As we voiced the stadium "Spartak"

At the stadium "Otkritie Arena" 45 360 people fit - this is the audience of a good post on Habré. Photos at the time of the beginning of our work.

Approximately 9% of users during the match are busy shouting, making noisy noise and making fires. 90% of TK listen attentively to the commentator’s speech and advertising, and the remaining 1% spits and says that it would make the sound better.

It was these sounds (advertisements and speeches) that we had to convey to each viewer so that he, on the one hand, did not burst eardrums, and on the other he heard everything is normal and distinct. That is, it was necessary to ensure uniform coverage and high speech intelligibility for everyone.
')

Training

Stadium can be any. The open arena, like the former Dynamo or Luzhniki stadium (up to the Luzhkov roof), or partially covered, like most modern stadiums, where there is a roof just above the spectators. Or in general completely covered, like hockey arenas or such ambitious projects like “Fisht”, albeit with a temporary roof. There is no universal recipe for good sound in all these cases. On the one hand, fantasy acoustic engineers are usually limited by the budget, and on the other hand, the requirements of the TOR are to combine the system with SOUE according to all Russian standards and the possibility of equipment placement. We are going to voice the stadium Spartak.

Model

Omit financial interactions with the customer. Immediately, we note that any sane person, before making a proposal for the voice of the stadium, will prepare a computer model. Without it, it is difficult to get into the TZ, even approximately, if there is no experience behind. Of course, there is a nuance of modeling - this is the accuracy of the model, and the characteristics of the materials used, and models of acoustic systems, and noise accounting, a mathematical modeling method, and much more. And many more reasons to challenge the correctness of the calculations. But this is the only thing that will give results in a situation where your object looks like this, at best:



Of course, you can wait for the construction readiness, take measurements and insert the real RT60 measurement results and impulse responses at the test points into the model. And it will be right. It will be as correct as possible. But building something is a fun thing, surrender the day after you are given tension and paint over the last flight of stairs. All systems are dealt at the same time, do not look into contracts, do not write letters - this is a reality.

Based on the architectural drawings of the object, we were able to reproduce its shape, but the second problem remained - materials. And if the plastic seats, concrete structures, lawn could be taken from reference materials, then the rest was difficult (for example, it was impossible to tell what the absorption and scattering coefficient of gravel covering the roof of the western sector was). By the way, an unbelievable amount of communications is found under the field itself, but only the top layer with grass and earth is important for us - the rest did not affect the sound propagation.

The following was important:

• Maximum uniformity over direct sound coverage.
• The energy of the direct sound of acoustic systems should always be greater than the reverberation tail (at least in the first 50–80 ms, very simplistic). Those. We look at the value of the coefficient C50 and C80.
• The stronger the systems are, the more likely they are to get into the TK.

In general, when we talk about sound, you need to understand that sound is not light. These are 10 octaves, these are waves that behave in different ways - some quickly fade out in the atmosphere, others bend around everything and everyone. At a distance of 30-40 meters is not the limit for stadiums - you can see a lot of everyone.
So, when the model was ready (it is convenient to draw in SketchUp and then export to EASE 4.4 or Bose Modeler 6.8), we set the boundary conditions and drove it into the calculated software. Preliminary data were disappointing: the reverberation time ranged from 5.5 seconds at a frequency of 512 Hz. This is a lot. Imagine: you turn off the music, and the last chord sounds for another 5 seconds. But in the TZ it was prescribed - to organize a sound system without changing the architecture or introducing additional materials.

Cable

Ok, another week of work together with the equipment manufacturer and a more or less realistic layout of the systems and their models emerged. The spaces of the stadium are long tracks. Long cable runs of fire resistant cable. Loading a long line with big power is stupid. We will lose more in the cable. A high-impedance load is needed, either 100 V (but in the transformer sound there are complaints about the quality and power limit of 400 W), or 16 or 8 ohms. It would be nice to break the system into well-directed satellites and a low-frequency section, which can also be sent by EndFire or a cardioid, so that the bass does not hit the roof. Of these conditions, there is not such a large selection of decent brands - the installation version of the expensive JBL PD series or horn ElectroVoice, LT from Bose or ARCS from L-Acoustics. There are others. But look at sensitivity, pressure, dispersion, input resistance, weight, and, of course, price.


