Turbines to triangulation: this is Kraftwerk.
The vast cavern that is Turbine Hall at Tate Modern is approximately a hundred metres long, thirty high and just over twenty wide. It’s a typical industrial space, all flat concrete surfaces, a couple of jutting glassy protrusions, and a flat steel roof with a central glass belvedere running most of its length. A more unwanted recipe for an amplified sound environment you could not wish for. Yet here we are, and to make matters worse Kraftwerk have determined to perform in 3D, not just visually but also in the audio dimension.
Kraftwerk had tried to do something like this in New York at the Museum of Modern Art (MoMA) last year. Vier Bayer from d&b audiotechnik and an old friend to the band was there and when he realised what it was they were trying to achieve put them in touch with his colleague Ralf Zuleeg. “I had been working with field arrays of loudspeakers and Wave Field Synthesis (WFS) as developed by the Fraunhofer Institute,” explained Zuleeg. “The algorithms Fraunhofer developed are licensed to Iosono and run on their IPC100 processor. There is a defined difference here; put simply surround sound, 5:1, 7:1 whatever, only really works in a spatial sense for listeners sat centrally in a pre-determined sweet-spot. With WFS all listening positions within an audience area can be in the sweet spot. This is why Iosono is typically used in cinema systems, placing all the audience within the action.”
Zuleeg it emerged, had in collaboration with Tony David Cray, Head of Sound at Sydney Opera House, achieved notable success with a presentation of the opera Die Tote Stadt, but by his own confession, “I was more interested in exploring how this combination of our loudspeakers and WFS could be exploited for a more concrete and realistic rock concert experience. d&b is installed in a club, Zapata’s, in Stuttgart, and d&b have for some time now been working with local bands to get a feel for how we can refresh and revive the listening experience of a typical amplified concert in this way. System design with a classic Left/Right PA has gone as far as it can, it’s very good compared to what we had even ten years ago, but sound engineers are becoming frustrated with its limitations. Following the concerts at MoMA Kraftwerk visited Zapata’s and in Zuleeg’s words, “used it as a playground.”
To deal with the thorny issue of the Turbine hall’s acoustic Winfried Blank, the band’s doughty tour manager, arranged for Blackout to hang a small football field of heavy wool drapes around the walls, including a massive section above and to backstage to stop audio energy leaking back through the remaining unused two thirds of the hall. “We got the reverb down to 2.1 sec at 1 kHz; 4.3 sec at 125 Hz,” said Zuleeg. “If you relate this to hall size it is OK.” More than OK, front of house engineer Serge Gräef was able at will to reintroduce reverberation through the system, and in a dynamic, room like manner; rolling it up and down the hall. How is all this achieved in practical terms?
“So we fill the room with powerful loudspeakers pointed in all directions,” began Zuleeg somewhat mischievously. “Well, the reality is we have what you might perceive as a conventional L/R arrangement using the d&b audiotechnik V-Series line array. Then across the top of the virtual proscenium above stage are four smaller arrays of T-Series equally spaced. In the room we have a large truss rectangle flown just above the audience at head height, on which we hang a large number of Q10s.” The whole system is composed of d&b loudspeakers, including further T-Series and M4 wedges on stage for side fills and monitors. It is supplied by Dobson Sound (more on them later). As Serge Gräef said, “this is not surround-sound; it’s something far more sophisticated that immerses the audience within the performance.” That was certainly true in the experience; imagine a room with almost a thousand people as we had this night, all wearing 3D spectacles for the constant stream of 3D movies played across the 14 m wide screen just above the band’s heads. Look back from the stage and the vision of the audience is somewhat detached and disassociated from the proceedings, that little barrier of cardboard and polarised filter sets them apart. Yet to see those blank eyeless faces is to witness an automata effect as they sway and swirl with what they are hearing. Where does this motion come from? Mostly the music as it directs in, through and around them.
In truth the more powerful front array does impart some familiarity of listening experience, but then magically it subsumes into this greater whole where, for want of a better expression, invisible loudspeakers positioned we might imagine, far outside the confines of the venue, start to broadcast sound. “The purpose if you like is to realise Kraftwerk’s music as conceived,” explained Zuleeg, “placing the instrument sources into the audience. There is a constant direction for basic sound, then the musicians or engineers can move certain sources around, pretty much where and when they want.” It’s almost a promenade concert, were Kraftwerk to be playing violins say, it would be all too easy to close your eyes and imagine them walking amongst you.
As was said, the PA system is supplied by Dobson Sound; Mark Isbister is their systems man for the event. No shirk himself when it comes to modelling sound, how did he find working with this conceptual audio experiment? “I’ve heard nothing like it before.” Is it a gimmick? “Well it’s certainly valid in this instance and I can think of quite a few more applications where it would be welcomed. It’s certainly well suited to this kind of music. It’s not just the effect that has impressed me; it’s the implementation, by the band, by d&b, and by the band’s technical team. It’s something you could easily get wrapped up in, lose touch with the music, and just obsess the technology; but they’re all incredibly relaxed and workmanlike and just get on with it. The thing I notice most, especially in an acoustic environment such as this, is the spatial image from the stage, you don’t have to be in the midst of the PA to enjoy it.” From a practitioners point of view, is there any down side, would it be practical to put up a rig such as this in a touring environment? “You do have to spend time getting the speaker positions absolutely precise, so we spent some time with tape measures when loading in. But touring it would be little different from lampies getting their moving heads in exactly the same place every day.”
Having experimented with quad, and with theatre like surround systems, Kraftwerk has taken a big step. More than anything this WFS based system presents the sound much more clearly. Why it’s worth the effort is purely logical; if the band want to present 3D video then the same should be possible for sound; apparently this has been an aspiration of theirs for several years. The clarity comes directly as a result of applying WFS; listeners don’t suffer the masking effect that accompanies the typical dynamic push and pull of conventional system mixing. From a front of house control position its simpler to achieve than you might imagine, much of the source placement is pre-determined and then triggered by time-code; this removes a lot of pressure and allows for the more playful and intuitive added positional effects that the band produces live. This makes for a complex and satisfying tapestry of sounds.
The audience experience is everything in the end, and Felix Einsiedel who developed the middleware for the control interfaces had an interesting perspective on this "It is true, it’s unconventional and people are not used to it. Ask them and they usually say, ‘go back to playing it through the stereo system’. Then when you do that they are startled by the difference. ‘Go back to the WFS system’ they say.” So like flat screen TVs and 3D video, you might not like it at first, but when you step backwards you soon realise this is progress.