All clear in Dalian
Published: ASIA
When Dalian, in Liaoning Province, north east China, was chosen as one of the host cities for the 12th China National Games in 2013, plans were drawn up to provide it with a new cutting-edge sports stadium. Mr Wang Hai Wen, manager of Chinese distributor Top Plot’s Beijing branch, already had a working relationship with the audio project contractor, Dalian Wah Cheung Electronic Engineering Company, for the construction, and was introduced to the project director. As well as a main stadium, the Dalian City Sports Centre would comprise several smaller arenas to host different sports competing in the games.
A rigorous pre-selection phase got underway, encompassing acoustic design, technological features, worldwide references, system cost and brand support. Throughout this phase, Top Plot was supported and advised on system design options by Nexo Asia’s office, which also carried out a peer review at the end of the design process to double check that the designs submitted were correct.
‘The Top Plot Beijing team did an amazing job in designing the best combination of performance and price,’ explains Nicolas Kirsch, Nexo sales manager, Asia. ‘They put together an extremely cost-effective and lean system, fully optimising our NXAMP 4x4 amp platforms, and using the absolutely correct amount and types of cabinets at the right locations to achieve the SPL and STI (speech transmission index) where it counted. Hats off to them for the way they handled this.’
A phase of shoot-outs, interviews, meetings and visits by Nexo personnel duly followed. ‘To win such projects in China is a lengthy and arduous process where you have to give your absolute best at every step,’ explains Mr Kirsch. Eventually, Nexo systems were selected for the main stadium as well as the tennis and baseball arenas, based on cost/performance ratios, as well as references from previous international installations such as the Stade de France, which uses the same Geo systems as those proposed for Dalian.
‘The contractor, who is an extremely savvy engineer, holds Nexo in high esteem and was pleased with our proposals,’ says Mr Kirsch. ‘As this was a design and build project, there were no ‘target specs’. The client wanted to get the best possible results for the least possible cost. Obviously the intended usage of the venues was to be evaluated and the correct approach used. For example, the stadium is not only used for Dalian’s famous Super League football team, it is also the main venue for large cultural, community and international events. Therefore the emphasis on SPL, coverage and STI was greater for that venue. The tennis and baseball arenas are being used purely for those sports, so there were less demanding criteria for SPL and musicality, but more emphasis on STI and voice clarity.’
A Geo 12 line array system has been installed in the centre’s 60,000-seater main stadium, which hosted track, field and soccer events during the National Games, and is now the host stadium for Chinese Super League football team, Dalian Shide. With its gently undulating, colour-changing façade of 2,745 air pillows made from ETFE film, the stadium is the centre’s showpiece.
Inside the stadium, the seating area is covered from the top level down to the very front row by 18 Nexo Geo S12 arrays. Each array, positioned 30m to 35m apart, comprises three Geo S1210 and three GEO S1230 cabinets. A further 12 Nexo Alpha E-F full range cabinets are focused towards the playing field, with eight Nexo PS15-R2 high-powered speakers on standby for mobile applications, in conjunction with access panels installed at various points inside the stadium.
All Nexo cabinets are driven by Nexo NXAMP 4x4 powered TD controllers situated in equipment racks inside two giant video screens and in the control room. An EtherSound digital audio network has been installed for signal processing, and all of the NXAMP 4x4s are equipped with ES104 extension cards to receive audio signals from the network.
Top Plot also supplied the main stadium with a Yamaha PM5D digital mixing console and a Midas Verona analogue mixer for backup. The Yamaha PM5D is equipped with three Auvitran AVY16-ES100 cards to give access to and from 48 digital audio I/O channels of the EtherSound Network. Speaker equalisation is handled by three Yamaha DME24N digital mixing engines with Auvtran AVY16-ES100 EtherSound network extension cards. In addition, an Auvitran AVM500-ES100 is configured as a digital signal hub for zone distribution. Ten Auvitran AVRED-ES100s are used for long range EtherSound network to optical conversion, transmitting through dual optical fibres to the remote equipment room. The AVRED-ES100 also manages redundancy for the dual optical fibre transmissions.
The installation called for speaker cable lengths of up to 200m. As a result, more than 3,000m of Klotz 4mm LSCF440 four-wire speaker cable with 4.5 ohms of impedance added for every 1,000m was selected, with good results. Klotz SQ450, MY206, SCY2040, SCY2060, LY240 and PO122 cables were also used throughout the installation, with RC5SU EtherSound-certified network cable deployed for the EtherSound network. Additionally, four Klotz 312ATI GPO panels have been installed as breakout patch panels in the control room.
