SOLUTIONS: GÄDDVIKEN REHEARSAL HALL, NACKA SWEDEN Good vibrations
A rehearsal and performance space used by Stockholm Royal Opera House is benefiting from flexible acoustics thanks to Europe’s first installation of Yamaha’s AFC3 acoustic conditioning system, writes Tom Bradbury
FOR EVERY sumptuously appointed orchestral or operatic venue, there is also a much more utilitarian rehearsal space. These invariably need to be big enough to accommodate a full production, so they are often sizable. The irony is that, while the venues have deliberately been designed with acoustics in mind, in many cases the rehearsal halls have not. Such is the case at Stockholm Royal Opera House. Opened in 1898, the 1,100- capacity venue stages opera and ballet and is home to one of the oldest orchestras in Europe, established in 1526. Productions are rehearsed at the Gäddviken Rehearsal Hall in the suburb of Nacka, where the 625sqm floor area and 17m ceiling height provide enough space to accommodate an orchestra, choir, soloists and complete opera set. To minimise unwanted reflections, the walls and ceiling had been treated with absorbent material, but this delivered an unnaturally dry sound for such a large space. With a reverb time of only 1.2 seconds when it was empty – less when it’s filled with a production – the Royal Opera Orchestra had long asked for improved acoustics and so Lars-Göran Ehn, the Royal Swedish Opera’s senior sound engineer, looked for a solution.
“The acoustic situation needed to be urgently addressed, but there was a lot to consider,” he says. “The room is used daily for staging and setting up full sets as required. However, in 2013 it is also being turned into a ‘black box’-style venue to allow opera performances without the restrictions of the auditorium in the Opera House. Changing from musical rehearsal to staging shows needs to be fast and manageable by a small group of people.” Initially the idea of a suspended ceiling and diffusion walls was discussed, but this proved impractical. “Suspending a solid ceiling would not work with our plans for creating a black box venue
Acoustics have been significantly improved in the rehearsal area
[INSTALLED]
AUDIO Yamaha AFC3-FIR core DSP units Yamaha AD8HR microphone preamplifiers Yamaha IPA8200 multichannel power amplifiers Yamaha PC6501N power amplifiers Yamaha IF2205 full-range speakers Yamaha IS1118 subwoofers 3-Zigma SD-C cardioid microphones Yamaha ICP1 control panel Yamaha CP4SW control panel SMT S-wing diffusor panels
with lighting trusses, flexible layouts and the ability to accommodate 8.5m-high sets,” says Ehn. “We tried a demountable ceiling, but needed a solution which was much more quickly adjustable and, in certain circumstances, would be possible to turn off the acoustics completely.” It was when Ehn visited a demonstration of Yamaha’s AFC3 system in Amsterdam that he realised it was the solution he had been looking for. AFC3, or Active Field Control, is an acoustic conditioning system that adjusts and enhances the acoustic characteristics of a space, while preserving its natural features. It achieves this by creating feedback loops using microphones and speakers located in the reverberant field of the room to ‘recycle’ the reverberant energy, thus extending the reverb time. “Active Field Control embodies Yamaha’s philosophy of ‘creating Kando together’ (meaning bringing together everyone in a shared audio experience – from the instrument maker through to the audience – all part of creating and enjoying better performances). As well as enhancing the audience listening experience, the fact that the AFC3 system improves the onstage sound
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helps musicians and singers to greater performing levels,” says Ron Bakker, systems marketing manager at Yamaha Commercial Audio Systems Europe, responsible for managing the introduction of AFC3 in Europe. “Yamaha has produced
systems to address this issue for over 20 years, but earlier systems were high in both cost and technical complexity, requiring a team of acoustic engineers from Yamaha Japan to tune them; they were only available for venues in Japan and the US. “However, modern DSP
processing has allowed the design and implementation process to be made much more cost efficient. Together with advanced automated functions – which mean local acousticians can participate in the tuning process – and the radically improved cost efficiency of DSP hardware, AFC3 systems are now within reach of much smaller concert
halls, auditoriums, theatres and churches. This is why AFC3 is now available in Europe, with Yamaha appointing several tuning partners to handle the system design and tuning phase of the projects.”
TRIAL RUN The AFC3 demonstration witnessed by Ehn took place in a small Amsterdam concert hall, using only 12 speakers with an improvised layout. But the potential for improving the acoustics at the Gäddviken hall was obvious. The AFC3 system’s speakers and microphones had to be placed at least 8.5m above the floor to allow full opera stage sets to be housed in the multipurpose space. Sixteen mobile SMT S-wing diffuser panels were employed as a complementary solution during orchestral rehearsals to support very early reflections. (This is unusual – for most installations with less
extraordinary height requirements, early reflections would be handled solely by the AFC3 system.) The AFC3 system was designed by Takayuki Watanabe from Yamaha’s Spatial Audio division in Japan, in close collaboration with Ehn and Mikael Collin, owner of Stockholm-based Audile Electroacoustics. Collin has a long working relationship with Yamaha and so was ideally placed to project-manage the installation on behalf of the Opera. Audile also managed the installation process to the design criteria specified by Yamaha. Suggestions by Ehn, such as adding four microphones to better cover the audience area when set up for performances, and the use of subwoofers to provide a warm reverberant response down to 40Hz, were included in the design. The completed system includes 44 Yamaha IF2205 full-range loudspeakers and four IS118 18in subs, all flown from the ceiling or mounted on the balcony. Twelve 3-Zigma SD-C cardioid microphones are mounted in three rows of four at 8.5m height – eight above the rehearsal area are used for the system’s rehearsal presets, or four above the front of the rehearsal area and four above the audience area for the concert presets. A 19in rack houses three
Forty-four Yamaha IF2205 full-range
loudspeakers and four
IS118 18in subs have been flown from the ceiling or mounted on the balcony
AFC3-FIR DSP units, two AD8HR A-D converters with microphone preamps, six IPA8200 power amplifiers to drive the full-range speakers and two PC6501N power amplifiers for the subs. A CP4SW control panel provides day-to-day control, its four
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