20.09.07

Football comes home

AUTHOR: Inavate
Custom bracketry was supplied by Technique Engineering.

Four years in the making, English football finally has its new home. InAVate was given unprecedented, behind-the-scenes access to the new Wembley Stadium and Chris Fitzsimmons reports on the AV systems that play a crucial role in its operation.

6,500 Loudspeakers, 1000 audio channels, 390,000 pixels of LED display, 90,000 seats and one year late. There are plenty of superlatives and impressive statistics that can be used to describe the new Wembley Stadium, but none of those can quite prepare you for the experience of walking out pitch-side. There’s something about Wembley that stirs the soul of any English football fan and although the stands were empty, the pitch half-covered with protective plastic matting and the goal replaced by a touring stage, a visit to the site was still an incredible experience.

I was joined by three wise men who’ve spent a large portion of this century working on the project, and who gave me their unique insight into the Wembley epic. Mick Williams, has a history with Wembley, having been involved since the 1991 refurbishment of the original stadium’s sound system. James Hurst was responsible for taking the original system performance specification and turning it into a practical solution. The long-suffering Gerry Logue, Technical Projects Director of Live Business, the primary audio contractor, overcame armies of lawyers, threats of litigation and countless construction delays to deliver the project.

Sound check

From the point of view of an audio engineer, it is always much easier to work in a dedicated music venue. Many multi-purpose stadia; Wembley being no exception, are designed primarily for hosting sporting events and can prove challenging for music performance. Wembley has never been the ideal place for a stadium. It’s right in the middle of the residential borough of Brent where historically there have always been noise issues. The task then is to provide a fantastic sounding PA for match days and concerts, whilst keeping the sound firmly walled up inside the stadium bowl. In the old stadium prior to the installation of the bowl speaker system, all the sound had to be generated by the touring PA located at one end of the arena floor, with maybe a few delay towers. This led to severe restrictions on how many days each year the stadium could be used for live concerts. By using installed speakers to distribute the sound evenly throughout audience areas, this effect is now reduced.

The design process for the new system has been a very long one, as Mick Williams explained: “The 1991 upgrade was contracted just before Lord Justice Taylor’s report on the Hillsborough disaster was published. The thought processes behind the design in terms of the life safety considerations were essentially in line with the report, but much more attention had been paid to its performance and flexibility when not operating as an emergency evacuation system. The new design therefore incorporates elements of the previous design criteria for both music and life safety but not just in the bowl as previously, but delivered site wide – on a huge scale.

A key characteristic of the new Wembley sound system is its triple purpose, providing audio for life safety, public address and music / performance requirements. However in Williams’ view, it’s not this that makes it so innovative: “It might not be the biggest system in the world, but it’s got to be up there in terms of complexity. We’re talking about a number of multi-purpose systems in different areas; with individual zoning control, fully integrated with all inputs prioritised. The specific audio requirements of any area / areas cannot be decided in isolation. The bowl is a performance area, which sets it apart from the internal requirements of paging and so forth. It’s a big lump of the stadium you can deal with in one hit.

“This is opposed to the other parts of the site, where there could be a surprising number of completely separate functions going on in different spaces. This is a private area, this is a public area, this is back stage, this is staff only. Is this area private or public? How do we deal with routing audio for people in a restaurant, where they exit into a public area where there is a private function going on? Does that mean that staff need different announcements? What about those staff in the public area? These kind of issues dictate the requirement for such a flexible system.”

The vast majority of the 6,500 loudspeakers installed in the stadium were supplied by one manufacturer - EAW. Williams takes up the story again: “Whilst there would appear to be no shortage of loudspeakers available in the marketplace, we found remarkably few manufacturers whose product range would allow us the benefits of one-stop-shopping for the entire project. This has huge benefits from a supply-chain perspective. EAW were able to provide a complete, bespoke package of loudspeaker models to suit performance and aesthetic requirements in all areas throughout the stadium with production runs scheduled to suit installation timelines.”

Hurst’s involvement in the project began before a single brick was laid. He described his brief as follows. “Design the sound system for the new national stadium and make it excellent…. Unlike many projects, electroacoustic considerations were prioritised from the outset. We created a number of computer simulations to advise the architect about acoustic finishes and equipment. This work enabled detailed design to proceed; enabling selection and placement of all loudspeakers, sizing of amplifiers and routing / processing requirements, prior to going out to the industry to source the kit. The base design process sounds quite straightforward but tended to overlap procurement and installation timelines, with finishes and ceiling layouts in some areas not finalised until just before second fix!”

