A Very Complex Audio Environment

Design Process
We began designing the system 18 months prior to the event. Our goal was to provide the technical team with weight loadings, power requirements and system layouts for coordination, while also giving the creative team an indication of sightlines and audience points of view.

When geometry allows, I design coverage of the upper bowl with a flown system and the lower bowl with a stacked system, as this allows me to maintain localization for the upper and lower bowl audiences while minimizing overlap.

My design process begins with a study of the venue in CAD to gain a detailed understanding of the geometry. I begin with a plan of the field of play and lower bowl to study the horizontal plane and determine an approximate number of ground stacked arrays required to deliver consistent coverage in the front few rows.

As a starting point, I always leave at least 10 meters between the stacked arrays and the first row of the audience since it provides a more consistent SPL in the vertical plane. Using the simple inverse square attenuation over distance, the first 10 m equates to -20 dB, the following 20 m (typical depth of a stadium lower bowl) sits within a 10 dB SPL window. This window is further reduced in the array design using angles.

I also stick to the ‘if you can’t see it, you can’t hear it’ rule, ensuring every row has a direct line of sight to the loudspeaker element with which they are on axis.

Once this distance has been determined, the number of ground stacked arrays required is a simple exercise in CAD based on a generic horizontal -6 dB angle of 110 degrees. The azimuth is set so that each array is pointing perpendicular to the line of the front row. The number of loudspeakers in each ground stack is determined by audience sightlines to the performance area, which is often only 1500 mm, just enough space for four dual 12-inch line-source elements.

At left, the K2/SB28 flown systems deployed for the Olympic opening and closing ceremonies (highlighted in yellow & represented with the roof arch). At right, the K2/SB28 distributed ground stacked systems deployed for the Olympic opening and closing ceremonies (highlighted in yellow).

After doing this, I can focus on the upper bowl in the horizontal plane. I start with an upper bowl array on the same X/Y coordinates as the ground stacks and adjust the height so that the top of the array is a couple of meters above the back row. This approach dictates that there be the same quantity of flown arrays as ground stacks, unless the upper bowl is not a full oval, in which case unrequired arrays are deleted from the design.

The azimuth of each array is adjusted to point perpendicular to the line of the back row, which is hopefully similar to the azimuth of the corresponding ground stacks. Then it is shifted along its vector towards the audience to reduce the overlap with adjacent arrays and ideally to have a consistent throw distance for each.

Where possible, I aim to make the relationship between each array and each corresponding coverage area as consistent as possible by matching throw distance, trim height, vertical angle of incidence and array length. This approach delivers a more consistent response and simplifies the tuning of the system.

Our flown system was relatively straightforward, except the corners of the upper bowl which were problematic due to the proximity of the loudspeaker arrays to the main roof arch. This area was also populated with lighting truss and fixtures, so the final trim heights were left to be decided onsite during installation. With a first draft design in hand, I could turn my energy to considering suitable products for the project.

Choosing Loudspeakers
I quickly zeroed in on three different loudspeaker options from three different manufacturers, based on criteria including rental availability and a combination of best case and worst-case scenarios for system power and weight requirements. Over the next few months I refined the design and a few months before the Sochi audio tender was due, I visited L-Acoustics on the way back from meetings in Moscow, and the team there was very excited to introduce me to a working prototype of what was on its way to becoming K2.

They followed up by sending me a Soundvision Beta software with the new product that allowed me to model designs that were lighter, more flexible and that could use the same product in both flown and stacked arrays.

Soundvision showed me that the K2 combination of Panflex variable horizontal dispersion, and up to 10-degree angles between elements in the vertical plane would deliver a more consistent response in the vertical plane with fewer elements, as well as fewer damaging overlaps in the horizontal plane – a boon for speech intelligibility. In addition, the high SPL and extended bandwidth offered by K2 (3 dB below K1 and same bandwidth) was also the right fit for the creative intent of the ceremonies and the scale of the event.

Zoom view of a couple of flown K2 & SB28 arrays.

Rapidly, it was clear that K2 is the only product that can deliver the differing horizontal dispersion requirements for both the ground stacked and flown arrays. This also allowed me to determine the maximum quantity I needed, without committing to a final design.

