The following is a continuation of a discussion from You're Surrounded, Part One. I use surround in many ways to achieve different effects, to enhance atmosphere, to unnerve or frighten an audience, or to recreate a particular acoustic. I use it to immerse an audience in sound where I think it’s appropriate and won’t distract from the action on stage, but I never place sounds in the surround speakers, just because I can.
Apart from anything else, I work in venues that vary from one to the other, from tiny spaces above bars or in basements to multilevel playhouses seating thousands, so there’s never a one-stop approach to the use of surround, even if the production has the funds to afford it, and the venue has the infrastructure to support it. Decisions are made with regard to the play, the venue, and, all too often, the budget, but if I don’t feel a soundtrack of mine warrants it, I don’t ask. That said, I do love to use surround when it’s appropriate, and in many of my recent productions, it’s played a major part in my designs.
As with my earliest work, pan-potting mono or stereo sound effects to sets of loudspeakers is the most straightforward way of adding effects to a surround system, either by direct routing in the playback system or by creating a multichannel file in your DAW or editor. All the major audio programs can achieve this easily with surround panners and multichannel output possibilities; although as these are usually aimed at film, television, or music mixers, be careful to check that the output designation is as you expect (see my rant at the end of this piece for more details).
This type of routing for surround almost always works well, providing that a suitable distance can be maintained from loudspeaker to nearest audience member, and there is an increasing number of sound effects libraries recorded for use in surround systems, although almost all of these, once again, are aimed at the 5.1 systems used in film and television. Recording in surround is pretty easy these days, with all-in-one 5.1 and 7.1 microphones being offered by the likes of DPA, with the DPA 5100 surround microphone, affectionately known as The Bicycle Seat, and the various offerings from Holophone Microphone Systems.
Both these systems use discrete miniature electret microphone capsules in a special enclosure, with each microphone feeding a separate channel of a multitrack recorder. Schoeps offers a different approach, with mountings for its small diameter capsule (SDC) microphones in various surround configurations and a microphone/software system, which the manufacturer calls Double Mid/Side, where a rear-facing cardioid is added to a standard mid-side pair, and the resulting three channels are trans-coded in software to provide a 5.0 surround output.
>All of these systems have their advantages, but they all produce an end result that is aimed squarely at a world that is not ours, and that’s where the latest developments in Ambisonics start to look interesting. Initially, as I mentioned in the previous section of this article (November 2014), the recording and playback of material recorded using Ambisonics relied on expensive, often custom-made, hardware; but with the major advances in digital signal processing (DSP) and the ever-increasing power of computers, software can achieve the same thing with relatively low cost. Recordings can be made using a special microphone using what’s known as a tetrahedral array, where four identical microphone capsules are arranged in a specific way to capture sound from a 360° sound field. UK microphone and mixing desk manufacturer Calrec developed the first commercial product, simply called The Soundfield Microphone, the device used to capture the concert that I first heard back in 1979. The basic design hasn’t changed since then, and there are now alternative versions available at varying degrees of cost.
One of the major advantages for me in using a Soundfield-type microphone is that you can post-process after the event, even if all you’re doing is creating a stereo or mono version of your all-singing and dancing full-surround-with-height recording. You can rotate, tilt, spread, or narrow the recording angle, and, with some of the more advanced software, you can create an array of virtual microphones with different characteristics, from omni, through figure-eight through to hyper-cardioid.
Without getting bogged down in too much detail, Ambisonics is a way of recording and reproducing surround sound in both horizontal and vertical surround. You can read the relevant Wikipedia entry for an explanation of the basic science behind the technique. At its simplest, what’s known as a B-Format surround signal can be generated either by software manipulation of mono sources or by a Soundfield-type of microphone and can then be transcoded for output in many ways, from a single source in mono to multi-speaker surround arrays.
For a long time, the biggest perceived problem with Ambisonic surround was that, in its basic format, known as First Order Ambisonics (FOA), it had a very small sweet spot, which made it not particularly suitable for large-scale playback. However, I liked it for theatre use mostly because it didn’t sound wrong, even when you were outside the sweet spot, and for atmospheric effects, it worked really well, even in difficult spaces. It may not have had the wow factor that a well panned stereo effect can achieve, but I found that it was much more successful at transporting an audience to a location without causing a distraction from what was happening on stage.