All systems go

The focal point of Wembley is the 90,000 seat stadium bowl. The star player here is EAWs KF750.

Hurst comments “There are a number of reasons behind this speaker choice. It was offered as part of a stadium wide loudspeaker package, which was commercially advantageous. The frequency response of the loudspeaker exceeded the specified criteria within a single enclosure, eliminating the need for separate low frequency enclosures. Structural loading was reduced as was steelwork / flyware etc. The visual impact of the relatively compact clusters is also less intrusive. The feedback we received from the industry was also favourable. Everyone has a stereo / preferred loudspeaker model, but this unit proved to be everyone’s second favourite.”

“The KF750 is a tried and tested solution, it’s fairly bullet proof and allows us a one size fits all solution, which we struggled to find else-where,” added Williams.

A total of 138 KF750Px-WP trapezoidal boxes (the W standing for Wembley) are hung in 54 clusters. The custom-designed structural flyware and cluster management was manufactured by Technique Engineering. The speaker connectors themselves are also a non-standard solution. Rather than hardwiring tails into an IP68-rated connector or junction box, the W model of the KF750Px-WP is fitted with a Bulgin submersible connector. This meant that the riggers, already coping with being suspended high over the pitch to hang the speakers, had much less to worry about when connecting them up, which in turn reduced the Health and Safety concerns, and simplifies future maintenance procedures.

Balcony under-fills are provided by a total of 180 pieces of EAW UB22I full range units, 90 on each level. Amplification throughout is provided by a total of 313 Crown CTs series amplifiers of various power ratings across the whole range.

A major difference between the new and the old system is the way it interacts with touring systems. In the past, there was an option to either hook the touring system in to the house system or not. Now, if you want to fill the top tier of 30,000 seats, there’s no choice. Hurst explained: “We always knew from day one when we did design calculations and predictions using modelling software, that the biggest arrays available at that time wouldn’t cover the top terrace at all. For the people sitting in those seats, they are essentially listening only to the house system. The rental system is kind of like an effect – it’s like reverb.”

“It’s a learning curve for engineers and system people coming in with their productions” added Williams “The idea of someone coming up to you with an XLR in his hand and saying ‘gissa feed into the house PA, will you?’ is not likely to make it into the list of things you most want to hear when you turn up at a venue with a few trucks full of this year’s shiny new boxes. However, it really shouldn’t be that scary: Leave your pre-conceptions on the bus, brush up on your O-level trigonometry and laws of physics, and give it a listen. If you make any arbitrary decisions about how you want to use it to subtly ‘augment’ your system, if you decide that you just need a little HF lift and your system will do the rest, then 30,000 people are going to go home feeling that they’ve just spent the last few hours with their nose pushed up against the window watching the people inside have a good time, while they were stuck outside in the cold.

Walking around Wembley’s internal spaces it’s clear that the architecture presented significant challenges to the design team. Hurst remarked: “The project was so big, that we basically decided to innovate as little as possible.” The main atrium is a multi-floor space with a 15 metre high ceiling and one wall almost completely glass.
To successfully deliver audio to this huge reverberant space, Duran Audio Intellivox column speakers are fitted to the one available wall. These digitally steerable loudspeaker arrays give increased intelligibility and consistent SPL throughout the atrium.
The ceiling in one of the larger dining rooms has all the services visible and yet integrated with beautiful curved kite structures. The effect is visually stunning, but proved incredibly awkward to incorporate the installation of 50 large trapezoidal EAW VR21 loudspeakers.

The primary ceiling speaker throughout the site is EAW’s CIS400. It’s found in the restaurant areas and on the concourses. James Hurst selected the two-way speaker for its sound quality, which is further enhanced by the acoustic treatment throughout the building.

The core technology is Peavey’s Nion digital sound processing and routing system. At the most basic level it allows audio from any source to be routed to any zone in the site, be that a restaurant or a section of seating in the stands. Programming the system proved to be the hardest part of delivering the audio solution. As with any complex system, the more elements there are, the more things there are to go wrong, and to finally hunt down all the bugs, and solve the problems took input from Peavey, Peak Audio and specialist audio systems programmer Martin Barbour.

