For the past 13 years, Arnhem’s GelreDome Stadium has been the home of Qlimax, an all-night hard dance music event staged by Dutch entertainment enterprise Q-dance. In recent years, the high noise levels have generated numerous complaints – despite the stadium’s retractable roof being closed – to the point where a public debate was held as to whether the shows could continue.
Official measurements were taken, with the noise levels revealed to be well above the legal limits, particularly in the bass frequencies. As a result, the Municipality of Arnhem stopped issuing overnight permits for such events.
Q-dance, audio rental company Rent-All and specialists Focus Advanced Facilities worked together to find a solution which could significantly reduce the noise nuisance or, even better, remove it altogether.
“The audio system comprised four large arrays at the stage and four delay arrays in line abreast, halfway down the stadium. They had to cover large distances and, therefore, put out a lot of energy,” says Ben Brouwers, sound consultant at Rent-All. “The roof was a big problem because it’s made of 3mm steel plates and resonates at around 50Hz. The exterior noise measurements showed that most of the spill, especially the low frequencies, came from there and behind the stage.
“After considerable research and testing, the results showed that it would be possible to continue with overnight dance events if we redesigned the system. We presented a plan to the Municipality of Arnhem and were given two chances, which would be closely monitored.”
The test results suggested a solution whereby, instead of flying one large line array at the stage, the sound system was broken down into a set of smaller, distributed line arrays.
“The most important part was removing all the low energy from the roof, so we needed to achieve as little low-end frequency behind the speakers as possible,” says Brouwers. “When we hung the line arrays with a cardioid sub array behind it and applied delay and filtering, we achieved between -12 and -18dB to the rear, but with really good coupling at the front.
“The combination of these arrays were flown with a very sharp downward angle, meaning that the back of each array was pointing towards the roof rather than the back of the stadium. This had the twin benefits of reducing the sound projected to the rear of the stadium and also that the roof was subject to much less energy, between -12 and -18dB in the 40-60Hz range.”
He continues: “Positioning more arrays closer to the audience also meant that each one could push out less energy, because the entire audience was always in the nearfield of one of the arrays. So, while we were still achieving around 103/104dBA and around 122dBC (LAeq three minutes) on the dancefloor, the overall energy levels outside the intended coverage area were much lower.”
The two ‘test’ events with the redesigned system permitted by the Municipality of Arnhem passed all the sound pressure tests and so Qlimax and other all-night dance music events at GelreDome Stadium were given permission to continue. This last Qlimax, held in late 2015, proved the success of the concept.
“Eight years ago we had 200 complaints from local residents, this year complaints were down to virtually zero,” says Brouwers. “It has also had significant benefits for the Qlimax audience, because the sound quality has substantially improved.”
This year, the system was redesigned using four lines of delay system (a combination of six L-Acoustics K2 and with three K1-SB at the rear. An additional, and major, advantage of this is that the total weight of the PA system was brought down by 6000Kg and the installation of the system was much simpler.
Indeed, so successful has the design been that Focus has implemented it at other events and been working to improve it further.
“Other major customers and venues have also heard about the solution and are interested in its potential,” says Brouwers. “Every year we are improving the system, and we have recently started new tests to make the low end more directional, so that you can hang some subs that will beam down, not above or behind.”
Photo Credit: Q-dance