A Parisian theatre has designed and installed a 3D sound system that gives a consistent soundstage throughout the seating areas. Tom Bradbury finds out how it was done.
A 3D sound system, comprising components from Amadeus, Solid State Logic (SSL), Lab.gruppen and Sonic Emotion, has been installed at Paris's historic Chaillot National Theatre. The four companies joined forces to design a bespoke electroacoustic sound reinforcement system, which has already been used in contemporary dance productions at the theatre.
Amadeus envisaged a new sound reinforcement system for the 1,270-seat Jean Vilar Hall that would go beyond traditional formats such as stereo or 5.1, or conventional speaker systems. The solution uses wavefield synthesis (WFS) – a process that creates a soundstage by preserving the spatial information (distance and direction) relating to the sound sources used.
"This technique allows us to replicate the sound field's physical properties. Wherever they are in the theatre, the listener keeps a coherent perception of the sources' localisation," explains Marc Piera, Chaillot National Theatre’s sound department manager.
The Jean Vilar Hall's seats are arranged in sections different sizes and slopes (16°, 23°, 25° and 35°). The control room sits 12m above the ground. The spectator area is 33m deep and 34m wide.
Wave field synthesis makes it possible to create acoustic waves that appear to emanate from virtual sound sources. To do this, the system uses a large number of loudspeakers, each controlled with a delay and a gain to form a wave that appears to emanate from the desired location of a virtual source. This process is repeated for each sound source in the sound scene. The technique creates a coherent sound field over an extended area, preserving the fidelity of the spatial image wherever listeners are located.
Same sound everywhere
Denis Desanglois, the theatre’s technical manager, says: "We implemented a WFS-based system prototype and asked the companies we were working with for their feedback. Some technicians were totally initially disoriented, but eventually everyone was happy, technicians and artists alike. The sensations of listening are completely different, wherever you are in the hall, you experience the same sound, that's pretty amazing.
"We even integrated a 24-speaker ramp in the front end of the stage, to avoid the usual 'sound hole' in the first row of seats!" adds Desanglois. This line of passive coaxial loudspeakers that are 4-ohm variants of the Amadeus PMX 4 model (4in LF, 0.4in HF), form a large-scale 'soundbar'; they are distributed 75cm apart across an 18m width, and seamlessly cover the first row.
The second line of speakers, which covers the first two-thirds of the raked seating area, consists of 11 Amadeus UDX 15 active coaxial speakers (15in LF, 2in HF), with remote bi-amplification. These loudspeakers are evenly spaced across a 23.5m width and at 9m height. A third line, of 11 Amadeus UDX 12 active coaxial speakers with remote bi-amplification, is hung at 9m across 23.5m (identical spacing between each of them), and they are placed at 9m height. This line covers the first two-thirds of the seats.
A fourth 'Surround' line, made up of six Amadeus UDX 12 active coaxial speakers (12in LF, 2in HF) with remote bi-amplification, is hung from the second technical bridge. A bass reinforcement system is set up the first-level technical bridges, on the left and right-hand sides: it comprises six Amadeus Maestro subwoofers, each hosting two long-excursion speakers, loaded by a folded hyperbolic horn.
Completing the sound system is an SSL Live L300 digital mixing console, used with four SSL Dante stageboxes: two Network I/O SB 8.8 and two Network I/O SB i16 (with eight and 16 analogue inputs each respectively). These feature SSL’s SuperAnalogue technology for clarity and precision.
Audio over IP
Philippe Guerinet, director of international sales for SSL and manager of SSL France, says: "We were impressed by the warm welcome received by our SSL Dante solutions in the live and broadcast sectors… [Audinate’s] approach is innovative, reliable and affordable in every aspect; the Chaillot National Theatre install is an excellent illustration of this."
He adds: "Audio over IP allows us to put the stageboxes where needed, with minimal and redundant cabling, and to connect on the network all kinds of Dante-enabled gear: Amadeus sound reinforcement system, SSL L300 console, SSL Network I/O stageboxes, and every other ancillary equipment needed.
“This network approach notably allows us to solve classic problems, like signal distribution without adding any TDM routers; there's no loss, nor noise induced in the audio signals, and latency is particularly low. Last but not least, the technical solutions chosen by the Chaillot National Theatre ensure total flexibility and an astonishing audio quality, for a surprisingly affordable budget."