Updating the Worship Center: Acoustics

We just finished installing new acoustic treatment for our room, so I wanted to walk through the process we went through in redesigning the treatment.

This is a pretty challenging room to mix in. It is wide, and asymmetrical: The balcony only goes around the back and one side, with a third leg never built. The PA design is a bit, um, unique: it was originally installed as an LCR system, with a delay ring for the balcony, plus a mid-field delay ring for the back of the floor. However, the design used the same boxes for the front clusters, the mid-fields, and the delay ring. That translated to a lot of energy from a number of point sources. Additionally, the balcony ring was installed quite a bit further into the room, resulting in a pretty flat address to the seats – a lot of energy hits the walls, as well as the seats. To compensate, a bunch of panels were built from rock wool and installed, covering most of the balcony walls, and about 60% of the floor walls. The result was that the balcony felt like a separate room, and lent itself to a more observational, rather than participatory, experience.

The program matter has also changed significantly since the design and installation of the PA. Instead of mostly choir, orchestra, and track accompaniment, we now do an indie-rock flavored band, and instead of mixing at 84-87 dB-A, we’re mixing at 96-98 dB-C, or around 95 dB-A.

So, common complaints included:

  • Mix harshness, with uncontrolled low-end;
  • Feeling isolated in the balcony;
  • Not being able to hear the rest of the congregation.

My predecessor brought in an acoustical firm to assess the room, and their primary recommendation was to reduce the damping in the room, and to add some diffusion to increase the sense of space and people. I took it a step further to change the absorptive material on the floor from rockwool to compressed fiberglass, for a more even absorption coefficient across the spectrum. Rockwool absorbs quite well in the midrange, but is less effective in low frequency and high frequency bands.

This refresh was a good opportunity to replace everything, since we had to replace it to coordinate with the new wall colors.

The first step was removing all of the absorption panels in the balcony, to confirm that we did need to liven up the room. We lived for about 4 months with no treatment in the balcony, which definitely gave a gymnasium slap-back to the room. But it was an immediate difference in the balcony experience. Because it wasn’t totally dead, it didn’t feel like balcony-dwellers were listening to the PA, but to the room.

We worked with CCI to design the diffusion for the balcony, and went with an extruded PVC product from Kinetics Noise Control, with a mixture of fabric and paint coverings. The result blends into the wall, but gives texture and a sense of intentionality to the space. It has significantly reduced the echo of the room, compared to bare walls, but retained a sense of spaciousness.

The main floor panels were replaced with some Kinetics Noise Control absorptive panels, and have tightened up the bass response of the room, while providing enough deadening to smooth things out. In addition, I’ve converted the front line of the PA to mono in the processor, and am experimenting with turning a few of the boxes off in an effort to reduce the number of point sources in the room.