Recently, however, there have been major developments in the use of Ambisonics, particularly with the arrival of immersive virtual reality systems such as the Oculus Rift, and it’s now entirely possible using software, to enlarge the sweet spot and even to deal with irregular speaker arrays. One of the developers in the forefront of this technology is a company called Blue Ripple Sound, and the really good news is that the core software to experiment with this is free, with the caveat that it only works with certain DAWs at the moment. In fact, quite a lot of the software that’s being used to examine surround in large-scale systems is free, because it’s being developed in academic institutions where the focus is on advancing knowledge, rather than creating proprietary systems that lock the user into one specific system. Are you listening, Dolby?
If you do want to test the water, and you have Reaper, ProTools, Steinberg Cubase or Nuendo, or Apple Logic, there are a couple of ways you can achieve this at no cost, other than some time to read and understand how to set your system up. There are a number of software plug-ins that will decode audio material recorded as B-Format surround, but probably the first stop should be the plug-in specifically designed to deal with the output of Soundfield Microphones. The company is now part of TSL Products, and the SurroundZone2 plug-in is available for VST, AU, and AAX systems, with VST and AAX available for both Mac OS and Windows systems. You can download it for free here.
If you want a more advanced version, the truly excellent Harpex-B plug-in isn’t free, and in fact, it’s quite expensive, but there’s a 30-day free trial available, which is worth experimenting with. If you’re a Windows user and prepared to dig a little deeper into the system setup, then you can try Dave McGriffy’s VVMic VST plug-in, which as the name suggests is a VST-only plug-in. Want to dig deeper still? Daniel Courville has a whole suite of software, including a Double M/S version and one for making your Zoom H2 surround recordings sound pretty good.
Want More Material?
There’s even more good news for those of you who want to experiment with Ambisonics in surround. Not only is much of the software free, but there’s quite a lot of material to play with, which is also free. Isn’t that wonderful? What’s more, I have recorded some of it, which is also wonderful. In fact, that’s my original location kit in the picture at the top of the page.
Want to try more material? You can find these and many other Ambisonic recordings here, including sound effects, music, and specially composed electronica. However, you need to understand the process for retrieving files from the site and then preparing them for playback. The Ambisonia site uses a torrent distribution system, and you won’t get a useable file until the torrent client (there’s one built into the Opera web-browser, and various other freeware versions are available for Mac and Windows operating systems) has finished downloading the whole file, which may take a while. Ambisonia gives you a choice of two types of file: .amb files and DTS-encoded files, which you should ignore for the purposes of this article. The .amb file is a special form of a WAV-EX file, comprising interleaved B-Format four channel files, which can then be downloaded or streamed for decoding. (See here for a very detailed explanation).
Very few DAW programs recognize the .amb file extension, which is a pity, as it’s essentially just a multichannel .wav file that any DAW is actually capable of using. For example, attempting to import an .amb file into Nuendo using the Import Media command from the menu doesn’t work, but simply dragging a file into a pre-existing 5.1 track does work. If you’ve got the fantastically useful TwistedWave program (Mac only, sorry) then you can import an .amb file and save it as a standard .wav file, and then it should work in any DAW capable of supporting multichannel audio tracks.
The raw .amb files as they stand are not in themselves decoded surround recordings. They contain specially matrixed audio information that can be decoded into mono, stereo, 5.1, 7.1, or binaural surround recordings with the appropriate software plug-ins, so attempting to play back the raw files will not give you any kind of coherent result. The file must be placed into a multichannel track and routed to a multichannel output with a suitable plug-in inserted in the chain to give you access to the various ways you can decode a B-format file.
Want to buy a mic of your own? Aside from the DPA, Schoeps, and Holophone systems outlined earlier, tetrahedral array-type microphones are available from TSL, as mentioned above. Core-Sound produces the TetraMic, and a new, Kickstarter-funded company in India produces the Brahma microphones, which are also causing interest, especially as they’ve managed to build one into a Zoom H2N body, making it the smallest complete surround recording package available anywhere. You’ll find that there are two types of tetrahedral arrays on offer: those from TSL/Soundfield that output a B-Format signal, which supplies a matrixed four-channel signal, where the four channels are designated W, X, Y, and Z, where W represents on omni-directional reference, X represents front and back, Y represents left and right, and Z equals up and down (this is a gross simplification, but it’ll suffice for this article). These microphones will have hardware control units that give the user options in terms of gain and directional orientation and filtering and are at the top end of the market. The Soundfield SPS200 and the Core Sound TetraMic both output simple capsule feeds and need software (SurroundZone2 for the Soundfield and VVTetraVST for the Core Sound) to correctly matrix the capsule feeds into a B-Format signal.
