A few months ago, we got a call from a pastor about the sound quality in the main worship space. He talked about uneven coverage, uneven sound pressure levels (volume), lots of low-midrange rumble at the podium and a general lack of audio fidelity. He seemed like he was ready for a new sound system.
We asked what he had installed now. Bose 502A. No problem there. Was he using the system controller? Yes. How and where were they installed? In a center cluster, about 5-6' directly above the podium microphone (see below). Uh oh.
This is not how to do it.
Two things stuck out to us. First, the center cluster was low. Of course, the ceiling is low, too, so options were limited.
Low frequency pattern control is a big issue that most don't consider when it comes to a new system. The short story is that...
...a loudspeaker radiates the lower (bass) frequencies around the speaker (forward, back, down, up) as opposed to being more able to direct those frequencies more toward the audience. That's the way physics works. There are certain speakers that have better ability to control low frequencies by directing them, but that's a discussion for another article. The proximity of the Bose speakers (or just about any speaker) to the podium was the primary cause of feedback in this case.
The worship space in question is 52' wide, 62' deep with a 14' ceiling and a 28" raised platform. That ceiling height makes it very difficult to maintain nice, even coverage from front to back. Again, that's just the way physics works. If you're interested in a geeky sort of way, Google the phrase "Inverse Square Law" and you'll have plenty to read.
In the end, we had the client move the speakers to approximately +/-16' from center and change the down angle a bit. That removed the low frequency lobes from above the podium (and put them over an area of the platform where it didn't matter) and separated the speakers so that they no longer interfere with each other as much as they once did. The Bose 502A has a nice, wide horizontal coverage pattern, but that's exactly the type of speaker that needs more physical separation and/or more splay angle between them. More splay would not have worked in this situation due to dimensions.
Here are his comments. "Moving the Bose 502a speakers as per your advice has made an incredible difference in the sound of the room! We couldn't be happier even though there are still a number of steps yet to do (tweaking and tuning things). THANK YOU! You are the one who put us on this track! What a difference in coverage and fidelity!"
Many times, we see bad installations of good equipment, and simply making the right changes is a great "no budget" improvement to make.