Immersive audio – the sound of technological sophistication

At the latest German-speaking stage-sound engineers’ meeting on 27 January 2020 in Zurich, participants found out first-hand how the Zurich Opera creates and uses immersive audio. The theatre has not only installed electroacoustic systems in the stage and seating areas for variable house acoustics but is increasingly using innovative sound technology, including 3D, for scenic effects on stage.

The meeting of 50 participants from the German-language theatre scene at the Zurich Opera was made possible by Jürgen Hanelt, chair of the stage branch of the association of German sound engineers (VDT), and Oleg Surgutschow, head of sound at the Zurich opera house.

After some words of welcome, Surgutschow recalled the dogged and time-consuming work of equipping the auditorium with the right loudspeakers. As late as the mid-1990s, some auto speakers had been permanently installed here, connected to 100 V circuits. A test was done to compare possible alternatives, which resulted in the theatre acquiring d&b F1220 systems in mobile units. To fit the limited space in the portals, the company d&b came up with especially small E2_z (‘z’ for Zurich) speaker lines, which have now been replaced by digitally controlled systems. After another test-case comparison, the theatre acquired d&b Q line arrays, designed to be hung temporarily in the portal, and connected to subwoofers. The last, trickiest step involved replacing several ceiling and wall speakers in all the circles with integrated, colour-coordinated, high-performance speakers (>60 x d&b E4) to create an immersive audio experience in the space.

We were then taken on a tour of the theatre, including the control booth behind the dress circle, where we found a Lawo mc² 56. The 48-fader console has a portable counterpart for setting up in the house. This second console provides 32 faders that can be operated via a 16-channel extension. The portable operator panels can be configured as reflective surfaces or for combined operation.

Listening practice

With its sophisticated playfulness, the mixed architectural style of the building is undoubtedly impressive. For us audiophiles, an even more intriguingly playful aspect was provided by the SpatialSound Wave (SSW) system by Fraunhofer IDMT and the many loudspeakers in the space – to close the tour, our Zurich colleagues had prepared some listening situations in the stalls. First, we were played excerpts from a concert recording of Verdi’s Requiem. The various instruments were scattered acoustically across the entire space so that we found ourselves positioned between the musicians. Transporting a large orchestra to a virtual space and breaking up its original arrangement to give it a different shape challenged all our listening habits and marked an unheard-of experiment for an opera theatre!

A performance by two violinists in the orchestra pit then gave us an idea of the actual acoustic quality of this space with its concave ceiling over the pit. In 1.4 sec reverberation time, an extraordinarily beautiful sound, with locatable sources, was created in the stalls from these two instruments, setting a high benchmark for all further attempts to electro-acoustically put these signals in other spaces. Our Zurich colleagues had prepared various space parameters for just this task, immersing the sound of the violins in ever larger spaces, right up to cathedrals. That works very convincingly with the SSW parameters and of course the necessary dedication put into adjusting the speaker system. In fact, it underlined the locatability of the sound sources.

Lastly, we were surrounded by multiple musical instruments, appearing acoustically one-by-one, all with directional stability and convincing quality. These were play-ins for the Zurich ballet production, choreographed by Christian Spuck, of the opera Das Mädchen mit den Schwefelhölzern by Helmut Lachenmann. During performances, the orchestra musicians and singers are spread among the audience, positioned on different levels in different boxes. In this way, the frontal situation is suspended, and the visitors share the space with the performers.

A total artwork for all the senses

Subsequently, Mike Utz, deputy head of the Zurich Opera’s sound and image department, told us more about the above-mentioned ballet production choreographed and directed by Christian Spuck, which was the stimulus for many of the theatre’s new technological acquisitions in 2019. Conceived as “music with images”, it is based on a story by Hans Christian Andersen and texts by Leonardo da Vinci, Gudrun Ensslin, Ernst Toller and Friedrich Nietzsche, with music by Helmut Lachenmann. The production presented the theatre with unprecedented challenges: The orchestra was too large for the pit and the set left no room for the choir on stage. Several recordings were to be played in parallel, handled by individual musicians. The dancers did not have any clear cues in the music.

One of the first tasks was to organise spaces for everyone involved. Second violins, violas, four additional sets of percussion and 16 vocalists needed to be positioned in the auditorium. They were spread across various boxes and the second circle. The organ and seven CD players with the seven musicians operating them could only be accommodated in the choir hall, located in the new building.

To be able to instantly adjust the sound to different circumstances, a Lawo mc² 56 console was set up in reflective mode in the last row of the stalls. As the orchestral instruments were spread out throughout the house and in some cases needed extra amplification, one mobile stagebox (DALLIS) per side was installed in the second circle and connected to the Lawo Nova73 Core via LWL-MADI.

The two soloists and the 16 vocal soloists were equipped with wireless microphones, some stick-on, some with headsets. Individual voices in the orchestra pit were also amplified via microphones. The sound of the organ and seven CD players was transmitted via a mini mixer in the choir hall connected to the main mixing desk by four analogue lines. In total, then, approx. 80 input channels were in use.

The existing SSW 3D surround system was the ideal operating platform for the spatial distribution of the instruments. Thanks to the Lawo mixing desk it was possible to work the necessary number of channels without having to change the hardware configuration from that of other performances.