2. “Fake Delays”
With due respect to Normal Rockwell, this is the problem that audio engineers all live with: the inverse squared law. The level becomes quieter as we move back in the venue. Outdoors, there’s a very significant level difference between the front and back rows. Indoors, there’s less of a level difference (because the walls contribute reflections), but there are very serious intelligibility problems (because the walls contribute reflections). The obvious solution: add more loudspeakers further back. Great. Love it.
Here’s the problem: The sound from the main system takes some time to get to the back of the room. How much time? Just under 1 millisecond per foot. It doesn’t sound like much, but since the loudspeaker we added is much closer, its sound waves have a head start, so listeners in the back of the room are getting two separate arrivals of the same signal, spaced apart in time.
So we’ve actually made the situation worse by adding our own (artificial) reflections to the mix. Even if the difference in arrival times is not large enough to be perceived as a separate arrival (an echo), the signals combine in a way that can severely impact intelligibility. It’s called a comb filter, and we’re not getting into the math here, but if you’re interested, I highly recommend “A Hollow Quality: Exploring Comb Filtering & Flanging” by Bruce Bartlett, available here on ProSoundWeb.
Math aside, it’s a general rule of sound reinforcement that multiple arrivals spaced in time are problematic. Since the loudspeaker that we installed further back in the room had a head start, we need to electronically delay its signal to give the sound from the mains a chance to catch up.
I see a lot of churches with “delay” loudspeakers that aren’t delayed, and they don’t realize that it’s actually making things worse. Trust me, it very much matters. Most modern digital consoles offer output delay, and so do newer amplifiers with built-in signal processing.
There are also a bunch of standalone options that can be inserted into the signal chain between the mixer and the power amplifier to add the appropriate delay. Fixing this problem is not costly (for example, a Behringer Shark FBQ100 offers a single channel of delay for about $100) and, from a system optimization standpoint, might be the most important change in terms of improving things in the back of the room. For additional information, see Why Wait? The Where, How & Why Of Delay Loudspeakers by Mike Sokol.
3. Crazy EQ
I’ve covered this issue at length previously (“EQ Boot Camp“) and encourage you to revisit it The short version is that each EQ in a sound system has a job: input EQs fix problems with inputs, output EQs fix problems with outputs, and system EQ handles the system in the room.
Once we start trying to fix room issues with input EQs, we start chasing our own tails in a way that’s very hard to recover from. In a properly equalized signal chain, hitting the Solo/Cue/PFL (pre-fade listen) button at any point (input, mix bus, output, matrix) produces a correct-sounding signal.
For example, if the subwoofers are delivering too much low-frequency energy for the room, and you try to roll off that energy using input EQs, the mix will sound thin at all points in between. In contrast, using the system EQ to address the issue will result in a mix that sounds as it should at every point. Basically, don’t call in an EQ from out of town when the neighborhood EQ will do.
I’ve focused on problems common to church sound systems. Problems with church sound system operators is a separate article, but a very important one, so here’s the one-word sneak preview: pride.
I can’t tell you the number of times that the issue was not gear-related at all, but rather a member of the church who insisted on being the authority and having all of the answers, even when that person didn’t have all the answers. This is wrong statistically (What are the sheer odds that you know more about this topic than everyone else in the world?), and it’s wrong empirically (If you have all the answers, then why is the system still experiencing issues?), and it’s also wrong temporally (Even if you knew everything last month, there’s more to know this month.)
Solutions are often as simple as connecting the patch cables differently or aiming the loudspeakers differently, but so many times these simple fixes are prevented by folks who are territorial over their systems and don’t want anyone “messing with their sandcastle.” Getting this right requires a spirit of humility and the ability to be at peace with not having all the answers.
If you don’t know, say you don’t know. If you need help, ask for help. If you’re not sure how to do something, go read about it so you can learn. It’s the right way to transition from knowing some things to knowing more things, while those who “know everything” are forever stuck in the metaphorical mud. Here’s the good news: You’re reading this article right now, so you’re headed in the right direction.