WORLD-CLASS CONCERT ACOUSTICS
Koningin Elisabethzaal opts for wood and metal fabric in a shoe box
The Koningin Elisabethzaal in the northern Belgian seaport of Antwerp is unusual in every respect. Located at the heart of an architecturally charming city, structurally merged with a world-famous zoo, and boasting an immensely varied history as a concert hall, it transformed from an acoustic ugly duckling into a gleaming swan of aural experience. At the core of this metamorphosis is the design by the renowned American acoustician Larry Kirkegaard, who completely remodeled the hall acoustically. Golden metal fabric by GKD - Gebr. Kufferath AG (GKD) plays a key role in his concept. The woven texture really underlines the one-of-a-kind spatial experience in its use as large-scale cladding for ceiling, walls, and balustrades.
One of 65 participants in an international competition to redesign and remodel the Koningin Elisabethzaal, the consortium comprised of SimpsonHaugh Architects (London) and Kirkegaard Associates (Chicago) produced the winning design. Kirkegaard's ambitious concept, which employed structural and technical agility to aim for nothing less than a world-class standard for the new concert hall, played no small part in this success. The original hall was opened in 1897, served as a hospital ward during the First World War, morphed into a venue for boxing and wrestling matches during the Olympic Games a few years later, and was reopened in 1960 following major destruction in the Second World War. The fan-shaped design of this building, which was not intended to be used purely as a concert hall, contributed greatly to its poor acoustics, which achieved only six out of ten points on the rating scale. Plus, although it provided a stage, there were no rehearsal rooms for the orchestra and soloists. One aim of the new building was therefore to finally offer a home to the Antwerp Symphony Orchestra. The new Koningin Elisabethzaal is the centerpiece of the Elisabeth Center, which was also newly built as an ultramodern 25,000-square-meter conference center. When redesigning the concert hall, the planners decided to reduce its size in order to optimize the acoustics. This resulted in an enormous light-flooded foyer with atrium in the Elisabeth Center. Architect Ian Simpson embedded the new building into the historical complex in such a way that the art nouveau façades that had previously been hidden by the building were revealed once more and the old halls remained largely untouched. One of these halls, the Loos Hall , connects the new 2,000-square-meter concert hall with the historical part and also serves as the foyer of the Elisabeth Center. With its high stuccoed ceilings and rich marble decor, it provides a representative space for exhibitions and receptions. The new four-story building comprises various conference and meeting rooms for up to 1,900 participants, the concert hall with a capacity of 2,000 guests, extensive logistics facilities, VIP and catering areas, administrative offices, and soundproofed rehearsal rooms.
An acoustic embrace in a shoe box
The designers selected a shoe box shape for the concert hall, which classical music lovers deem to be a guarantee of optimum acoustics. This is aided by a perfectly balanced distance between the stage and the wall and an unusual seating arrangement in the parterre and the two galleries. Doing without a permanent apron also prevents a loss of sound. A curved wall means that the largest distance between the stage and audience seats is 30 meters, so that every guest feels part of what is happening on stage and can see and hear equally well from all seats. Movable reflectors clad in metal fabric and suspended from the ceiling as well as frames covered in the same fabric ensure that the sound is able to unfold throughout the entire hall. At the same time, the semitransparent membranes conceal the bare ceiling and the technical installations above. In designing the walls, Kirkegaard Associates chose a wave-shaped oak wainscoting. The cavities were filled with lava sand to prevent vibrations. With this construction, the acousticians drew on the sound experience of earlier concert halls, which employed arm-thick stone walls to reflect low-frequency sound back into the hall. As such, the walls and the rear wall of the stage in the Koningin Elisabethzaal form an acoustic embrace which ensures that the echo is not absorbed but is fully reflected to the stage.
Metal fabric for good sound
The same fabric that was used for the ceiling elements also covers the movable reflectors on the back wall of the stage: gold-colored powder-coated Alu 6010. For the ceiling and stage wall, GKD fitted a total of 204 frames, some of them wave-shaped, with 1,600 square meters of this fabric type. Four-meter-long and 2.50-meter-wide panels were fastened to the frames provided by the customer with thin stainless steel wires at intervals of ten centimeters. GKD also incorporated the cutouts for the lights exactly according to the specifications. A first for the weave specialists was that the entire construction consisting of frames and fabric was then coated in the desired shade of gold. This required special pretreatment in order to ensure homogeneous coloring of the components made from different materials - steel and aluminum. Prior to selecting the material, Kirkegaard Associates had carried out extensive tests on the GKD fabrics in order to achieve the best possible sound and space experience. As such, GKD was involved in the planning process with architects and acousticians from a very early stage. The decisive factor in opting for metal fabric was the acoustic neutrality. In addition, the exclusive look, flexibility, and robustness of the GKD fabrics corresponded to the ambitious design concept. That is why the fabric from GKD - Omega 1520 with gold-colored coated weft - was also chosen for the balustrades of the galleries. It fits flexibly to the bidirectionally curved corners of the balustrade and is also resistant to impact thanks to tensioning in the direction of the cable. When fitting the front and rear of the balustrade elements with 400 square meters of this fabric type, the curve needed to be followed exactly. GKD selected a slightly conical panel cut for this purpose in order to realize the radius by tracing a polygon.
The clever interaction between the design of the hall shape, ceiling, wall, and balustrade is what gives the new Koningin Elisabethzaal its excellent acoustics: with 9.3 out of 10 points on the rating scale, it is considered almost perfect. At the opening concert, Belgium's Queen Mathilde personally handed over the hall, which offers a world-class space and sound experience, to the public.