‘The main challenge for the stadium was to achieve internationally-acclaimed sound quality on a par with the best stadium sound worldwide, such as our Stade de France installation which reached as STI of 0.65 and SPL of 110dBA throughout,’ explains Mr Kirsch. ‘This of course had to be brought in on a budget acceptable by the Dalian government. The first step was to ensure the amps were fully loaded, as one NXAMP can power up to 12 cabinets of GEO S12s, three per channel. Then, looking at the stadium section and seating slope, we managed to fit six box clusters, with a combination of 10-degree and 30-degree modules. This provided very even distribution across the entire arena, keeping a bit more sound in the central and lower VIP seats. Where ticket prices are lower, a few decibels can be lost. Finally the horizontal placement was based on achieving the best overlap for smooth coverage and we ended up with 18 clusters, one at approximately every 20m. Shooting from a distance of 40m, our SPL target was 100dBA, under the IEC 268 standard, which is ‘loud’ already and suitable for 90 per cent of events, and within the FIFA and Olympics sound level specifications. To have raised the target another 2dB or 3dB would have brought the whole cost up massively, so this is where you have to draw the line between performance and budgets.’
The other two venues installed by Top Plot were the tennis and baseball arenas. The 110,000 sq-m tennis arena has seating for 10,000 people and consists of one main court, two semi-final courts, competition and practice courts. This arena, used, for all tennis events during the 12th China National Games 2013, now operates as a training base for the China National Tennis Team and will host tennis events for North Eastern China.
In the main court, the PA system was required to provide the highest SPL possible over the average spectator noise, and, once again, a Nexo Geo S12 system won out during a highly competitive tendering procedure. Four Geo S12 line arrays consisting of five Geo S1210 cabinets with 10-degree vertical inter-cabinet angles and a Geo S1230 with 30-degree vertical coverage have been installed as down-fills. The arrays are flown from either side of giant screens at both ends of the tennis stadium. Additionally, four PS15-R2s have been positioned on the ground of the court to cover some trouble spots. The system is powered by three NX AMP 4x4s. Top Plot also supplied a 32-channel Soundcraft GB4 analogue mixing console and a Yamaha DME24N for general equalisation. Again, Klotz cabling has been used through the installation.
The 36,000 sq-m, 3,000-seater baseball arena is one of just a few in China. The new arena is expected to help increase the popularity of the sport in China following its inclusion in the National Games, and as such its importance as part of the overall installation was significant.
The specifications for the baseball arena called for very high on-field coverage, and according to Top Plot, a Nexo Alpha system won this tender by performing way beyond expectations in terms of both clarity and SPL. The speakers are flown from the roof above the spectators’ seating area, transmitting sound in all directions to cover the entire space. Six Alpha E-M mid-high cabinets and two Alpha B1-18 bass units cover the playing field, while Alpha E-Ms have been installed into two side seating areas, with four Nexo PS15-R2s covering the central seating. Again, the entire system is driven by NXAMP 4x4s.
The results of the installation were pleasing to all concerned. ‘Our promise was to equal international high-end stadium intelligibility, but as we hadn’t received much info about the acoustics during the design process, we assumed a poor RT time, and designed accordingly, relying more on direct sound calculations than energy sum estimates,’ reflects Mr Kirsch. ‘We knew from experience that our design was good and would deliver, but not in an over-engineered way. We set an expected minimum STI of 0.55, which is a high standard for stadium work, not knowing how the stadium acoustics would be at the end of the day.’
However the team was pleasantly surprised. ‘As it turned out, the acoustics were better than expected, measuring around 4s RT60 in the empty stadium, and almost echo free,’ he continues. ‘After the contractor carried out a quick calibration, the system delivered to full expectations, giving strong musical presence and rich, clear vocal sound in all areas with truly good perceived intelligibility. The client’s expert team awarded the testing and commissioning certification with high honours.’
The stadium was immediately put to use on the China National Games, hosting the opening and closing ceremonies alongside the sporting activities. The result was a two-month test run for the system. Once this was over, Nexo sent in its own stadium specialist, Nicolas Poitrenaud from Paris, who had carried out testing and commissioning for many of Nexo’s Europeans stadiums, with Mr Kirsch travelling from Hong Kong to assist him.
‘Having been a consultant myself in the past, working with high-intelligibility PA systems, Nicolas and I made a good team and worked really fast, coming to decisions quickly,’ explains Mr Kirsch. ‘Focusing on the stadium as a priority, we carried out a set of basic tests and measurements, and found the system’s fundamentals were extremely good and stable and the speakers and amps were working perfectly. The system signals and networking, executed and programmed by engineer Mr Chan, from Top Plot’s Panyu office, were professional and flawless. The response in terms of SPL and coverage was never an issue, so we proceeded quickly to the calibration and fine-tuning exercise.
‘After critical listening, some vocal tests with wireless mics, a complete set of measurements in various selected locations and a set of EQ “touch ups” were presented to the users for their listening and choice. Those EQ points were purely meant to adapt the overall sound response curve to optimise the use of wireless microphones from within the stadium field, and give a better compromise between playback sound and live mic sound. These curves were drawn from Nicolas’ experience in tuning many other stadiums, to great results. A few of the EQ points were aimed at removing some low frequency overload, masking the clarity of mids and highs, and unleashing even more intelligibility and vocal transparency. The final measurements showed a very smooth 100dBA throughout the audience areas, with an average STI of 0.6 throughout the stadium. This was up to 0.72 in the crucial central VIP areas, dropping to just 0.54 in areas of low importance with less direct sound. We were really pleased; basically the system could achieve intelligibility results very close to our flagship SDF stadium, and within the client’s budget!’