Fragment of the sound pressure calculation scheme, different scheme of the voice acting of the upper and lower tiers

It became clear that for work we will use Bose LT speakers and Bose PowerMatch 8500N amplifiers. It turned out that the cost of this equipment is half the estimate, the rest is installation work, suspensions, cable, trays, software and other peripherals. So, the basis of the project is a distributed horn system created by the manufacturer especially for stadiums and similar objects - two rows for the upper and lower tiers of the stands, 72 subwoofers, assembled in assemblies of 3 for EndFire.



It is high-resistance (8–16 Ohm), it can be successfully loaded on a long line. Bose LT is only 560 watts at the peak, the pressure is 134 dB (on average, depends on the model), that is, the cable cross-section is not the greatest (which saves the budget, because the requirements for a cable on this object are almost as in space). The longest line from the amplifier turned out to be 90 meters - naturally, the whole section was calculated according to the attenuation level, taking into account weather inductance, dumping factors and others.

Once again checked the entire scheme and proceeded to the installation.

Installation

At the end of February cable systems began to arrive. The requirements for the installation of the cable and the cable itself were among the most stringent: the warning and evacuation control system was, after all. Top-level security (for example, we used the most non-flammable cable of all cables of this diameter on the Russian market - the German KLOTZ and Sommer). By the way, the whole office laughed at us - we actually took samples of the cable and burned it. Specifically, with this (Klotz LSE440) it turned out like this: we burn, but it does not burn. We burn further, but it does not burn, foams, turns black, but does not burn, the veins remained cold after 10 minutes under the direct flame of the burner. It means that it fits (as the simple working people broke off, who collected pieces and pieces of cable in order to burn and give the color to the reception).



First of all, we mounted suspensions for all systems. Systems gathered in clusters, it was necessary to clearly position the module relative to another to accurately cover the stands. People of the general contractor walked around the stadium and took pictures of every joint with German pedantry. Burr on trays - photo, on the carpet, redo.

The installation took place at a height of 30–35 meters above the still unfinished (and also, of course, unseeded) field.

Then the speakers began to arrive - 184 pieces (these are two and a half trucks of heavy equipment). All this was put on the warehouse, which was 300 meters from the stadium. In the morning, a car with a tail lift drove the speakers to the site, if the installation team did not have time to place them - then dragged them back. We did not know how to install such large objects at the start of the project, also did not understand how much time was required for the site and what the optimal procedures were. At about the 10th column, it became clear how to optimize the process, but at the 40th level, everything was already done on the machine and was documented. The cluster weighing up to 350 kilograms needed to be raised by electric winch, but we were not given electricity. More precisely, they gave, but only later, as a gift for the Day of sovereignty of Russia. Therefore, we bought a three-phase diesel generator for lifting in order not to depend on anyone. In April, finished weight.

The third part was the installation of the cable - from the racks of the amplifier equipment to the speakers. The racks were collected in the office and tested (6 reinforcement racks, 48 ​​amplifiers). These racks, by the way, are in all-weather performance - there are temperature, humidity, fire sensors, information about the opening of the rack. We assembled the first stand in the office and plugged it into a regular outlet without thinking. They didn’t even include the main functionality, but still the group of sockets flew out entirely, hello to the housekeeping).

