“Totally digital" sound system
The fourth International Circus Festival took place at the Palais des Sports in Grenoble between 25th and 28th November 2005. After three days of rehearsals, the greatest circus artists faced a jury The final performances, presented by the famous television presenter Jean-Pierre Foucault, were broadcast on French national television. The audio system design had to overcome many technical difficulties, but, Auvitran, Izo [service provider], Nexo, Palais des Sports [production and accommodation] and Yamaha joined together to make this Festival a real technical success. The solution involved setting up one of the first French “totally digital” systems, using Ethersound technology over the entire signal path.
A single conversion and a discreet system.
Le Palais des Sports in Grenoble has an area of 2000 m2, and a maximum capacity of 6000 spectators. For the International Circus Festival, it had two rings of 12 m in diameter, where acts performed without breaks. The audience were arranged around the rings, in five stands (four around the sides and one in front). The acts were accompanied by a special band comprising a dozen musicians (wearing in-ear monitors) who played live music specially composed for the event. Some of the acts used pre-recorded material, controlled from the front of house console.
The sound distribution was provided by flown and carefully arrayed Nexo GeoS speakers on the sides and a PS-15 central cluster, one CD12 sub and two CD18 subs providing extra bass. They are all compact, high quality and high power speakers and so the sound system was very discreet. System processing was five Nexo NX242 TD controllers fitted with NXtension-ES4. As there were not enough MXs equipped with Ethersound available, a NetCIRA MS-88 provided the interface with the PS-15TB analogue controllers used in the central cluster. An Ethernet 3COM Series 4400 switch redelivers all the fibres – one that arrives (from the stagebox), six outgoing (towards the monitors, FOH etc.).
If traditional solutions were used; like tens and tens of meters of analogue multicores linking all the areas, the length of the connections and the practical considerations (trampling of cables by the animals, the danger posed by motorised devices during installation) would present considerable practical difficulties and audio compromises. Under these conditions the use of fibre optics becomes very attractive, as it gets round all these problems and provides extra immunity to various problems that analogue audio signals can’t avoid with so many connections, over such long distances.
Guy Chanal, Director-General of the Palais des Sports in Grenoble, consulted the French production specialists Izo, and their plan was to go much further than the “simple” use of fibre optics, but to implement 100 % digital installation based around the industry standard Yamaha PM5D consoles. Izo choose to work in cooperation with Auvitran, Nexo and Yamaha so that from the mic preamps up to the speaker processors there would be only the one conversion A/DD/A. “We could have pushed it bit further and used digital amplification, but we are already at the limit today …” explained Philippe Mourdon, front of house engineer for Izo. “The solution really works due to the PM5Ds at FOH and monitors, we avoid a 700 µs delay at each conversion step, thats nearly 1.5 ms per A/DD/A conversion. Using today's configuration we therefore avoid a considerable amount of latency and we do not need to worry about hiss, buzzes and noise! Let’s not forget the size and weight factors either: we do not have effects racks this year and so the control rooms are much smaller!”
The signal flow.
Three Yamaha AD8HR preamp/AD converters on stage and a fourth AD8HR for UHF receivers going directly to the monitor desk are daisy chained together for control data and the AES/EBU audio signals are converted to Ethersound by AVB32ES. These signals enter the monitor PM5D via a Yamaha mini YGDAI card. The output Ethersound signals are converted to optical fibre by an AVRED-ES. The two Yamaha PM5Ds are connected by bidirectional Ethersound transmission of signals travelling in a redundant reinforced optical fibre (the best is used at any time and switching is carried out in 80 µs) such as Fibercast. Only 5 mm diameter it replaces a 64 x 64 multicore; a total weight of under 5 kg for a connection length of 150 m. The fibre leaves the FOH control room passes up through the grid, and then down to the monitor control room. It does not pass by the floor of the ring, which avoids any accidents; there were enough clowns falling over inside the rings!
The FOH PM5D did the mixing and assignments, adding 4 signals (provided for mics at the last minute), and digital inputs for CD player and MiniDiscs. The stereo and mono mixed outputs, intended for the different speaker clusters, were fed back down the same fibre optic in the other direction, and passed through the PM5D on monitors before getting back to the stage to feed the Nexo processors and amplifiers. The monitor console can send the mixed signals to the in-ear monitors, and so there were no wedges to be seen on the stage!
At each end of this 64 channel bidirectional link there was an AVRED-ES. This bidirectional link is essential: the FOH PM5D receives the stage mic and UHF mic signals from the monitor PM5D, and sends back the various premix monitoring and CD player signals. The front of house console also controls the amplification and it controls the AD8HR preamps via the Ethersound network, all down the same dual fibres. So the return lines are not simply the left, right and mono, but also pre mixes for monitoring, the playback sources and the processor, amp and preamp control data.
Support for the use of Ethersound protocol and equipment came from the local Grenoble company Auvitran. They supplied the AVB32ES, for converting the 16 AES/EBU digital stereo inputs into Ethersound and the AVRED-ES for conversion to fibre, system monitoring and management. Yamaha Mini YGDAI AVY16ES cards were also used to get the Ethersound signals to and from the AVB32ESs and the PM5Ds. To manage the system, a computer with WiFi router installed at the FOH console allows the wireless MXs to be controlled from FOH or anywhere on the floor.
As Stéphane Brocard, Commercial Manager for South-East France, says, “We are trying to put in place more and more of this type of technical partnership between Auvitran, Nexo and Yamaha, for example. Areas that service providers need to optimise are size and the number of people present at a performance. Such a complete digital system greatly reduces space and weight and so is a trump card for a service provider who knows how to set it up and use it".
About IZO
Managed by Pascal Lacroix, the service provider company Izo has two sites, in Grenoble and Besançon. It employs 9 permanent staff, and has an assembled pool of equipment over 2 x 1000 square meters, mainly relating to three types of services: live shows, events and hire.
About AUVITRAN
The company AuviTran (Audio/Vidéo Transcoding) was established in March 2003 in Grenoble by three renegades from Digigram. Within their company, they have pursued the development of solutions based on the Ethersound bidirectional audio protocol. Today, they offer a range of products based on this protocol, most of which were used at the Circus Festival.