For this reason, K2 was specified and we began searching for vendors. Italy’s Agora secured the contract and the pressure was on L-Acoustics to deliver 230 K2s, plus a pile of other products required by the design, by the deadline.

Ultimately I developed two designs, one for the Olympics Games Ceremonies that split coverage of upper and lower bowls between flown and stacked systems, and a second one where we flew everything as the Paralympic Games Ceremonies required the field to be clear of equipment for athlete seating.

Olympics Configuration Flown System
For the Olympics opening and closing ceremonies, we flew 16 arrays—eight per side. Each array was suspended from a truss with nine K2s at one end and four SB28s at the other. The four corner arrays were K2 only.

We flew our SB28s 2750 mm behind the K2s to allow room for the extra four K2 that would be added for the Paralympics ceremonies. The arrays were trimmed to match the height of the back row of audience, keeping sight angles at zero degrees.

Adjacent K2 70-degree array respective coverage represented using Soundvision Coverage mode. Note that filled Impact Points represent the usable coverage (-3 dB from axis) and are used as a reference when adding adjacent sources.

The same adjacent K2 arrays combined coverage represented using Soundvision Mapping mode.

The consistent throw distances, discussed earlier, were optimized for K2’s 70-degree horizontal dispersion using the Panflex adjustable directivity that delivered consistent overlap between adjacent to balance intelligibility with a spatial audience experience.

On the vertical plane, K2 WST true line source behavior and vertical flex allowed me to achieve the desired coverage and SPL distribution with few enclosures with the insurance that K2’s high SPL capabilities also assured me that I was not going to run out of steam for the show.

A single K2 array vertical coverage and SPL consistency. Note that SPL deviation is within +/- 1 dB.

Olympics Configuration Stacked System
The ground stacks were distributed around the perimeter of the show-deck for lower bowl coverage. The area between the show-deck and the front row used for technical equipment and cast movement provided just the right distance for us to deliver even coverage from front to back. We created a horizontal line of three SB28s, which gave us low-end pattern control in the horizontal plane.

Zoom view of a ground stacked K2 & SB28 array.

Four K2s were placed on top of the center SB28 with the bottom element set to 110° and powered individually and the top three set to 70 degrees and powered as a group, thus providing coverage of the same horizontal width of the seating bowl despite the 18 meter difference in throw distances.

On the vertical plane, the increased sensitivity of the 70 degrees upper elements offsets the greater throw distance and allows for nearly no SPL differences from front to back.

A single ground stacked K2 array coverage represented using Soundvision Coverage mode with bottom K2 set at 110° and upper K2 at 70 degrees.

A single K2 array vertical coverage and SPL consistency. Note that SPL deviation is within +/- 1 dB.

The benefits of this setup was massive in terms of protecting intelligibility and providing a more consistent audience experience throughout the lower bowl. The ground stacked system was augmented with ARCS II and 12XT delays to provide additional coverage of temporary seating stands on the concourse level at the north and south ends of the stadium.

Paralympics Configuration Flown System
The stage design for the Paralympic games ceremonies placed the athletes in the area between the showdeck and the front row, so we covered the lower bowl with flown arrays only, adding small floor-standing loudspeakers to cover the athletes.

There is an extremely short transition time between the Olympics closing ceremony and the Paralympic games opening ceremony, and a whole lot to accomplish in this short time. I optimized the design of the flown arrays for the transition by adding four K2s from each ground stack to the flown arrays, taking them from nine elements to 13. The angles in the top nine elements did not require modification because the 10-degree inter-element angle of K2 allowed us to provide coverage down to the front row. In addition, two of the three ground-stacked subs were added to each flown SB28 array taking them from four to six elements.

At left, a zoom view of a flown K2 & SB28 array used for the Paralympic opening and closing ceremonies. At right, coverage area of a single flown array represented using Soundvision Mapping mode.

Vertical coverage and SPL consistency of a single flown array. SPL deviation is within +/- 1 dB.

The loudspeaker system for the Paralympic athletes consisted of 64 8XT loudspeakers on custom floor-mounted stands and time-aligned with the flown system. Additional SB28 subs were added to warm up the athletes’ seating area.

