The Karlín Musical Theatre in Prague installed Naostage’s automatic and beaconless tracking system, K System, as part of upgrades to its AV systems.
The theatre is the third oldest and second largest theatre in the Czech capital. Famous for its staging of musical productions and operettas, most of the theatre’s shows are musicals.
Leading the installation was Petr Štásek, technical consultant at Pro Music, Naostage’s distributor for Czech Republic and Slovakia. The technical team installed an L-Acoustics L-Isa audio system with a nine-cluster frontal system providing high horizontal resolution. “The next logical step was to track the actors on stage, so the corresponding audio objects move seamlessly with them, allowing the audience to hear the vocals naturally from the direction of the actors,” Štásek explained. Before the installation, the team carried out a test of the system to assess its capabilities at Pro Music’s local UFFO theatre in Trutnov, also equipped with a similar spatial audio system.
The venue wanted to be able to track at least 16 actors at the same time, as accurately as possible during a single show. “It’s a very challenging environment,” explained Štásek who first encountered Naostage’s K System at ISE 2024. “Each show brings more complexity, with numerous decorations on stage and actors wearing elaborate costumes.”
In Karlín Musical Theatre, the technical team installed one powerful AI processing server, Kore, to track up to 16 performers from a single box; Kratos, the software that controls the entire system, manages automation and sends tracking data in real time to third-party AV systems; and two Kapta visual sensors, made up of multi-spectral cameras, rigged above the stage area, to scan the space in 3D and in real time, one under the centre speaker cluster and the other in the back of the proscenium.
It was important for the Karlín Musical Theatre to ensure a cohesive audiovisual experience for the audience; with multiple shows performed per week, the team needed a system that was reliable and save time to the technical teams on site.
“Using L-Isa audio system, each audio object, such as microphone, instrument and effect, was supplemented with parameters for panorama, depth, width and auxiliary send,” explained Štásek. “This configuration determines the precise location and manner in which each sound is heard by the audience.” In the theatre, the technical team installed nine frontal clusters, rigged across the stage.
In the theatre, K System provides precise positioning data in XYZ coordinates, which are translated into panorama and depth information for individually tracked actors. Their voices, captured by wireless microphones, are transmitted to a spatialised sound system, allowing convergence of sound and image. “If the horizontal difference between the visual location of the actors on stage and the audio source is less than 7.5-degrees, the human brain merges the sound with the visual perception,” said Štásek. “This makes the performance sound much more natural, as the audience can hear exactly who is singing because the human brain naturally localises the sound source.” He added that this setup benefits most of the audience and not only those sitting in the centre, sweet spot, “unlike traditional stereo setups where the voice may seem to come from off-stage”.
Due to the theatre’s historical significance, the integrator faced the challenge of installing the devices in suitable locations. “We needed to be discreet in placing the Kaptas in optimal positions in a crowded stage, to avoid interference with moving decorations and other stage technologies,” Štásek explained. “It was crucial for the system to have an unobstructed view and not intervene with the theatre’s scenography, sightline and architecture.
“Without K System it would not have been possible to manage the positioning of audio objects for 16 dancing and singing actors moving across the whole stage during a live musical or theatre performance.
“This was an interesting project for us, in a challenging environment. We’re extremely happy with the result as the theatre is currently running six musical performances a week and the system simply works,” Štásek said.