The Alfried-Krupp-Saal at Philharmonie Essen in western Germany, renowned for its acoustics and for being home to the Essen Philharmonic Orchestra, has been outfitted with a new sound reinforcement system headed by L-Acoustics Kara II loudspeakers as well as an acoustic overhaul to support programming that also includes pop, rock and jazz concerts.
Acoustic consultant Müller-BBM Building Solutions had performed all the acoustic planning for a renovation two decades ago of the 2,000-seat hall, and was again approached by Philharmonie Essen in 2019 as the choice for the new design. Previous projects included extensive architectural renovation, such as the addition of an 18-ton adjustable polygonal panel above the stage, designed to improve the auditory experience for both musicians and audience by optimizing the hall’s reverberation characteristics to help optimize the room’s acoustics for live orchestral works.
“The previous system had worked very well, but with the evolving music program, there was a need for a little more power,” says Müller-BBM’s Harald Frisch, who planned and designed the hall’s previous system and is now responsible for its current loudspeaker and electroacoustic design. “We knew the room acoustics very well. We even had the models from the first planning, which we used to check to confirm if they were still as close to reality as possible before planning the new loudspeaker system.”
Frisch and his team organized a blind loudspeaker evaluation with an audience of around 20 people, using an L-Acoustics system as well as two systems of competitors. Since the original system was self-powered, two separate technical specifications were drawn up: one self-powered, and one using external amplifiers. When costs were compared, L-Acoustics proved preferable in terms of audio quality while also being more cost-effective.
One of the challenges Müller-BBM faced was the venue’s side galleries, which had not been adequately covered with the previous system. “To address this, we used larger arrays for the side galleries rather than delays,” explains Frisch. “While delays may be the usual choice, it has the unhappy side-effect of localizing sound away from the stage for the gallery audiences. We wanted to have a sound source coming from the stage that was strong enough to reach the galleries and localize sound from the stage, no matter where the audience is seated.”
Since the venue is primarily a concert hall for classical music, all arrays must be raised up to the roof during classical concerts, making the sound reinforcement system invisible. “This created some rigging and cabling challenges to solve,” Frisch says, adding that the benefits were worth the effort.
“We also included a delay line for the gallery opposite the stage to prevent late reflections from the rear wall,” he continues. “With the new system, the main balcony on the opposite side of the stage only gets a little impulse from the main system to create an acoustical localization towards the stage. A powerful delay system is installed to fully cover the balcony with proper sound pressure level.”
The new Kara II-based system was supplied, installed, and commissioned by Amptown System Company GmbH, an L-Acoustics Certified Partner Integrator in Germany. Amptown project manager Michael Klötzer notes, “The basic design was done by Martin Rode, senior application project engineer at L-Acoustics, who collaborated with the Müller-BBM team to achieve the final outcome.”
Rode explains, “Part of the specification was to improve the coverage in the upper balcony, which was always tricky with the old system. Since the horizontal dispersion of Kara II is adjustable, it’s possible to tune that to the shape of the room. We set the upper cabinets in the main arrays to 90 degrees, and that gave us a great result. This is unique to Kara II, and it’s given us much greater clarity than other systems can achieve.”
The audience area is covered by left/center/right arrays of Kara II arrays comprising 12 cabinets left and right, with eight Kara II in the center. Four KS21 subs per side in cardioid configuration provide low-frequency energy at each side of the stage with nine compact 5XT spread across the stage lip to provide front-fill while keeping sight lines clear. A pair of A10 — one Wide, one Focus — sit atop the KS21, allowing the audience to localize vocal content at stage level.
The design throughout the hall is effectively a distributed system covering 360 degrees. Arrays of three Kara II cabinets per side cover the upper side balconies, once again using the adjustable dispersion — two of the enclosures are trimmed to a very narrow horizontal dispersion of 70 degrees while the lowest cabinet is set to 90 degrees to cover the middle balcony. The choir balconies, above and behind the stage, are served by four arrays of A10 Wide: the two inner consisting of three A10 Wide and the two outer arrays counting one each of A10 Focus and Wide.
Additionally, the rear balcony area at the side behind the Kara II arrays is covered by an A10 Wide for the upper balcony and two A10 Wide per side for the lower balcony. “Although the main system covered those areas, the additional speakers gave us a little more energy and a bit of freshness there,” Rode notes.
Calibration was performed using a P1 processor in combination with M1 software, and despite having up to 122 separate measurements to analyze, the process only took around two hours as the M1 measurement sequence handles up to four mics at the same time.
Rode reports that the venue’s team has been fascinated with the homogeneity achieved: “The sound image is constant with the acoustic orientation always towards the stage. Regardless of where you are in the room, the sound image is always in the right place.”
