In the northern part of Roskilde we are working with nice speakers for the living room, but in Roskilde South they are doing something completely different. Meet the speakers at Orange Scene.

Under construction. The Orange Stage is being built and the empty scaffolding will house some special speakers. Bottom left: Paul Jensen, responsible for stage technology at Roskilde Festival.

The trip lasts only 15 minutes by car, but might as well have been a journey to another planet. That's how different the challenges are when you compare living room speakers to the ones currently being set up on the Orange Stage. I met Paul Jensen, who has been responsible for stage technology at Roskilde Festival for more than 25 years.

L'Acoustics K1. The French loudspeaker system, of which there is only one in Denmark.

French speakers on the Orange Stage

On either side of the Orange Stage you'll see a scaffolding with the easily recognizable Tuborg logo. This is the home of some very unique loudspeakers, so unique in fact that there is only one such system in Denmark. The speakers come from French L'Acoustics and are their so-called K1 system. You can read more about them here.

Paul Jensen has worked with the speakers from L'Acoustics once before, as they had their premiere on the Orange Stage last year. The desire was to give festival goers a better sound experience and here the loudspeakers' use of line array should be particularly suitable.

Speakers are hoisted up. Clusters of loudspeakers form line arrays (line sources).

Line array covers the space with sound

Paul Jensen calls the French loudspeakers "bananas" because they consist of clusters of loudspeakers hanging in a curved formation. Each cluster consists of 18 speakers that make up a so-called line array. The way it works is that when the speakers are stacked in this way, they will (acoustically speaking) connect to each other and radiate sound in a particular way.

The advantage is that the volume does not decrease as quickly from a line array as it does from a regular speaker. The sound stays (almost) the same, even if you move closer to the speakers.

This is undeniably an advantage when 50-60,000 people are gathered. It's not very good if the audience has to crowd together to hear what's being played. It can end up being dangerous. So the smart thing about Orange Stage's line array is that you don't have to get close to the stage to hear the music, and many guests intuitively stop a distance from the stage because they find that the sound doesn't get louder as they get closer.

It's technology and knowledge of human behavior in beautiful harmony.

Lens from lighthouses behind sound patent

In the 18th century, the Frenchman Fresnel invented a lens used, for example, to concentrate the light from lighthouses. In 1992, physicist Christian Heil applied Fresnel's theory to sound waves, laying the foundations for the Wavefront Sculpture Technology at the heart of the K1 system from L'Acoustics.

Christian Heil, who incidentally founded L'Acoustics in 1984, is called "the father of the modern line array".

An achievement that has changed concert speakers around the world.

Overview. Here you see the Orange Stage with the main speakers marked with PA and the delay towers placed behind the mix of sound and light.

Cardioid array sends the bass forward

One of the challenges has been that the Orange Stage has drowned out the surrounding stages with heavy bass sound. The sound of bass is emitted like ripples in the water, and this has meant that there has been just as much bass behind the Orange Stage as in front of it. According to Paul Jensen, this has been managed much better with the help of the 24 18″ subwoofers and ultra-subwoofers, which are stacked in a special arrangement in each of the speaker towers.

They form a cardioid array that should make it possible to direct the bass sound so that only the audience in front of the Orange Stage can enjoy the sound. Clever.

Point source vs. line source. At the top you see a simulation of the sound intensity from a near-point source. Bottom: the sound intensity from a line source. It is clear that the volume is maintained (red color) even when you move away from a line source. Source: Meyer Sound

Less wind sensitive speakers

When you, like Paul Jensen, are responsible for covering a 165 x 120 meter space with sound, where there are 50-60,000 spectators under the open sky, you face challenges that are not found in your living room.

For example, it is important that the Orange Stage faces from north to south, because in Denmark we often have westerly winds. This causes some of the sound to blow away and the technicians have to be aware of this at all times.

Paul Jensen says that evening concerts in the open air are a particular challenge when the temperature drops. The heat from the audience rises up towards the night sky and can cause the "sound to bounce" off the crowd, which is said to be a peculiar phenomenon.

A job well done. This is what it looked like in 2011 when the L'Acoustics loudspeakers were ready to receive the public.

Technicians are trained for the K1 system

When this year's headliner takes to the stage on Saturday night, he/she will have brought along a number of sound engineers trained in the use of the K1 loudspeakers. They know the speakers as the working tool they are and have worked with them many times.

At Roskilde Festival, it is not possible to make sound samples before the orchestra goes on, so it is incredibly important that the artists and technicians can trust that the sound is right, right from the first stanzas. Therefore, the loudspeakers are set up in a very exact way that is always the same, no matter where you encounter them in the world.

It's all about quality, says Paul Jensen, and suddenly his planet doesn't seem so alien. Still, I would have liked to ask him how long it takes to turn on 167 1800 Watt amplifiers.