From the classroom to the big stage – a dream come true, thanks to 6K UNITED! Every year, the project organizers orchestrate gigantic choir concerts with around 6,000 school children, who fill the biggest concert halls on a tour across Germany. In 2024, 6K UNITED! played eight shows in six cities (Berlin, Hamburg, Düsseldorf, Munich, Mannheim and Hanover), which included a choirmaster, vocal coaches and a 17-head live band. At 6K UNITED!, the concert hall becomes the stage – and calls for a sophisticated sound engineering concept that both performs monitoring tasks for the choirs in the tiers, while enabling perfect localization for the audience. To achieve this, general technical contractor Melodus GmbH opted to combine a classic line-array stereo system with immersive audio for the front-fills, paired with a zactrack SMART tracking system.
While the choirs, including the respective vocal coaches on the stage, were panned hard left and right in the stereo panorama and thus clearly separated by the stereo system from DAS Audio, Melodus had to find an alternative way to ensure the correct localization of the near-field sound in the front rows of the audience: “In a classic front-fill setup, you normally have two options: either you have all the loudspeakers mono or alternating left and right,” explains Oliver Tschotow, Managing Director of Melodus and FOH Engineer on the 6K UNITED! tour. “While in mono, no stereo image is generated at all, the latter variant causes the stereo image to change and sound distorted, depending on the seating position.”
Tracking for immersive audio
The solution: Melodus combined the 11 front-fill loudspeakers into a loudspeaker bar using the CODA SPACE HUB immersive audio processor and automatically positioned the sound objects on two 3D audio axes (X/width and Y/depth) using the tracking data from zactrack SMART. “With the combination of tracking and immersive audio, the image of the vocal coaches and instruments works extremely well, even in the front rows of the audience,” confirms Oliver Tschotow.
The 6K UNITED! tour was the first time that Melodus had used zactrack SMART for audio engineering. Ingrid Kreutzer from Melodus was responsible for setting up the system in the different arenas: “We used 11 anchors, most of which were permanently installed on the lowest array element of the line arrays and remained in place while being transported on the dollies.” A total of nine arrays were hung in the concert hall at 6K UNITED! – five for monitoring the choirs around the stage and four arrays for the audience sound. “As a result, we quickly had the system up and running in each new venue.”
Perfect symbiosis: zactrack and grandMA3 for precise light tracking
In addition to the audio tracking, the zactrack signals were also used for the follow-spot lighting of the musical director Prof. Fabian Sennholz and the two vocal coaches Lena and Beri, so they remained perfectly visible to the thousands of choir children in the hall. To achieve this, the pan/tilt values for the moving lights, which were calculated in zactrack SMART, were transmitted to the lighting system via sACN, along with the OSC signals for the audio. “It all ran over plug-and-play,” confirms Boris Kayser, who was responsible for the lighting design and operating on the grandMA3 full-size. In the end, a total of eight moving lights were automated to track the three people on the stage. Meanwhile, Kayser retained full control over all the fixtures via the grandMA3 interface and was able to run his cues using separate zactrack fixtures, optionally with or without tracking. In addition to the grandMA3 full-size, two grandMA3 processing units M were used for increased power and parameters, and a grandMA3 light stood at the ready as a backup console.
