine which got me rather more excited and I got to meet Michael Gerzon, (the main driving force behind Ambisonics and the Soundfield Microphone with Peter Fellgett and Peter Craven) and eventually wangled an invite to the Calrec premises to hear a demonstration of a recording made using a Soundfield at The Royal Albert Hall in London. That was in 1978, I think, and I was an immediate convert, not just in terms of the ‘being there’ experience, but also with the way that you could alter the perspective and angle of the recording after the event. The system wasn’t exactly portable and it was way out of the price range for the theatre company I was working for, but it sparked an idea about the possibility of positioning mono sounds in a 360º sound field, which I started to pursue shortly afterwards, although politics and money rather stymied that project half way through.

ST450 Boat Recording Session

I remained interested in Ambisonics and kept up with any developments, including that of the Audio & Design Recording’s Pan-Rotate unit, which achieved pretty much what I had envisaged a few years earlier, but which we still couldn’t afford, theatre sound not being the blessed with enormous resources. When the ST250, the first truly portable Soundfield microphone was announced, in the late 1980s, I put down a deposit and after a slightly odd beginning, during which Calrec sold their Soundfield microphone business to AMS, I duly acquired microphone number 007. Admittedly, that one had its problems, occasionally turning into a very expensive noise generator and after a bit of back and forth I eventually ended up with number 047, but that served me well for over twenty years and is still going strong in the hands of another user, since I upgraded to an ST450 a few years ago.

CFR: What inspired you pursue Ambisonic recordings? You have been capturing Ambisonic field recordings across the evolution of the format. Why is it about this format that continues to intrigue you?

JL: Initially, you needed specialist hardware for transcoding B-Format recordings to useful speaker outputs and I did my initial theatre playback tests using Richmond Sound Design’s AudioBox system, which has extensive matrixing facilities built in and with which we could construct a fairly decent full surround-with-height set up. Playing back ambience tracks recorded in Manhattan gave a much greater sense of realism than by simply routing stereo effects to the surround speakers, even with first order B-Format recordings that produce a relatively small sweet spot, so that was a good reason to carry on recording effects using a Soundfield system.

SurroundZone2 Software

Then software developments started to arrive, both commercial, with the original Soundfield SurroundZone and public domain material from assorted sources like Bruce Wiggins at Derby University in the UK and Daniel Courville’s suite of tools, which made encoding and decoding much simpler using plug-ins for various DAWs.

Lately, Svein Berge’s Harpex decoder does some very clever stuff indeed, as does Richard Furse’s collection of tools at Blue Ripple Sound although these are aimed pretty squarely at higher end pro users.

But it’s the ability to do so much work after the event that keeps me coming back to Ambisonics, even if the end result is mono, stereo, 5.1, 10.2 or full 360º surround. It’s pretty much a future-proof format, plus it’s not proprietary, which is a huge plus.

John also pointed me towards a free channel converter from Noisemakers called Ambi-Converter.

CFR: What was the first Ambisonic sound effect you captured? What was your reaction to the final sound, after recording with “conventional” stereo techniques?

Recording a Spitfire with ST250 TetraMic & ULN-8

JL: I was working on a play that started with the sound of a light aircraft hedgehopping and then crashing and a colleague knew a farmer with a light plane who was willing to do some flying for the cost of the aviation fuel. We’d had the full version of the Metric Halo 2882 software and we set up with a PowerBook G3 in the back of my estate car and my colleague got to ride shotgun in the plane with a DAT machine to get some internal recordings. The pilot did a whole set of fly-pasts at very low level, all of which I recorded with the ST250 direct to the Mac, using the Metric Halo’s Record Panel. All very quick and very simple and, once we’d added the sounds of the crash, extremely effective: in fact, so much so, that the director decided that it was all a bit too much and we had to scale it all back down, although the low-level fly-by remained as an extremely powerful opening effect. Those original recordings are trapped somewhere in a set of backup CDs that one day I’ll find a way to restore: that’s a lesson to learned – always make more than one back-up and preferably not using some proprietary software that’s going to disappear, leaving you with a pile of junk.

After that, and with the ability to record on location just by battery power, I pretty much recorded everything that I needed in B-Format, whenever possible.

CFR: What Ambisonic equipment have you tried? Why do you prefer the gear you are using now?

ST250 and 2882 at the Beach

JL: Well, initially, as there were no truly portable four-track machines, I used the ST250 as a superb stereo microphone with remote pattern control, which I could also use as a truly coincident mid-side set-up, giving me a degree of control when I got back home from location recording and many of the effects in my library were captured that way. On a visit to New York, I travelled upstate to meet the guys from Metric Halo and mentioned to B.J. & Joe Buchalter that I was interested in an interface for a laptop that would allow me run a fully portable multi-track system. They were in the process of designing the 2882, which could be powered by Firewire or by a 12v battery and that’s what I eventually ended up testing and buying and I still use Metric Halo ULN-8s today for my studio and indoor music recording.

