Constructing a new sound booth in an existing sanctuary is not an easy task. Designing a booth for your church requires consideration of three topics: line-of-site, location and security. 

Line-of-Sight
This is probably the most important piece of information you should know--sound booth operators should hear what the congregation hears. A booth located out of direct line-of-sight of the main speakers will only receive sounds reflected off the walls and the floor.  This reflection causes sound to be perceived as softer and muddy. This results in the sound operator increasing the volume in the main speakers so they can hear, thereby blasting a higher-than-necessary level of volume into the majority of the congregation.

Additionally, sound booth operators should see all areas of the pulpit (stage) area. This allows operators to see when they are given cues to play a CD, turn on a microphone, or take some other measure necessary. Given these two bits of information, only now can one look at sound booth locations.

Location
A booth can be located in one of three areas: in the wings of the sanctuary, on the second story (such as a balcony), or on the ground floor.

A quick answer for where to add a sound booth is “place it out of the way and build it in a wing.” Great idea? Bad idea. Based on what you've just read about line-of-sight, the wing qualifies as a bad location.  
 
Depending on the setup of your sanctuary, you might have a balcony or room adjacent to the rear wall of the sanctuary. Here's where the upper area may or may not be the best location.  A balcony that is well aligned with some main speakers and provides a line of sight to the pulpit/stage area can work.  Some churches have used the adjacent second story rooms and knocked a huge hole in the wall. This is not an ideal location, as the main speakers will never be pointed directly at the second-story section of the wall, so the sound quality coming into the booth won't be the best. Next, you need a big hole for sound to enter and to see the stage.   

If you build a booth on the ground floor, it should be located in the back, so the congregation is between the booth and the stage. The booth operators should be facing the pulpit, having direct line-of-sight across the congregation to both the pulpit/stage area and the main speakers. I recommend elevating the booth floor 18 inches. An easy way to measure the correct elevation for your booth floor is the ability to see the stage if the congregation is standing and you are sitting in the booth. 

By the way, you might get the argument that wearing headphones makes any location acceptable.  However, headphones don't take into account general room noise (even people sitting still make noise) and sound dynamics of the room. 

Security
If someone breaks into the church, they can/will break into the sound booth. Therefore, sound booth security should be based around securing the booth from “honest” people. Who are those "honest" people? 

1. People who use the area outside of normal service times such as home school groups or weddings. They might assume they have free-reign if it's not secured. Anyone using the sound booth should be properly trained. Therefore, train one or two adults from the home-school groups or have a call list of booth operators who are willing to work outside of Sunday mornings.   

2. Youth group kids who think it would be cool to hook up their gaming console to the main screen on youth night. Again, not that it's inherently bad, but they should have a trained individual set up their systems for such usage. Images of a 32-ounce drink hovering over the mixer make for nightmares.   

3. Finally, the most dangerous of the "honest" people...kids. They think it’s neat to sneak into the sound booth and play with the knobs and switches. I figure it like this...if I get a phone call that the church was broken into, I'll expect the sound booth is now missing a lot of equipment. Outside of that, there is no reason to see signs of an untrained person in the booth such as mixer knobs in weird settings or equipment laying all over.

Secure your sound booth with a door lock. Then, only provide trained people with keys.

Building the Booth
How big should the booth be? Much of this answer depends on how much space is available in your sanctuary. You need a countertop big enough for a mixing board (around 28 inches). Then you need room for a comfortable swivel chair.  Then you need room to move around. Bottom line is this: give yourself room. Tape out a section on the floor and see if that gives you enough space. 

There are now two basic types of booth to build: closed and open.  A closed booth is one in which there is a large window opening that can be opened and closed as well as a lockable door. This is a lot of work to build and rather costly.  The pros are a secure environment for protecting your goods. The cons are the openings have to be high enough to permit line-of-sight to the mains. Also, securable window closures are expensive.

An open booth has limited security but the trade-off is maximum visibility. The open booth design is also more aesthetically pleasing than a huge box in the sanctuary. 

Chris Huff is the owner of Behindthemixer.com, a Web site for church sound system operators. It is also a resource for churches and their research into sound systems.