Chuck Harris spends most of his time in the recording studio producing, tracking and mixing. He's also toured internationally as FOH engineer with a wide variety of artists, and was, for many years, Chief Engineer at Integrity Music. He's worked with Don Moen, Lincoln Brewster, Paul Baloche, Israel Houghton, Michael W. Smith, and the Monterey Jazz Festival All Stars. Bishop T.D. Jakes, Tower of Power and many, many others.

And as impressive as his credentials are, we asked him to weigh in on the challenges of acoustic miking in church, a subject he knows equally well. He has lent his considerable skills in ministry as Media Director and   Media Pastor for two California congregations.

The title of this article is tongue-in-cheek, but it's true that acoustic miking is a real challenge, and as I reflect on it, I think that all too often, we set ourselves up to fail at it. Think about it: we're dropping our microphones into potentially hostile territory.

There are two major issues conspiring against our perfect sound scenario. We need to address those before we can expect our microphones to perform optimally.

You know it's that hollow ringing sound we get when we turn the volume up. There are several contributing factors to feedback, but it's particularly troublesome in smaller venues where sound reflections bounce off close walls. The cause? Resonant frequencies that interact between the speakers, the room, and the microphones. In permanent installations (like our church), I recommend doing everything possible acoustically to address feedback before addressing it electronically.

Here are seven steps you can take to acoustically minimize feedback issues at your church:

1. Make sure that your main speakers are in front of your microphones.
I'm surprised at how many churches install their speakers on the rear wall behind the platform, which places every microphone on stage right in the path of the audio that is coming out of them. This is a big no-no and should be avoided at all costs. Sure, aesthetics are important, but you cannot defy the laws of physics without consequences. Please, either ground-stack, place on tripods, or have your speakers professionally rigged from above, in front of your stage so that the microphones are all behind the speakers.

2. Minimize sound reflections with acoustic treatments.
In smaller rooms, sound waves are excited much faster and easier. Sound is moving energy. It travels through the air and bounces off surfaces just like any moving object. That's why its energy can build up faster and more profoundly in a small space.

Think of it like this: If I stand at one end of a large gymnasium and throw a super ball as hard as I can at the opposite wall, I'd have little chance of it bouncing off the far wall and having enough energy to reach the wall behind me without bouncing a few times first. But if I stand in a small bedroom and throw the super ball at the same velocity, I can probably get it to bounce several times off the opposite wall before it lose its energy and falls to the ground.

Just a super ball, as sound travels it loses energy over distance. In a large space, it will be much quieter and pose less trouble by the time the sound travels to a distant wall and comes back to the microphone. In a small space, we have build-up with a very complex set of frequencies.

Acoustic treatment can be accomplished through a combination of absorbers and diffusers. If you're having serious feedback problems, consider looking into this and hire a professional acoustician to create a plan for your space.

3. Understand that some acoustic instruments are very resonant and contribute to feedback. Acoustic guitar is the most common and one of the worst. This is where careful microphone placement comes into play. Avoid putting a mic right in front of the sound hole on an acoustic guitar. There is a lot of resonant energy at that particular place. Instead consider moving the microphone to one side or the other (closer to the neck, or closer to the bridge). For about ten bucks you may also purchase a “soundhole plug” that does just what the name implies.

4. Minimize stage volume as much as possible. (More on that later.)
Once you've dealt with the acoustic issues to the best of your ability, there are electronic techniques to further make your church platform a safe and easy environment in which to use your microphones.

5. Equalization.
A graphic equalizer is still one of the first tools a good engineer will reach for to “ring out” the frequencies of a room to minimize feedback. If you're not familiar with its use, you should do some research and plan to use it. Basically, it allows you to pull down the frequencies that tend to ring most in your room. This gives you more “gain before feedback” allowing you more level and clarity in your mixes.

6. Feedback suppression.
This is like an automated graphic EQ on steroids. Many purists will complain that it can degrade the sound quality, but if used carefully, it actually can be very effective and for small difficult spaces it can really be a lifesaver as it has narrower notches than a standard graphic and can pull down more specific frequencies more severely. Read up on these and see if you couldn't benefit.

7. Microphone choice and placement (more on that later).


The second weapon used to sabotage our pristine sound is leakage into the microphones. That is: every other sound that's bouncing around the room and on the stage that eventually finds its way into our acoustic instrument microphone.

I can't tell you how many times I've wrestled with the problem of a drum kit on the same stage as an acoustic piano. Let's face it: half the time, the drums are louder in the piano mics than the piano is. Houdini couldn't escape the reality that you just can't get your piano to sound good in that situation. And contrary to popular sound engineer lore, there are no singers with heads fat enough to block out the cymbals of a young drummer on an energy drink buzz.