VIP Systems
The VIP tribune on the west side of the stadium, just below the control rooms, welcomed world leaders. The layout of this area was not known until very late so coverage from our main systems was unclear. I designed a VIP-specific delay system of 30 5XTs to reinforce mid and high frequencies to the VIPs. A special stereo surround system was created that allowed us to deliver them surround audio from the many video packages.

Special Systems
A special dV-DOSC was used for a train sound effect at the southern end of the stadium. During the closing ceremonies it became a PA for the Russian DJ in the center of the stage and again for the Paralympic Games opening and closing ceremonies, the system was used at the northern end of the stadium for a ship sound effect.

Systems Preparation
The loudspeaker system needed to be installed the moment it arrived in Sochi making complete testing prior to shipping essential. Agora received its K2 in time for complete factory testing, including impulse response measurements, slow sine sweep to check for rattles, rigging inspection, connector inspection and inspection of the fins. I created a shared spreadsheet for Agora’s loudspeaker system engineer to track and record each test per element.

All systems were prepared to Agora’s impeccable standards and were ready to ship to Sochi ahead of time. Transportation into Sochi was no small feat as there was a monstrous backlog of arrivals in the port. Our system arrived late, with just enough time to get the work done.

Systems Installation
Because the K2s weigh in at only 56kg, they are easy to maneuver and the installation process went fast. Using the trusses to separate the K2 from the SB28s made for very consistent offsets and also provided a structure to roll the 200 kg cable loom onto. All of the ground-stacked LA-Rak and control nodes were installed first so that as loudspeakers were added, we were able to test each array as it was installed.

My control system design uses a four core optical fiber cable with two cores used for audio signal transport on Optocore hardware and the other two used to create a meshed Ethernet network for control of products such as Shure wireless receivers, Lake Processors and LA8 amplifiers as well as to distribute internet access to the various audio control areas.

The LA-Raks were connected to the control network very early on to allow our audio technical manager to configure all the amplifiers and the groups in LA Network Manager well before the loudspeakers were connected.

The final step of the installation process was to install the front of house mixing consoles and outboard equipment. A dual-redundant pair of DiGiCo SD7 mixing consoles was used as well as dual-redundant pairs of TC M6000 effects processors, SPL Vitalizers, a pile of Emperical Labs Distressors and Drawmer S3 multiband compressors. Once FOH control was up and running the commissioning process began.

Systems Testing
With the amount of preparation needed, the site was operating day and night and our daily tuning took place from 5 am to 9 am – the coldest part of the day, which made keeping warm the most difficult part of commissioning! We used a combination of Rational Acoustics Smaart 7 and IMFG EASERA Systune, with Lectrosonics wireless links and Earthworks M30 microphones.

The difference in temperature between sunrise and show time was significant so the focus was on confirming system coverage, identifying any gaps filtering out the obvious bumps and working on time alignment of the different parts.

Checking Coverage
Clear and attainable goals are the key to making the most of the commissioning period. Day one and two were all about putting on music and walking the venue, occasionally swapping the music for pink noise or a wireless microphone. It is important to identify coverage gaps early, because moving arrays or installing additional loudspeakers requires coordination with other services. It’s also an opportunity to adjust the tilt of pan of each array to ensure the installed location matches the model.

Testing & Commissioning The Upper Bowl
Once I am satisfied with system coverage, I focus on vertical plane consistency, taking multiple measurements in the vertical plane on axis of a single array. This allows me to understand sound pressure level and air absorption differences within vertical coverage, as well as to assess spectral balance within each array.

This process also informs how best to group parts of adjacent arrays for treatment during the rehearsal process. For example, the centre four arrays on each side of the stadium had the longest throw distance, with very similar measurements in the back rows. The top three elements of= each array, all of which had the same throw distance to the back row, were placed in a group for air compensation treatment.

Soundvision mapping of the upper bowl system.

Sochi 2014 was the first time K2 had been deployed on a large scale and we spent the time required to fully exploit the array morphing tool to sculpt the frequency contour of each array to our needs.

