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Oslo, Norway | July, 2012 – The Sofiemyr church in Oslo is a striking modern building, with bare brick walls, a tiled floor and wooden ceiling. Light pours in from a huge stained glass window and other windows in the corners.
The audio solution, supplied by Benum A/S, is equally striking, with a pair of inverted IC Live arrays, flown from the ceiling alongside the matching subwoofers, above a small performance stage. The technique has been used before – England’s Stage Audio Services was possibly first to experiment with it, flying a pair of IC Live arrays upside down at trim height for a standup comedy tour of UK theatres, which allowed the beams to be angled at the ground floor audience as well as the balconies.
But this is almost certainly the world’s first permanent installation to use the configuration, which has many benefits in a tall space.
Geir Kristoffersen, manager of the consulting department of COWI for Acoustics and Electro Acoustics, Sound and Vision, who designed the system for the church and frequently mixes it, explains: “This room is a cube, essentially, 16 by 16 metres with a height of about 12 metres, so it’s very interesting acoustically. But it’s turned 90 degrees so that you get some angles towards the speakers.” Slots in the ceiling provide low frequency absorption.
Although on the face of it a highly reverberant space, the actual reverb time is just 1.7 seconds with a very well controlled low end. “But still, 1.7 seconds is significant,” he points out. However, the bare brick walls are an inevitable challenge in view of their capability to deliver slapback echo to the stage.
The church is also equipped with a pipe organ, which is quite frequently played together with a band and a grand piano, as well as a movable pulpit, which is taken out during modern-style worship services.
“The loudspeaker system is flown in the form of a pair of Renkus-Heinz IC Lives,” says Kristoffersen. “We’re very happy with the sound of it. In fact, I’ve never worked with a system that’s so easy and quick to get good sound out of.
“It works exceptionally well for this kind and size of room and with such a wide variety of music. Together with the choir, we often have a worship team of eight people singing with their vocal microphones.
Last Sunday, for example, the choir was seated directly in front of the loudspeakers and I had my measurement system at the desk and I was pumping 90db A weighted but flat out it was giving 101dB. Yet there was no issue with feedback.”
“What I particularly like about these loudspeakers is the line array design,” says the consultant. “We could get this type of sound pressure level from other types of loudspeakers, and that would give us adequate sound.
But with these digitally steerable arrays we get tightly controlled beams, which allow us to deflect the sound away from these noisy brick walls. While there is some reverberation, of course, if you shoot straight into these walls then you’d have a big problem with slapback.”
The system is configured with two beams from each IC Live, one pair aimed at the front part of the congregation, the others at the rear. The result, says Kristoffersen, “is that the sound is completely uniform wherever you are standing or sitting, and there’s no reflection from the walls.”
He continues: “We also get a very good dynamic range from the system and it projects the audio clearly even at very, very low levels. Our priest is very dramatic in her presentation and you have to follow her and ride the fader!”
“What I like the most about this system – and I’ve worked with good systems all my life – is that because it’s a true line array and not a banana hang it creates a cylindrical wave, which means that it doesn’t excite the room as much as a traditional three-box system, which would have been our obvious alternative.”
“Another thing is that, with a choir, the choir bench is high, which means the microphones are right in front of the loudspeakers, yet we have never had any feedback problems. Because it’s so even sounding across the frequency spectrum you don’t get response spikes which then become the problem, especially with the choir-mic scenario.”
Tuning is performed using both RHAON and in an Allen & Heath IDR8 DSP processor with an Allen & Heath T112 control surface, allowing it to be controlled from two different places.
A small delay system provides extra coverage into a small annexe at the rear and in the side halls, using CFX-61R cabinets, again controlled over RHAON and CobraNet. These are matched with six CF-121M cabinets for monitors, which can also be deployed as a portable PA in the larger side room of the church, or outside during the summer.
Testing time
The testing and beam adjustment process brings the best out of the system, says Kristoffersen. “Before we adjusted the system I was doing a testing with a colleague behind the mixer. I was up on stage on a vocal microphone, doing the usual stuff I do when I test the system, and I could hear it bouncing back from the walls. This was for the youth service in the evening so we were pumping rock’n’roll levels. But then after Benum adjusted it and they got the beams set correctly there was nothing coming back from the walls, which is very good – I mean it’s very good for the singers because they actually get thrown off by this slap-back.”
He continues, “It’s also very good for the monitoring because despite it being so loud up there it doesn’t feedback even though it’s rock’n’roll loud in the afternoons. Also,” he adds, “interestingly, we work a lot with the grand piano and, for me, a grand piano has to sound good. If the grand piano doesn’t sound good then it’s nearly worse than having the drum kit not sounding right, which for all sound engineers is a terrible thing. Benum A/S suggested we try some huge Shure microphones – Beta 98s – and they work terrifically well.”
“In terms of levels, depending on where the piano is located, the limiting factor is the grand piano because it’s right in front of the right hand speaker. But even when we’re pushing rock’n’roll levels and there’s a monitor there next to it, if you do push it to feedback it’s not high-end feedback but a just rumble, which tells you that the total room is just playing too loud. It’s very impressive and we’re extremely happy.”