Solutions for Mixing in a Concrete Box

A room lacking sound absorption material can be a nightmare for mixing.  I’ve mixed in a few of these rooms myself.  From what I’ve found, a number of you mix in such rooms on a regular basis.  In fact, the most common question I get is, “what the best way to mix in a gymnasium?”

A gymnasium has;

• Concrete walls
• Hardwood floors
• And ceilings open to the steel rafters.

My first thought is always the same, “tear down the wall that’s facing your speakers.”  I have yet to have anyone take me up on that offer.  This leaves me with giving you more practical advice.

How to Mix in concrete Boxes

You must realize such rooms have two keys issues;

1. Lack of sound absorption materials
2. Lack of clarity and definition with loud volumes

Dealing with the lack of sound absorption materials

The lack of sound absorption means you are working in a highly reflective room.  Imagine throwing a rubber ball, as hard as possible, against the wall.  How many times would it bounce around until it finally stopped?  A lot!

There are two steps you can take for slowing down that rubber ball (reducing the amount of reflection in the room).

1. Optimize speaker direction.  When you set up the speakers, how much of the speaker’s sound field is pointed at the chairs and how much is pointed at the walls. You might be bouncing much of your sound off the walls before it ever gets to the people in the chairs.  Therefore, turn those speakers inward for a tighter focus of your sound.

Consider these two setups and notice where the sound is traveling.

2. Add any type of sound absorption.  Now with the speakers angled inward, it should be obvious most of the reflected sound will come off the back wall or the far end of the walls.  You have a couple of options as to what you can do.  First, build modular panels that can be stood up across the back of the last row of seats.  Cover these panels in a heavy dense cloth.  You could build these out of PVC pipes.  They won’t stop all sound from reflecting but they can cut down a lot on the reflection.  Second, use the el-cheapo method of putting stuff behind that last row of chairs, such as plastic plants and coat racks (with coats/clothes).  All solutions aren’t necessarily pretty.

Dealing with lack of clarity with loud volumes

You can’t get a great loud volume in these rooms.  I know a place that has a highly reflective room and they have really loud concerts…and I’ve never felt like any of them sounded good.  What they needed was less volume to deal with the room dynamics.

Volume and reflection in mind, you are dealing with volume in two places; monitors and main speakers.

This is one area where I see sound techs differ on their approach.  Some techs will say, in such environments, they set the monitor levels first and then the house levels.  The standard operating procedure, of course, is mains first and then monitors.  Try it both ways.  It’s also a great time to recommend in-ear monitors to the worship team.

Once you have the overall volumes the way you want, lower and raise the master fader and listen to the resulting sound.  Eventually, you’ll find a volume that works for your room by getting the best mix clarity and definition possible.

The Take Away

There is no magical solution to getting a great mix in an acoustically nasty room where you don’t have the option of adding permanent and professional acoustic treatment.  You can, however, modify your setup for creating a better environment.

Make your speaker setup as directional as possible, watch your volume, and consider methods for absorbing sound behind the last row of chairs.