Tony Birch has created an audio project that turns the auditorium of the Southbank Centre in London into a 3D instrument. Paul Milligan finds out more.
The career path of Tony Birch, the senior production technician at London arts venue Southbank Centre, is a familiar one he says with a smile, “just llike most sound engineers, I’m a failed musician who ended up doing sound for their friends’ bands.” After a stint working in live touring, he began freelancing at the Southbank Centre before becoming a permanent employee in 2018. And that was when the idea for Concrete Voids, which he says had been “kicking around his head for a while”, began to take shape.
Concrete Voids is a large-scale experimental audio project, which has its public debut next March, with a series of concerts featuring newly commissioned works by rapper and producer Lex Amor, electronic music producer and visual artist Jack Warne, viola da gamba player Liam Byrne and fiddle-player Cleek Schrey, and cellist Peter Gregson. Conceived and designed by Birch, Concrete Voids is a custom-built system of loudspeakers that turns the auditorium itself into a threedimensional instrument.
It consists of more than 80 speakers concealed within the chambers, tunnels and vents surrounding the Queen Elizabeth Hall auditorium. Using the spatial audio system TiMax panLab, sound sources can be moved and manipulated within the space, even by the artists as they perform. So where did the idea come from? It all stems from when the auditorium was closed for a two-year refurbishment in 2015. Birch was heavily involved in the sound aspect of the refurb, and changes made during that process sparked what is to become Concrete Voids.
“Originally, when the auditorium was built the fresh air came in from above and went through the vents and was then extracted underneath the auditorium. During the refurbishment the path of the air handling was reversed. Originally on the top of vents (3 rows of 14) there was ducting, when this was removed it opened up these massive spaces. That was the start of the idea of The Void.”
During the refurb lots of undiscovered nooks and crannies were found, when the pandemic hit Birch was working on live streaming from the venue, which gave him the opportunity to discover more about the acoustics of the auditorium. “I put microphones into some of these empty concrete spaces to capture the acoustic reverb that was generated from the band or orchestra on stage. Then my challenge to the person mixing it in post was don’t use plugins, just use what I’ve recorded. The result from that was insane because it’s actual real reverb rather than a plug-in, it initially sounds strange, but when you really start listening to it, it’s just completely different.”
At this point Birch knew this was an idea that sound engineers and musicians would think was cool but wouldn’t really have the same impact for an audience or for presenting work. “So I flipped it on its head and started thinking: what if, rather than capturing the sounds and the voids, the voids made the sounds? How would that feel in the auditorium? What happens if these spaces sing?” In 2022 Birch had finished working on a Claire Chase’s Density 2036 Commission which he says filled him with inspiration and led him to writing an email to his head of music with a ‘crazy idea’. “Her response was brilliant, she just said when can I hear it?”. Birch then built a small demo, with “a couple of plastic speakers” in some of the key points and it worked. That led to more stakeholders getting involved and the project was formally given a name in late 2022.
Birch also took inspiration from a Stockhausen (the German avant-garde composer) festival hosted previously at the venue. “In the score he would give you these crazy plans as to how to set up the sound system. The only way it could work was to do overnight rigging sessions to move all these speakers around and then do rehearsal during the day. I was doing all of the overnighters pointing speakers in really strange places, asking myself what we’re doing? But that was the start of the idea of going against the grain, this entire project is all about that, it’s essentially anti-acoustic.”
With a few months to go before the shows Birch is in the middle of R&D on the project, and says during that process, “there have been some wild surprises already, which I’m excited about.” Birch is keen for this to remain a research project for “as long as I possibly can”, adding “It’s a total unknown. It is an organic, living, breathing hall.”
Concrete heavy spaces are normally a sound engineer’s worst nightmare, yet in this project they are celebrated. How did Birch overcome this issue in what is a textbook example of Brutalist architectural? “The challenge is the space and its acoustically unkind surfaces but, that's the project’s point. When you talk about the world of immersive and spatial audio formats, those come with regimented rules and regulations to achieve consistency, everything has to be in the right place. I don't think this project has ripped that rulebook up, it simply ignored it completely”.
Concrete Voids has a main left and right hang in the auditorium, but everything else, all 80+ loudspeakers are all completely diffused. “Not one single loudspeaker points at you directly, everything has bounced off of a wall or gone through a vent. The whole project is the concrete. The very thing that you would call an obstacle is it.” Birch says the trick to understanding the whole project is “to understand that the building is an organic, living, breathing thing. If you do that, you’ll be fine. If you go in trying to achieve sonic perfection and turn up with real-time analysing microphones and software, you’ve got no chance.”
The Queen Elizabeth Hall was built in 1967, so how did he find a home for more than 80 speakers in a structure more than 55 years old? Birch describes the set-up, “There’s a loudspeaker on top of every single vent. We ended up custom making them because we had to be very mindful of our footprint to still maintain the air flow. We have 42 speakers in the roof, we’ve also got pairs of speakers that excite The Void themselves. That’s where all of that low energy can come from above. Underneath the auditorium, there’s six huge voids that are the length of the entire auditorium, perfect for sub-bass, so there’s loads of subs in each of these six spaces, but also because there’s grills underneath all of the chairs, the fresh air now comes from the bottom and goes up. That was the point where I realised that we could have full range sound underneath you, so there’s a big grid of full range speakers underneath the auditorium, people are floating on sound which is an amazing dynamic. Just to lock it in, so we are not just left with [audio] above and below, there’s a bunch of speakers that are also bouncing off the sidewalls.”
Does Birch see Concrete Voids as a long term project or is October 2025 the end of the line? “I think this is phase one. There are certainly discussions for its future post-October. I certainly want it to inhabit my brain for a while longer.”