Located in a heavily populated residential area, the new 300-capacity Club SUB was challenged with providing an extremely loud and clear low-frequency sound solution, while maintaining acoustic isolation.

“The owners’ goal was to achieve a similar sound performance as it had in the Grelle Forelle Club in Vienna," commented Lambda Labs’ director Steffen Kroschel. "Given the concerns of local residents, when Mr. Sauter [project manager] surveyed the building, with its tube like architecture, the abstract idea of a ‘vibrating wall’ became more logical.”

Lambda Labs’ Richard Nell supported the concept with simulation data, parameters and measurements — applying his knowledge of high performance concrete ‘closed box’ enclosures and amping. The drivers were developed especially for this application, going through 10 prototype stages, while the club owners helped with casting the concrete loudspeaker enclosures.

For the rear wall, behind the 6 x 5 metre stage, 400 kg special concrete blocks were cast and set into a 6 x 3 metre wall, using 13 tons of heavy concrete and a further 35 tons for the foundation.

“It was extremely difficult to handle these enclosures with small forklift trucks and build the 50 cm deep low frequency absorber,” recalls Steffen. “Behind the wall is sand, and under the wall, Mr. Sauter chose material that is used for highway construction.”

Each concrete block serves as loudspeaker enclosure with pressure-resistant rear chamber which implements the perfect impulse response of a ‘closed-box’ design and maximizes the radiation resistance of the woofers through the acoustically hard surface. A self-enveloped 15-inch speaker was produced and adapted to the unusual demands of this project. The single chassis are designed to act together like one single swinging wall — in a similar principle to a piston in a cylinder.

Steffen explains the concept further. “A perfect plane wave is created in the interior of the club, which naturally moves along the side walls and doesn’t induce any room modes. The rear of the main floor was converted into a single bass trap to absorb the incoming wave. The SUB thereby achieves an acoustical result that could never be reached even outdoors.”

Yet to make this all work, each driver needed to be powered by its own dedicated amplifier.

“As we have been using Powersoft amplifiers in our regular self-powered loudspeakers for four years, it was obvious to choose the company again for this project as we have a lot of experience with their modules, such as the Digimod 1500, which we use successfully in our subwoofer product MF-15A and our full range enclosure TX-3A,” continues Steffen.

The 32 Lambda Labs OEM CX 15-inch ultra-long excursion drivers, with ± 25mm linear excursion capability set in housings made from special concrete. Each is driven by 800 Watt amplifying modules, with the maximum desired SPL reached at an excursion of only ±3mm. Therefore the ‘Wall of Bass manages with only 500 Watt peak music power during operation.

In addition, special mid-high speakers generate a cylinder wave for longer throw and less room reflections while the DJ reference sound is provided by CX-1A and CX-3A self-powered monitors with Powersoft D-Cell modules.

Summing up, Steffen Kroschel says that everyone who has played through the system has been hugely impressed. “For some it has changed their awareness of music.”

“Although we have not been able to find movie soundtracks with lower frequency response than 20 Hz, during our live presentations of the ‘Wall of Bass’, we play an original recording of a Challenger rocket launch, to give a natural idea of the breathtaking force. Another show element was to generate some sine waves down to 7Hz, demonstrating this outstanding response by also making the acoustic waves visible with smoke.”

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