It was not limited to tests, it was necessary software. The IP controller controls all hardware, polls all devices, and they need to be programmed. They remove statuses from all the equipment, for example, the amplifier can detect line breaks or short circuits, but the amplifier needs to be asked about this, and all the resulting LOG file from the amplifier should be converted into a clear view of the user - the red and green lights on the monitor, etc. As a result, the controller at the stadium now works with 95% load, collects all the system statuses into a large file and sends it out through our API. We see open lines, dangling, short-circuited, improperly loaded, and so on. Why was this necessary? Because - ta-dam! - in the TZ it was prescribed that our sound system also connects to the alert system in emergency situations and alerts to the stadium bowl. And for warning systems, all these standards are strictly regulated.

Testing the monitoring system

Usually SOUE, such as Bosh and Inter-M, use tone generators at 100,500 KHz, which analyze the integrity of the line, stand at the ends of the lines. We do not hear them, but the data is analyzed by the return signal, counted over long distances. But these systems are not ice, and they are not designed for such large capacities that are not assumed in the CO systems (the manufacturer had to do a separate job of equipment certification).

What happened

In April, about seven and a half kilometers of cable with a cross section up to 4x6 (multi-core, to eliminate the skin effect on HF, oxygen-free copper) were installed. All connectors, of course, soldered, because the power is large, all on the air. For a 6-square cable, a 300-watt soldering iron was used.

The project was agreed almost in 5 instances (up to loads on the roof, bridges, point and integral routes). Despite this misunderstanding between the subcontractors, it was all the same (for example, they wanted to deliver the light directly to our assembly point, but then the lighting was mounted a few meters further).

Customization

Before starting the system, it was necessary to remove the polyethylene from the cabinets, which protected it from construction dust. This is a separate joke - we hired a local mountaineer - our team broke the anchor and was at another site. Watching him hang on clusters is a controversial sight. But when it got dark, at about 12 o'clock, his appearance didn’t bother us much.

We conducted the first test on the switch in 4 Ohm sabe - just clarify how it works, and it was very convincing. In order to hear something on the sub, we had to twist their amplifiers almost to the full, up to 18 dB. The fall on the 60 m line was just huge (hi to amplifiers with a dumping factor of 100.5 million). Now there are 8 ohms per line, the losses have decreased significantly - amplifiers by +6 dB, bass is well heard. Colleagues, do not save on the cable!

Work had to be done both during the day and at night, which the locals were not very happy about. In the residential complex in the neighborhood it was constantly audible, as we hiss, boils, whistles and periodically play tracks Simply Red and the Nine. They checked the polarity of each cabinet, lowered the microphone on a fishing rod to the speaker, then drove the test signal, looked at the results.

By this time, installers and engineers are no longer afraid of heights.

We didn’t work out verification methodologies either, and this became a problem at some stage. The fact is that since the system is integrated with the evacuation control system, it was necessary to ensure operation even when several amplifiers failed (to make a safety factor). We made sure that each cluster was connected to different amplifiers, and when one unit fell, the sound in the sector remained, however, became less discriminating. Because of this, at first it took a very long time to look for schemes where what. Then we made special check cards, and things went much easier.

And still it was necessary to understand whether they got into the model by measurements. They started everything, checked it out on an empty stadium (it was calculated with a 70 percent load from the audience). The RT60 in an empty stadium really turned out to be a little more than 5 seconds over a larger frequency range. They drove new data into the model, devastated the model from the audience, updated the materials. It turned out that they got very accurate, only minimal adjustments were needed. Thanks to the creators of Bose Modeler and EASE, it turned out very precisely, although the mat model of the programs are slightly different.

Then they began to measure speech intelligibility. With preliminary measurements at an empty stadium, we obtained quite good legibility values, with direct measurement of the MTF. Delighted. A special “man-ear” came to take the job. We walked with him for about three hours, showed TZ, pressure data, average characteristic, numbers (105 dB per place, 106–107 at the peak, 110 right in front of the speakers). Peak values, by the way, were measured using rock and roll. He provided 115 at peak on a number of places under the columns. Restricted gain percentage (despite the fact that there is a limiter, so as not to set fire to the speakers). We felt the need for limitation on ourselves - to experience what we experienced, standing at the bottom with a microphone - something else is an adventure.