I know it all sounds horribly complicated, but once you get started, you’ll want to explore more. There now follows a bit of a rant. You have been warned. I was once asked to assess the sound design plans of a student from one of the major drama schools here in the UK. The person in question arrived with a detailed description of the content, which seemed to be ambitious but pertinent, and we moved on to the playback system. “I’ve devised a 5.1 speaker system for the venue…” was the opening remark, and at that point, I stopped the student and asked what he meant by a 5.1 system. “Four speakers, one at each corner of the space, and then two more in the lighting grid,” was the answer. My explanation, that this wasn’t a 5.1 system, just six speakers allocated at points around an auditorium, was met with an air of some bafflement. The student pointed out that 5.1 systems needed six channels and that he was using a DAW that gave him six channels of output for his audio and that the DAW referred to it as 5.1, so his system must be a 5.1 system. I asked if he’d actually looked up what the specifications for output designation in a 5.1 system with regard to speaker positioning and what the “.1” part actually referred to, and he admitted that he hadn’t. He departed with the distinct impression that I was a boring old pedant and killjoy (probably correct on at least one count) and that he’d go away and do his 5.1 thing, and it would be terrific. In the end, he never got it together, not having looked hard enough at another set of specifications, that of the space in which he was working, to discover that there weren’t sufficient speakers or amplifier channels to give him more than four outputs. (You can find the recommended specification for the use of 5.1 systems here.) Now you may well say that I was indeed being pedantic, but I’m rather of the opinion that if you use specific terminology, you need to know to what that terminology refers, not simply assume that, if your DAW offers you a 5.1 output option, it’s actually going to be of some use to you.
Apart from anything else, most DAWs offer a multitude of possibilities for routing for 5.1 output, with various configurations of left, right, center, LFE, left-surround, and right-surround being on offer. The foregoing configuration (L, R, C, LFE, Ls, Rs) is the version recommended by the SMPTE and the ITU, but there are others that apply in other circumstances. The situation is made even more confusing by the variety of delivery systems for home theatre use, with around 15 different formats on the books at the moment, from the original Dolby® ProLogic® through various DTS® versions and a THX version, to the latest, Dolby Atmos®, which adds height into the equation and, along with yet another proprietary full surround-with-height system called Auro-3D, is currently changing the way movie theatre audiences are experiencing surround sound. Quite frankly, it’s all a terrible mess, as is, very often, the resultant soundtrack experience, both at home and in the movie theatre.
For me, the main problem with all of these surround formats is that they are meant to apply either to home cinema systems, where the specifications for speaker placement are almost universally ignored anyway, or to movie theatres where, more often than not these days, the auditorium is a shoe-box shape, and the application of standards is fairly easily applicable, whereas most playhouses differ widely, with balcony overhangs and anything but standardized seating arrangements. The development from the original film soundtrack from a central mono speaker to music and effects in stereo and dialog in the center channel, to the addition of surround speakers, extra sub-bass speakers, and now “voice of God” speakers above the audience has been slow but inexorable in movie theatre soundtrack playback, but, with very few exceptions—IMAX systems, for example—I find the use of surround is too often gratuitous and distracting.
For theatre sound practitioners, another problem has arrived with the advent of the various schemes to film popular theatre productions and then deliver them to a wider audience via movie theatres and TV broadcast. The first time one of my shows, a period light comedy, was filmed for distribution in this way, the company involved told me proudly that it would be delivered with a 5.1 soundtrack and invited me to a pre-release screening. I watched and listened as sound effects of an event that the cast were reacting to through an upstage window were lovingly reproduced through the rear auditorium speakers, as were almost all of the other spot effects in the show. When I asked the post-production engineer why he’d done this, his response was pretty much “because something has to go in the surround; otherwise, it’s a bit pointless having it there.” I suggested that perhaps the audience reactions should be the only thing in the surround, aside from the odd distant dog, and possibly an owl or two and, eventually, that’s what happened.
I’d almost forgotten about this until recently, when a different company filmed another production, and pretty much the same thing happened. Cast members exited through doors upstage, and door slams and footsteps popped up in the surround speakers. When I questioned this, I got almost exactly the same response and had to counter with the same suggestions. Later in the process, another post-production engineer mixed the same production for cinema release in Dolby Atmos® and made the same set of, to me, inexplicable decisions. This time, I wasn’t involved in the process, and the weird routing stayed, much to my dismay, but my colleagues and I are fighting back and aim to wrest control of our sound designs away from faceless people in tiny post-production studios and back into our own hands. I’ll let you know how we get on…
For more, download for free the January issue of Live Design onto your iPad and iPhone from the Apple App Store or onto your Android smartphone or tablet from Google Play.