44 l January 2013 installationreport 12
The Rafik Hariri auditorium was the venue for this exciting development in wavefield synthesis
www.psneurope.com
number of loudspeakers in the ‘main’ WFS array
The WFS system includes
12 8” coaxial biamplified loudspeakers, placed on the front edge of the 20m-wide stage, 120cm apart: that’s the ‘main’ WFS array, covering the first half of the hall (sound pressure for the first rows and global spatialisation effect). Then there are seven 12” coaxial biamplified loudspeakers suspended 9m above the stage: this is the ‘support’ WFS system, aimed at the second half of the hall, for the furthest seats. There are seven subwoofers on the ground, in front of the stage. “All these speakers are made
FRANCE
WFS premiere in Paris Arab World Institute
An exciting variation on established wave field synthesis systems made its debut in a French performance space last month. Franck Ernould reports
THE PARIS Arab World Institute (AWI) building was inaugurated in 1987. Designed by Jean Nouvel, it hosts several museums, a school, a restaurant, a library and the 430-seat Rafik Hariri auditorium, which regularly hosts conferences and concerts. A square-shaped hall, the Hariri has high ceilings and is acoustically challenging – reverberant in the highs, absorbent in the mids and reverberant in the low-end. Hariri’s incumbent conventional
sound reinforcement system was giving unsatisfactory results, it was reported. Time for an upgrade then, and hence acoustical consultants Patrick Thévenot and Jacques Fuchs of Taylor Made Systems were called in. The colleagues specified a significant development in the capabilities of WFS (wave field synthesis); the system was subsequently installed and tested and members of the pro-audio community were invited to hear it in action.
“We could have gone the line
array way, but we thought the wave field synthesis approach was more interesting,” Thévenot says. “We knew Sonic Emotion was working on something, and we conducted some experiments here with them in 2011, with a dozen speakers hanging above the edge of the stage. It already worked well, and we just decided to wait for the forthcoming improvements of the WFS processor software…”
Sonic Emotion present their findings
A dozen speakers only? Wave field synthesis is all about artificially recreating the original sound wavefront with a large number of individually driven small speakers. When properly executed, sound seems to originate from virtual sources, and localisation doesn’t change with the listener’s position. (The Fraunhofer Institute’s forays into WFS research resulted in the creation of the IOSONO technology and brand.)
Until now, it was mandatory to use more than 100 speakers placed all around a room, as close as mutually possible, to improve spatial resolution. It was complicated, expensive and high SPLs were out of reach, as speakers were too small. (You can hear such a system in Paris IRCAM, using 264 Amadeus custom-made active coaxial 10cm speakers placed all around the Sound Projection Space.) Sonic Emotion, a Swiss company specialising in 3D sound and an expert in WFS and designer of the IRCAM set- up, was aware of this limitation. But instead of following the established ‘laboratory’ way (increased angular precision, more and more loudspeakers), Sonic Emotion engineers began to tweak their algorithms and work with the software rather than the hardware. Their goal: to be able to use fewer, and bigger, loudspeakers, in order to achieve higher SPL but maintain natural localisation and coherence. Sonic Emotion’s research into the issue resulted in the use of distinct layers of loudspeakers, with subwoofers to boot. All these key points are now
integrated in version 3.0 of the Wave 1 Sonic Emotion processor, which accepts 24 input signals and now includes crossovers, equalisers and limiters on each of its 32 outputs – with no need for external processing. It is this Wave 1 processor
which was used, for the first time, in the Rafik Hariri auditorium.
by APG, following TMS specifications, with specific criteria for increasing directivity, group delay and power handling,” says Thévenot. “Original loudspeakers and filters have been modified, but the boxes are off-the-shelf. We use
Lab.gruppen C Series amplifiers and DirectOut MADI interfaces to transport the audio signals.” The WFS system is able to generate 108dB SPL +/-2.5dB across the whole hall. Listening to a powerful WFS system like this one is an interesting experience, and your correspondent was invited to do just that. The sonic impact is apparent, the sound localisation too – listeners were asked to walk around the hall while musicians were playing on stage, left/right and front/rear. It is quite the revelation to observe that even when a person is in front of a speaker, blocking it, there’s no ‘masking’ effect as there would be with a conventional system. There’s no need to mix specifically for WFS, either: the idea is to send a stereo, 5.1, 7.1, 9.1 mix into the system, and to place, on Wave Performer’s graphical interface, the sound sources where you want them (your 5.1 speakers, for example). The processor then translates this into treatments (EQ and delays) on every output, recreating a coherent sound image. There are ways to edit the spatialisation in real time – a Sonic Emotion representative did that on his iPad while moving around the hall. The AWI installation and Sonic Emotion’s endeavours have shown that wave field synthesis can push through those laboratory doors and find a home in a more practical, real-world environment. Let’s see where it travels to next. n
www.sonicemotion.com
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