There were test launches in beta. For example, stadium workers came to watch the match Russia - Belgium - 2014 on the big scoreboards. We took the sound from the broadcast and drove it into our system. Commentators and advertisements sounded good, but rap - extremely unintelligible, literally - porridge. Scorpions were heard, on the contrary, perfect.

Having conducted several test events, they began to move inexorably toward the official opening of the stadium. And here we ran into a problem that we had not thought of before. It turned out that even the most autonomous complex must be managed. You need to follow him. It is necessary during the events to work at the console, prepare the content. At the next test, the beta team of the stadium operation tried to build up without our help (and without the sound engineer). The sound has deteriorated sharply. They called us to find out why this happened. It turns out that the main and backup signals were mixed together. Understanding that at the initial stages the team of the stadium itself cannot cope, we accompanied the first events ourselves:



A rental company was invited to the opening, which used not only its own sound, but also our stationary sound. Without our knowledge, without the knowledge of Spartacus. It was ooooooochen loud. Before the discomfort in the ears. Operating a sound system without relevant skills is not easy. After several matches, unofficial complaints went - the sound was unintelligible, quiet, loud, too loud, echo, etc. It should be noted that the intelligibility of speech very much depends on the level of SPL. The louder the sound, the more illegible the sound. You need to follow this. Optimum 85-90 dB. Well, the sign object - began to understand. Now with Bose. They scored twice as many instruments, microphones, smart programs, 300 m wires, and sat down on the object for a week.

We started with measurements by impulse response. Sweepers were chasing (by the sound it reminds “buuuuiiii”, Spartak joked that they were chasing birds at the stadium), they counted for different stadium loads. In general, if the stadium is empty and speech is clear, then the sound in the stadium will be even better.


Before adjustment

A week was taken of the characteristics of each cluster, they looked at how the work of the system changed, how the settings changed depending on temperature and humidity, found that several columns were simply physically disabled. What else happened during our absence is a matter of further tests. Unfortunately, to see if the column is fine or not is not easy. There are sounds from which even the limiter can not save, something like the delta function (Dirac) ...

Press room

We also did the press center. FIFA requirements regulate the equipment of the press center. For example, you need to provide 4 places for synchronic translation. But at the same time, these requirements are, to put it mildly, common. No one says in them that the translator needs to see who he is translating, and for this, cameras are needed. The first part of the work was the translation of standards into the TK language, the second - the customer's conviction that additional systems would be required.



The first time it was deleted from the estimate, and then it turned out that it was impossible to live without additional equipment - it was necessary to take data from the cameras and transmit it to the internal network of the stadium. There was a mass of pitfalls: auto-aiming on microphones, filters in racks, constant reconfiguration, and so on.

Sample

As a result, our integrated system included audio amplification subsystems (stadium and fan sector bowls), audio routing, audio broadcasting, interactive control, and equipment performance monitoring. Additionally, the press conference hall was equipped with a system of synchronic translation, sound amplification, video display, switching, and technological television. In racks under the roof 48 amplifiers with a total power of 160 kW are placed. Mounted 184 speakers, which together create a sound pressure of more than 105 dB. In addition, a local network is deployed to manage and monitor the operation of the complex.

The Spartak Stadium is one of the objects of the World Cup - 2018. Now this stadium is very seriously paid attention to: builders of stadiums from all over the world come to, look at the engineer, architecture, solutions, usability. They adopt experience - where is bad, where is good. Therefore, on October 26 we will again turn the knobs, exposing the best sound quality. Despite the fact that we do not have a service contract, and in the stadium maintenance team - the sound engineer, we want to show the maximum class at the matches.

Everything. If you suddenly stumble around a stadium that needs to be voiced, or a temple , or something else complicated, I can answer questions in the mail MVasilev@croc.ru or right here in the comments.