Background music can be supplied from a central server to each of the individually pageable 319 PA zones via the Revolution digital music network supplied by C-Burn Systems Ltd. This connects and coordinates the 17 hard disc music players situated in the control room and 16 bars and restaurants. These local Revolution units enable each area to have its own musical style and character in line with how it is used on an event by event basis. Each player can be used interactively as a kind of digital DJ or will it work automatically, intelligently selecting songs from the server to suit the time of day and needs of the area. Paging and radio mics for stadium staff are also provided in each of the 16 areas.

Adam Smith- managing director of C-burn explains, "The Revolution Digital Music Network allows Wembley to do everything from playing each team's pre-match favourites in the changing rooms and Prince Harry's beloved Hip-Hop in the Royal box whilst ensuring the music in the public venues is exactly suited to the day. C-burn provides specific play lists for individual events to get the ambience just right and, to ensure the music stays fresh, C-burn updates the network every month with a raft of new hits and old favourites”.

And then, of course, there’s a copper-based, analogue back-up ‘all-call’ system. Formula Sound’s Guardian CX10 was specially developed by the company for Wembley, but has now made it into the standard product range. 100 of the 10 channel units override any existing audio signal individually into the 1000-odd inputs to the electro-acoustic end of the system with the emergency channel.

Acoustic treatments have played a key part in the system design at the new stadium. The initial calculations that Hurst did from the architectural drawings of the atrium indicated a mid-band reverberation time of around12 seconds. Careful selection and placement of acoustic finishes has reduced that to approximately 3 seconds with excellent intelligibility afforded.
Acoustic finishes are also located on concourses and restaurants, reducing reverberation times ensuring excellent clarity and intelligibility.

Acoustic considerations were also key within the stadium bowl. The glazed front faces of the boxes are all offset by 5º to break up reflections. The leading edges of the balconies are treated with a 50mm thick coating of rockwool mineral wool behind perforated facia panels. The rear of the roof is also treated with a similar finish to minimise the strength of late reflections at seats in the rear of the upper stands.

Wembley does nothing by halves, including its commitment to disabled visitors. The UK’s recently updated Disability Discrimination Act (DDA) requires that the stadium can offer an experience to disabled visitors equal to that enjoyed by able-bodied ones. For the hard of hearing, and those with poor sight, there is, in effect, an industry-standard UHF in-ear monitoring system supplied by Sennheiser, utilising the 300Series IEM transmitter, elevated to about one watt by a bespoke UHF amplifier in one of the racks in the roof gantry, with a single 5000 Series antenna hanging below the catwalk like a black goldfish bowl. Disabled people have almost invariably had to put up with relatively expensive, small-scale production equipment to address their specialist needs. This commentary system allows standard product from an international manufacturer, built with the resulting economies of scale, to address the needs of a minority group. EK1038 Guided Tour receivers, almost identical to the Sennheiser IEM belt-packs, except in mono, are available from information booths, together with either headphones or a neck-worn induction loop, enabling users to receive an FM quality dedicated commentary for any sporting events. As part of the Stadium PA system, it naturally allows the same priority-structured information and emergency announcements as any other zone in the complex.

Whilst the sound system really is the star of the AV show at Wembley, much of it might well go unnoticed by the fans, although they may spot the 54 very elegant clusters of speakers in the bowl. One might argue that that’s as it should be. What certainly won’t go unnoticed are the two large LED screens located behind each goal. Each is 13.5m wide by 7m high and consists of 180 units of Barco’s Slite 22 Outdoor LED product. The LED pitch is 22mm. It is driven by Barco’s D320 digitizer, which can act as a four-way source switcher. Controlling the solution is the company’s Sports Box software and hardware package, this delivers on screen content such as the scores and substitution information.

Stade de nightmare?

Whilst it’s easy to wax lyrical about the wonders of the technology, the quality of the PA and the beauty of the finished article, it’s unfair to those involved in the project not to highlight the extreme difficulties that had to be overcome simply to get the project finished. A seven-month installation job became a two-and-a-half year slog for Logue and his team, and he recalls days when there were more lawyers on sight than workmen.

Many column inches have been written in the building press since it became clear there were problems at Wembley. However, the opinions expressed by many involved in the AV-side of the project indicate the fundamental lessons that are still yet to be learned about the relationship between civil engineering and technical specialists on big projects such as this.

However traumatic the experience may have been, those involved are justifiably proud of the outcome. James Hurst concluded: “It’s got a sound track hasn’t it. It was the design intent from day one that this would not just be about music in the bowl but it’s in the bars and restaurants, in the concourses, outside, as you approach, as you walk through the turnstiles, as you leave – a music stadium. That was the idea and it’s working well.”