The low frequency power of K2 is surprising—an array of nine K2 has a weight and power to it that I didn’t expect—with a very warm, tight and big bass sound that transitions perfectly to the SB28s. With over 200 K2s in the venue, the room reacted to the bass power and the Zoom Factor was finally fixed at 0.63 for both the flown and ground-stacked arrays. The summation between the flown K2s and SB28s is also measured and adjusted for each array during this
process.

In the high frequencies, the three FIR filters in LA Network Manager are perfectly placed to do exactly what both the measurement and subjective experience require. The width and the shoulders of these filters are perfectly shaped to take care of balancing the HF.

I also made use of the air compensation filter, which does exactly what you would expect. Each nine-element array was amplified in groups of three, allowing three zones of air compensation per array. On average, +3 dB of air compensation was used in the top zone of each array, +1.5 dB on the middle zone and none on the bottom zone.

Each of the flown arrays was treated individually to deliver a consistent listening experience throughout the entire upper bowl with a generic system tuning.

And The Lower Bowl
The lower bowl presented different challenges. A typical array had three subs with four K2 stacked on top of the center sub, but a few arrays were tweaked due to sightlines. Some had K2 stacked in front of the center sub and some had only two subs. These differences meant every array had to be measured to a target; the key was determining the right target. We chose to measure against the typical layout of four K2s on top of three SB28s.

Soundvision mapping of the lower bowl system.

As might be expected on such a shallow angle of incidence, subtle changes make significant differences. I used the modeling process to give me a few alternatives that we then used for direct comparison. Each of the three options were measured for vertical consistency and tonal balance. Once the best was determined, the summation to the SB28s was finalized and the angles were deployed throughout the system. Each array was then individually measured in multiple locations to ensure consistency with the target.

Subjective Tuning
The rehearsal process begins with a loudspeaker system that is balanced and time-aligned but is yet to be tuned to taste. This is a process that continues right up until our final dress rehearsal with a full house. Final tuning is a collaboration between FOH mix engineer Richard Sharratt, audio consultant Bobby Aitken and myself. Ultimately the system performed brilliantly, consistently and predictably.

How it looked during the opening ceremonies for the Olympics.

The usefulness of Soundvision cannot be overstated, especially in an environment of such high risk and high expectations. The venue was not complete until very late and didn’t exactly match the plans, the acoustic environment was challenging and events of this scale are expected to be an amazing experience. I relied heavily on Soundvision to provide me with direct field performance that I could bank on. The software took away the majority of the design risk and was used as part of the decision making process for every change to the loudspeaker system design.

The Ceremonies
All four ceremonies were full houses with really loud, engaged and involved audiences. We were planning to run the Opening Ceremony at around 108 dBA peak, based on our dress rehearsals, but with our noisy audience, we increased 4-5 dB throughout the show.

The view inside of Fisht Stadium from front of house during the Olympics.

The system reacted well to the increase, the subs ran into limiters on a couple of occasions during low frequency sound effects and the dV-DOSC arrays used for the train sound effect were nearly turned inside out. We had nothing but positive comments from the production team and audience. I had a few colleagues who have spent plenty of time in front of big loudspeaker systems in stadia and they too were very impressed with the performance of the system, especially in such a difficult acoustic environment.

The Audio Team
Scott Willsallen, audio director and sound designer
Bobby Aitken, audio consultant
Justin Arthur, audio technical manager
Richard Sharratt, front of house mix engineer
Andy Rose, broadcast mix engineer
Steve Logan, replay systems operator
Luis Miranda, assistant replay operator
Griff Hewis, broadcast Atmos mix engineer

The Agora Team
Giulio Rovelli, project manager
Giulia Dagradi, assistant project manager
Angelo Camporese, crew chief
Daniele Tramontani, senior systems engineer
Lorenzo Tommansini, broadcast systems engineer
Umberto Polidori, monitor mix engineer
Andrea Tesini, RF systems engineer
Ian Baldwin, RF systems consultant
Luca Nobilini, field systems engineer
Stefano Guidoni, field systems engineer
Fabrizio De Amicis, loudspeaker systems engineer

Loudspeakers & System Racks
230 x K2, 98 x SB28, 16 x ARCS II, 24 x dV-DOSC, 4 x dV-SUB, 20 x 12XT, 72 x 8XT, 30 x 5XT, 14 x 108P, 42 x LA-RAK, 23 x LA8