Although it was an extremely powerful recording set-up, it was still a bit unwieldy to take the Mac laptop, the 2882 and the ST250 to some of the more remote places that I went to record and I experimented with various low-cost multi-channel digital recorders, but eventually decided that I needed a portable machine that had a proven track record and was rugged enough to deal with the toughest location, so I sold some bits and pieces, saved a lot and was lucky to find a second-hand Sound Devices 788T at a reasonable price here in the UK and that’s been the basis of my portable rig since then. I added a 744T as a back-up machine and for times when I need to be even more compact and lightweight.

ST250 and 2882 on a Sailboat

As you know, I started out with a Soundfield ST250, which I loved and which the chaps at Soundfield looked after for me and tweaked from time to time and I really loved it, but it was getting a little too old and fragile for the constant travelling, so I decided that I should investigate alternatives and tried out the Soundfield SPS200-SB, which was an A-Format microphone coupled with a Cinela Zephyx windshield. I tried to like it, but couldn’t get the same results as the ST250 and monitoring was a pain. Then Ken Giles at Soundfield offered me the demo ST450 at a very good price and I sold the ST250 and the SPS200 on to other users. I’m very happy with the ST450: it’s light, compact and outputs at line level, which makes it a very good fit with both the 788 and the 744. I have a DIY battery distribution system that I use with Deben Tracer Lithium-Polymer batteries that keeps the weight down and still gives me many hours of recording time. Wind protection and shock mount are from Rycote, naturally: I’m waiting for them to let me know when they’ve got a version of the Cyclone windshield available for the ST450, which I hope will be soon.

Car Boot with CoreSound TetraMic

I also acquired a CoreSound TetraMic, which I sometime use for indoor work where I need a more discreet option: it needs a really low-noise pre-amp to shine, but in the right circumstances it can give truly excellent results. I did find that it’s not an ideal mic for outdoor work, mostly because it’s very sensitive to handling noise, but coupled with the Metric Halo ULN-8, it’s turned in some really superb results and been pretty much invisible into the bargain.

I’m going to be able to test a Sennheiser Ambeo microphone in a few weeks and it’ll be interesting to see how that measures up to the TetraMic and the ST450.

And actually, I’ve been impressed by the firmware revision for the Zoom H2n which allows you to record in a form that can be decoded for horizontal-only Ambisonic playback. For such a low-cost device, it does a pretty good job. You can use Matthias Kronlachner’s free ambiX plug-in to do the conversion from the Zoom’s ACN channel sequence to the Furse-Malham version and then use whichever B-Format plug-in you want to go from there.

I use Harpex, SurroundZone2 and Dave McGriffy’s VVAudio.com plug-ins on a regular basis for working with recorded files, and Nuendo as my DAW, for the simple reason that it was handling multichannel files years ago without me having to spend enormous amounts on extra proprietary gear.

CFR: When you first began capturing Ambisonic field recordings, gear was a bit more complex. For example, in the past you have used desktop set ups with a laptop to record. Now it is possible to record without that. What are your thoughts on the evolution of the format?

JL: I’m slightly amused by the way that this forty-year-old system has suddenly become all the rage and somewhat annoyed at some of the claims made in PR puff-pieces about how certain companies seem almost to be claiming that they’ve invented Ambisonics, but it can only lead to more development and, I hope, more recognition for the people who’ve been working quietly away in the background to help people like me make and use surround recordings. Obviously, the driving force behind all of this sudden flurry of interest in Ambisonics is the uptake of Virtual Reality, which is not exactly an area in which I have much interest at the moment, as real reality takes up most of my time, but it’s good to see people finally realising that there’s been a wheel that was invented years ago that doesn’t actually need reinventing. As to the kit, well I think that we’re going to see the Sennheiser Ambeo Microphone/Zoom F8 or F4 combination become the low-cost favourite for many VR recording set-ups and it remains to be seen who else will jump on the bandwagon. The recent transfer of the Soundfield kit manufacturing and distribution to Røde is extremely interesting, and although I’m sad to see a great British microphone business move to the other side of the world, I also think that it couldn’t be in better hands and I look forward to seeing developments there.

Software continues to develop and expand the opportunities to use Ambisonics in many other situations and I’m sure that the move to higher order sources will start to make people more aware of what the future could hold in terms of more precise localisation in larger spaces.

CFR: How do you work with Ambisonics after you record them? Do you decode them to a particular format? Do you prefer to edit or browse them in any particular way?