Unlike feedback, which is resonant energy at certain frequencies and requires a bit of science to address, leakage is just plain old-fashioned common sense. Try to avoid putting your drummer next to the choir, or your acoustic guitar player next to a Marshall stack. Here are a few common sense steps to take to minimize microphone leakage.

1. Think through how you place the musicians and their instruments onstage.
Avoid putting something soft (like a harp) next to something loud (like a fleet of jackhammers).

2. Acoustic treatment.
This is where our treatment for feedback also benefits us. With proper absorption and diffusion, we can reduce the noise bouncing around on stage considerably. Baffling between instruments can also be very effective. Consider a drum shield around the drums, or shields around guitar amps. Even putting the amps off stage in a closet can be a great solution.

3. Lower the stage volume. This is huge. I know the guitar player wants to be able to express himself fully by being immersed in his own velvety distortion, and the bass player wants his (and everyone else's) heart to skip a beat every time he lays down the thunder, but seriously, am I the only one who kind of thinks this may be slightly narcissistic? Honestly, research the possibility of putting everyone on personal monitor systems. This gives the musicians the ability to hear themselves as loud as they like and lets everyone turn down their stage volume. This helps clarify the sound exponentially.

4. Use proper microphone technique, which is a brilliant segue into our next section.

 

Many years ago, I read the book by Stephen Covey, “The Seven Habits of Highly Effective People”. One of those habits is: Begin With the End in Mind.

That universally applies to running church sound. If you're about to put a microphone in front of an acoustic guitar, think about it for a few moments and ask yourself these questions:

• Is my acoustic space ready for this?
• What do I want this to sound like?
• How prominent in the mix does this need to be?

The answers to these questions may lead you down different paths.  For example, if your worship team is heavily acoustic guitar-driven, then the volume and sonic quality are very important. However if it's going to be mostly strummy rhythm tucked into the mix, then you can have more flexibility with the sound and you won't need to push the gain up so much.

Typically for live acoustic guitar miking I will use a small diaphragm microphone. The smaller, tighter diaphragm tends to respond faster to the fast transients of the acoustic guitar giving you a cleaner and crisper tone. To a small degree, this can balance out the woofiness of the instrument. Purely for tone's sake, a condenser microphone has the best tone for acoustic guitar so something like the KSM137 is a great mic for acoustic guitar.

The only time I consider taking a different approach is if the acoustic environment is difficult. If the PA is prone to feedback, or the musician is using floor wedges rather than personal monitoring (earbuds or headphones), then I may be tempted use a good old SM57 dynamic mic. The SM57 is much less susceptible to feedback and leakage because it doesn't have the sensitivity or the expanded frequency range of the condenser mics, but it does have a very good crisp and warm midrange presence that is very pleasing on the acoustic guitar.

The consensus is that acoustic guitars sound much better with microphones than they do with pickups plugged in direct. The microphone picks up the warmth and breadth of the instrument much more dramatically than a pickup can.

But sometimes in a live situation, feedback and leakage can be a profound issue, so here's a great solution for that — a compromise between the two:

Plug it in direct and place a microphone in front of it. By blending the two sounds, you can get the gain and presence using the pickup without as much concern for the acoustic issues.

You'll be able to blend in the warmth and fullness of the instrument with the mic and benefit from both methods.
Since you'll be using two channels on the mixer, you'll want to place them right next to each other for easy reach and visuals when working on your blend.

When checking the sound, bring up the direct signal first and dial it in with EQ and compression and then bring in the microphone and dial it up with just enough presence to fill in the warm, rich tone of the instrument.
The same principles apply to all acoustic instruments as they do to the guitar. But techniques will vary. For example, your church may have an orchestra. Well, just like a choir, strings are hard to mic if you have a loud rhythm section playing along. Typically you might use condenser mics at a bit of a distance (one or two mics per section depending on the size of the group and remember the 3:1 rule). Brass, however, can tend to be harsh so you may want to tone them down with good dynamic mics like the SM57 or the SM7B . Good condenser placement can give you a full, rich sound as long as you don't have too much leakage issues.

Sound is subjective and therefore requires for you to make some decisions on your own. I hope this article gets you thinking in a direction that will help you nail down these issues for your church:

1. Acoustics
2. Feedback solutions
3. Lower stage volumes
4. Proper microphone choices and placement

In addition to the microphone placement article in this issue of Shure Notes for Houses of Worship, Shure has excellent articles and free publications on its website that will give you in-depth information on this subject. I hope you'll take full advantage of those resources.

Shure Notes for Houses of Worship is grateful to Chuck Harris for sharing his insights and experiences.  Have a question for Chuck?  You can reach him at chucksmix@yahoo.com.