I was recently asked to take a look at the sound system at a small church across town.

Upon arrival it was immediately obvious that acoustic treatment is needed in order to make the space work with a sound system. Excessive low / low mid energy is an understatement. In discussing the matter with church staff, it was revealed that the space is rented and the church may move to a different space if there can’t be some agreement about long term leasing. What this means to the project is that whatever acoustic treatment is added needs to be portable and inexpensive. With that on the table, we have done some experiments in the space to figure out which speakers might be a good fit for the space. We tried a pair of QSC KW122 as a 75 degree sample and a pair of borrowed QSC K10s for a 90 degree sample. Arguably the KW122 pair sounds better than the K10 pair but the K10 pair covers better. It was decided that a pair of K10 will be purchased.

The current configuration is a pair of Mackie Thump TH-12A at the outside corners of the room.

A few issues with this setup. In order to cover the space, the current mains are cross firing which is washing the side and back walls. The speakers are actually audible from the podium so there is a chance for feedback. The speakers are so far apart that the imaging of the PA is outside the entire direct source zone (the stage). Sadly this is a typical situation. Where speaker placement is dictated by the layout of the space. The solution is to fly speakers overhead.

Today I returned to swap out their AudioTechnica podium for an Earthworks Flex mic (huge improvement) and also to do some corrective parametric EQ on the current system. The church owns a stereo 15 band graphic EQ which up until today was inline with the main L/R speakers. I loaned them a Yamaha YDP2001 parametric digital EQ / delay to cover the mains which freed up the graphic eq for the monitor send. The orange trace below is the flat trace measuring only the HR speaker. The Pink trace is a post eq measurement from the same mic position and with the same single speaker. Note that we took a few measurements with the new EQ and the results were fairly consistent.

The orange trace below is the same measurement as above (flat). The green trace is with the mic in the middle of the two speakers with them both producing sound.
One would expect a rise in low end when you measure both mains at the same time instead of only one.

After some corrective eq, the PA doesn’t sound terribly bad. It certainly sounds better than it did without corrective EQ. When you listen to music, it’s a bit on the thin side but that is a condition dictated by the acoustics of the space. Any low / low mid source sings in the space without any amplification. Consequently, the PA needs to avoid those frequencies. Once the church purchases the new speakers, we will install them overhead and locate them in toward the center of the space so the imaging is more accurate. Hopefully there will be support for adding some acoustic treatment which is going to take the venue to a new level.

Some lessons to take away from this project.

1. If the acoustics of a venue are bad, no amount of sound system is going to fix it
2. If the acoustics of a venue are bad, resolve them before you make final decisions about any sound system upgrades

In this case, the existing speaker positions are not ideal and the exiting speakers can’t be hung (no rigging points) so it’s a safe decision to get new speakers that can be rigged overhead and located inward. The existing pair of self powered speakers can become floor wedges. Stay tuned.