JL: It depends on what the end use is: most of the time, I regret to say, I’ll decode to stereo for playback in theatres or for inclusion in my effects libraries. I do also decode to 5.1 for theatre playback when there’s an opportunity to use a speaker set-up that works, but very often that’s not the case, either because the theatre doesn’t have the necessary kit, or the architecture doesn’t make it practical.

However, recent developments in the specialist theatre playback software that I use, which is Figure 53’s QLab, along with Rogue Amoeba’s Loopback and Plogue Bidule means that I can use B-Format recordings directly in the theatre, which I’m finding very exciting.

Rogue Amoeba – Loopback

Editing is easy in any DAW that handles multi-channel files, but as I said, I prefer working in Nuendo as it’s been geared up for multi-channel output for many years and I use Soundminer as an effects library, which can now also handle and display multi-channel files and can insert the necessary plug-ins to the monitor chain to give you monitoring possibilities.

CFR: Do you use your Ambisonics in your work in theatre production? How do Ambisonics help portray sound on stage, or for the audience?

JL: I pretty much covered that in previous answers, but it’s worth repeating that when it’s possible to use Ambisonic effects recordings in a properly set up system, I’ve found that the sense of immersion and realism for the audience is much improved and that it’s more readily accepted than straightforward panning of mono or stereo effects. Using Ambisonic playback on stage is much more difficult as speaker positioning tends to rely very much on the set design and the last thing that a director or set designer wants to see is a bunch of loudspeakers intruding onto a beautifully designed stage set. There’s a story about a certain opera house where a full periphonic playback system was installed in its new auditorium specifically at the request of one particular composer. This did not go down well with the director of the opera company who hated the look of these speakers all over his lovely new opera house and he ordered them to be removed, which they were, and as far as I know, the whole, very expensive system was never used in anger.

CFR: What are some common misconceptions about Ambisonic field recordings?

JL: I think that the biggest misconception is that Ambisonic field recording is a one-size-fits-all solution, which really isn’t the case at all. Like any field recording situation, you need the correct tool for the job, as well as realising that the basic rules of field recording still apply. Yes, you can play around with the recording back at the studio, but if you haven’t placed the microphone correctly, the best software in the world isn’t going to get you out of trouble. You also need to consider what you’re recording and whether it might be better recorded in a different way. I have other mic set-ups – M/S pairs and single-point mics from Sennheiser, Neumann and Sony, a DPA 5100 surround microphone, Schoeps DMS sets, DPA 4060 & 4061 discreet pairs and a Telinga Parabolic and I can lay my hands on a Neumann KU-100 dummy head if I want to go binaural. I make the decision about what to use depending entirely on what I’m recording and where I’m going to be doing it. If there’s going to be surround material worth recording, I’ll use the Soundfield, but if it’s not practical, then one of the other set-ups will be used. Sometimes, it’s a purely practical decision; for instance, I recorded under Niagara Falls a few years ago and that would have been an expensive disaster with the Soundfield, whereas the Sennheiser mid/side pair did a pretty good job of coping in a very wet situation.

CFR: Ambisonic recordings have received a lot of attention particularly in the last few years. What do you think about that, and where do you see the format going in the future?

JL: The interest is being driven by the rise in VR and it seems that VR developers have found that it’s relatively simple to convert an Ambisonic recording to a useable binaural signal which can be used with head-tracking, with programs like Ambi Head from the French company Noisemakers so in that respect, there’s a definite future. For large scale cinema reproduction, I think the big guys will prevail with their alternative surround with height systems, principally because most of the infrastructure is already in place. It may well be that they’ll start to work on ways for Ambisonic recordings to be incorporated into the workflow, which would be good. I have to say that my one experience of a commercial surround with height system in a cinema wasn’t exactly thrilling: they seem still to be at the stage of “‘we’ve got this speaker in the roof, let’s put something in it” without particular regard as to what that might be. Very often, I find that’s the problem with surround in cinema – what do you put there, unless it’s an action movie, when you can put all your bangs, crashes and bullet zips all over the place. Otherwise, it’s mostly ambience or spot effects and Ambisonics is, of course, great for ambience, not quite so useful for spot effects, though.

CFR: Is there a particular Ambisonic recording you are proud of? Can you share that experience with readers?

JL: There’s some great stuff that I’ve recorded at air shows and some really nice music recordings, although the best one, with TetraMic in the middle of a small orchestra, can’t be shared because of copyright issues. I can tell you that entire session involved two tetrahedral arrays, a mid-side pair and a Schoeps DMS set up and the recording took place in a deserted warehouse during an opera where both the performers and the audience moved all over the building: only the orchestra stayed static. This is a screen-shot from the mix-down session for the composer’s reference CD.

My thanks to John Leonard for sharing his thoughts with all of us.

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