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Steve Hackett

explains Ambisonic recording (3D sound)

Aural sensation! Guitar person experiments with 3-D sound. Jon Lewin dabbles with typewriter.

Ambisonics! Psycho-acoustics!! Steve Hackett!!! All words clearly designed to strike horror and revulsion into the heart of the discerning follower of modern music. But what are these strange, exotically-termed things, and what possible bearing could they have on good old rock'n'roll?

In reverse order: Steve Hackett is a musician and one-time member of Genesis. He has had Top 20 LPs and a Top 30 single in his own right. He has a new album available this month, called "Till We Have Faces"; it is the first rock record ever to be recorded using ambisonic techniques.

Psycho-acoustics is, approximately, the study of what happens between the ear the brain, and how we understand sound. Ambisonics is what you are reading about. Tell us, Steve.

"Basically, it's circular sound. Not like a holographic head, which is just clever stereo — it's something you can use during the mix to place sounds all around you. And it's not like quadrophonic, because the only appendage you need to add to an existing stereo system is a decoder, which you can get for only £70, and another set of speakers.

"It makes things sound more live... it puts you in the middle of the toyshop, rather than leaving you looking through the window. The BBC have been doing experimental ambisonic classical broadcasts, and they say it gives a 30% wider stereo effect. The separation is bigger... it just sounds very different."

But Steve, how do/does ambisonics work? Why do humans, with their meagre two ears, need anything other than stereo? "Well, I'm a layman, an ears person, who's come to it and found that it works. I'm not up with the technology, that's all explained in this idiot's guide here." As I took the pamphlets, I heard the editor's fateful words tolling in my ears: "...get him to tell you about this ambisonics thing..." It sounded simple enough, but then I hadn't read the explanations.

Putting it simply (spot the misnomer), ambisonics attempts to create a field of sound around the listener, thus giving recordings all the added ambience that you would expect from a live performance. It does this by subtle manipulation of the laws of psychoacoustics: the ambisonic image cheats the brain into hearing the subtle echoes and natural reverberations that typify "live" acoustics. It does not perform whacky unnatural tricks, such as placing an instrument in each corner of your room. According to the National Research Development Corporation, which is responsible for co-ordinating research into ambisonics, it should be able to "reproduce the directionality of indirect reverberant sounds, as well as of direct sources." This gives the impression of surround-sound, or "periphony". Back to' Steve.

"I discovered it at Marcus Studios, where I was recording and mixing the new album. They had it, and suggested I use it. I try always to be open to new ideas like that, so I thought 'why not?'. It's very quick to use, so we didn't waste any time, which would have been off-putting. We added it at mixdown, like an effect. You only have to apply it then, unless you're designing something as an ambisonic experience. But it's not just an effect, though."

Too right it's not — it's fundamentally a new method of mastering recordings, and as such is v important. This is how it works (roughly). Ambisonic recordings are mixed from multitrack onto 4-track: the four put down are as follows: 'W' is true mono, an omni-directional signal incorporating all sounds with identical gain; 'X', 'Y', and 'Z' represent the directional sound around the listener, being front-and-back, left-and-right, and up-and-down respectively. This 4-track recording is known as B-format.

"The next thing I do, if ambisonics takes off, which I hope it does as I find it very exciting, I will treat the LP differently, use the ambisonics more. It could change the character of the music — there's no real parallel, as we've lived with stereo and its limited dimensional field for so long now. I'm bored with stereo — I'm looking for something else."

In order to avoid a Quadrophonic-style technological disaster, the NRDC have sensibly specified that B-format must be made to conform to the Universal HJ system, or C-format. C-format works off traditional two channel stereo. This means that ambisonic encoders must be capable of combining the 3-D sound of W, X, Y, and Z into (almost) ordinary stereo, which enables us humbler mortals to listen to ambisonically recorded things on our Dansettes without them expiring of future shock.

"We mixed the new album on 48-track, as we'd used up nearly 24 on percussion when we were recording in Brazil. I just love detail in things, so I didn't want to bounce down and lose any. That's why ambisonics is so good, as it helps preserve detail, because it gives you much more room to place things in."

In the studio, these C-format UHJ encoders work to a basic two channel system, left and right, which gives good (30% better, we have been told) stereo. But they can also carry the extra information provided by our original W, X, Y, and Z recorded sound-fields.

At home, for the listener to gain access to these, a UHJ decoder is necessary. But where is this extra information, I hear you cry? Obviously, stereo records and tapes only carry two channels. But more modern, more complex media are capable of providing much more information: 4-channel FM radio broadcasts, compact discs, digital discs are all possible sources of full periphony, the mighty ambisonic surround-sound.

"Recording in Brazil gave me a fantastic chance to get out of the rut I felt I'd got into; I find that disorientation helps the creative process, gets the juices flowing. Everything I've done in the past has been very careful; now it's just play what the hell I want — happy accidents. I've done things that were very structured, every note — that doesn't take enough chances. I like not to know where I'm going."

The domestic UHJ decoder unscrambles W, X, Y, and Z and redirects their signals (via a power amp or two) to the relevant speakers, of which there must be a minimum of four. The use of such interesting devices as the phase-amplitude matrix, and a "layout" control to compensate for the shape of your listening room, permit the fiendishly clever ambisonic recording to fool you into believing that you are centrally located in a very maelstrom of sound. Phew.

To get my own back on Steve, for making me try and understand all this, I asked if he thought that applying an effect as refined as ambisonics was in tune with his new-found stylistic freedom? "It depends how you're using it — for placing sounds, or just for effect. We'd place the stereo echo/reverb behind, instead of to one side as you would normally. We didn't use any of the ambisonic technology — mics and things... so I think it can work for rock.

"I do know that it got me excited about recording again, which must be good. Listen to the album, and you'll hear the difference."

I did. And I could. Although it was a natural reaction just to reject the idea of ambisonics out of hand, I could actually hear on my own hi-fi (very ordinary stereo) a greater lushness than from an ordinarily produced LP. I had thought that Steve Hackett might have been confusing his excitement at recording in S. America with a mild attack of enthusiasm for a new gimmick; ambisonics is not a gimmick.

"Whether the timing's right for it, I don't know. Maybe it'll be rediscovered one day... trouble is, you have to galvanise the makers, not the public. The public are ready..."

If you are ready, Steve's new record, "Till We Have Faces", is out now on Lamborghini Records. Ambisonically.

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Yamaha BB1600/Aria 5-string

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Beyond E Major

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One Two Testing - Nov 1984

Donated & scanned by: Mike Gorman


Steve Hackett



Related Artists:


Interview by Jon Lewin

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> Beyond E Major

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