The next time you walk into your sanctuary, carefully listen to how sound carries in the room. Clap your hands and listen to what happens. Do you hear a smooth decay of sound, or is it quite "dead" sounding? Worse yet, do noticeable echoes bounce around like a racquetball court?

I've been in church sanctuaries that were a nightmare to mix in because discrete echoes were nearly as loud as the original sound source. That makes for a very confusing sound. The problem in those cases is usually the acoustical design of the room, although it can be made worse by improper choice and placement of the speaker cluster. But take heart. The worst case I ever heard of was described by Don & Carolyn Davis at one of the SynAudCon seminars I attended. They told us of driving through the Midwest and seeing a church that appeared to be a concrete dome in the earth. That's what it turned out to be. The "designers" found this large mound of earth, poured concrete over it to form the "roof" of the church, and then dug away the dirt underneath it to form a bowl shaped seating area. The experience of entering the building was one to remember. Two people simply walking together down a ramp into the sanctuary was enough to excite the entire room so much that one feared it would collapse on them. The echoes of the room almost seemed to be amplified. Needless to say, this situation proved unusable for church services.

Well, we're not here to talk about acoustics. This time I want to talk about the use of signal delays and reverb units in a church service. We'll talk about some of the acoustic origins of these sounds, what past and present technology allows us to do in simulating those effects, and then how to tastefully approach their use in your church services.

God's Creative Use of Effects

One of the first and most prominent sounds you are likely to hear is an echo. Maybe you've heard the repetition of a person's words as he calls out in a large canyon. As we stand beside him, we will first hear the sound of his voice directly to our ears. Moments later, we will hear his voice repeated after the sound wave has traveled across the canyon and back to our ears. There is a delay to that sound caused by the time it takes for the sound to travel (at roughly 1,130 ft/sec) out to the canyon wall and back to our ears.

This same type of delayed echo of a sound occurs in a room as well, and is caused by the sound reflecting off of surfaces in the room and finding its way back to our ears. We will hear the original sound as a reference, and that is followed quickly by the early reflections or echoes. (It is possible for sound to arrive at our ears before the direct sound does, because sound can sometimes travel through the structure of a room faster than through the air. This could be called a pre-echo, and becomes a matter of great importance in the proper design of recording studio control rooms.)

How apparent those echoes sound is relative to how loud they are and their arrival time. The loudness is a function of the material it happens to reflect off of. This can also alter the frequency content of the sound, since that material may reflect certain frequencies quite well and yet absorb others. The arrival time back at the listener's ears is a function of how far the sound had to travel through its reflected path to arrive at our ears, and is of course relative to the arrival of the direct sound.

Some reflections may not even be able to be heard, even though they can be measured and proven to be quite loud by comparison. If the sound is delayed in time less than about thirty milliseconds, our brain will not perceive it as a discreet echo. So, reflections arriving less than thirty milliseconds after the direct sound arrives might be considered early reflections. Reflections that arrive thirty milliseconds or so after the direct sound arrival will generally be heard as discreet echoes. This effect is typically more noticeable with sounds that have a percussive attack, and this is why clapping your hands is an acceptable method of examining your situation.

When you clap your hands in a large enough auditorium, you may notice a smoothly decaying sound that lingers for a moment. This is know as reverberation, and is made up of many hundreds of reflections arriving at the listener's ears, so closely spaced in time that he cannot perceive them as separate echoes, but rather as a homogeneous mixture of all of them. Each room will have it's own reverberation "sound", determined by the acoustics of the room. That is to say, the manner in which the room is constructed, how large a room it is, if the surfaces are hard or soft, reflective or absorbent, even whether they are painted or not, and so forth, give the room its character - part of that character is the sound of the reverb. For example, a large room with a great deal of soft absorbent material may attenuate the lingering high frequencies of the reverberant field rather quickly while the lower frequencies of that reverberant field carry on longer. "Proper" design would present a reverberant field that is quite diffuse, with all frequencies decaying smoothly together, with no one frequency louder than another.

Electronic Effects Processors

Today, any of these acoustic properties of rooms, big or small, reverberant or not, and even those of the canyon wall, can jump into the sanctuary at the touch of a button. The ever diminishing price of digital technology has brought forth a plethora of affordable digital effects processors. Offered by a host of different manufacturers, digital effects processors are typically multi-talented, in that they may be capable of simulating literally any of the effects described above along with a long list of other, more imaginative or not-exactly-natural-on-the-planet-I-know-and-love effects.

Rather inventive techniques to simulate acoustic environments have been available for years. It's not my intent to go into the history of these devices here, but we should look at a couple of prominent devices from past technology.

Properly built, one of the best room simulators is an echo chamber. And that's exactly what it is, a room simulator. It is a highly reflective or "live" sounding room constructed to provide controlled reverb on demand. This echo chamber room will have one or two high quality loudspeakers placed inside it, and one or two high quality microphones as well. When the recording engineer wants reverb on his project, he simply sends a feed down the proper buss on the console, and feeds the audio signal to an amplifier connected to the speakers in the echo chamber. The sound then washes around the room, reflecting off the many surfaces of the room, and is picked up by the microphones. The signal from those microphones is then brought back into the "echo return" inputs of the console, or a couple of mic inputs, and fed to the stereo mixdown buss so that it can go onto the mixdown tape and be heard over the control room monitors. The engineer has access to the chamber so that he can reposition the loudspeakers and/or the microphones to shape the kind of reverb sound he wants for the project.

Notice that the effect obtained is properly termed "reverb", not "echo" - just one of those audio terminology quirks you should know about. In fact, sometimes silkscreen grammar on the face of today's consoles will have a buss labeled echo send. This was really always intended to describe an auxiliary buss used to send a signal to an effects device, and most often the device used was for reverb, not echo.

This effect is still in demand today. If memory serves me right, I believe it is Capitol Records' recording studios that have some of the best sounding echo chambers in Los Angeles. And they even rent time on them to other studios. Let's say you are doing an album project across town, but you want to get that Capitol Records echo chamber sound on your album. You can call them up in advance and arrange for the use of one of their chambers. The effects send from your console is fed via high quality telephone lines to their chamber amplifier, and the microphone signals are then returned to your studio's console via more high quality telephone lines.

One studio I have worked in a few times has their echo chamber built directly above the control room. If you happen to drive the signal to the chamber hot enough, you can actually hear the acoustic spill from overhead. It's a rather interesting sensation to say the least.

Another excellent device is a reverb plate. The better quality ones sound so good that they are still in use today alongside the more flexible digital effects processors. The theory is similar to the echo chamber - the sound from a speaker is picked up by one or two microphones. However, with the reverb plate, the "room", if you will, is a sheet of metal. The speaker is actually a specially designed transducer virtually attached to the plate near its center. When an audio signal is fed via an amplifier to this transducer, it causes the plate to vibrate. Those vibrations are picked up by two contact microphones attached to the plate in optimum locations. The signal from those mics is then carried back to the console and used just as described above. The cost of a reverb plate, just as any audio gear, varies with quality. A reasonably good sounding device, like the Echoplate, might cost under $1,000, while the better quality EMT plates used to cost as much as $7,000 - and that was ten years ago.

The spring reverb gained popularity early on because of its low cost. Until recent years, any electric guitar amplifier or electronic organ available had an inexpensive spring reverb unit inside. Now those are starting to be replaced with inexpensive but better sounding digital units. With this device, the signal from the console effects buss feeds a small internal amplifier, which then feeds an "electrical signal to mechanical torque transducer". This vibrates the spring in response to the audio signal, and that vibration is picked up with a "mechanical torque to electrical signal transducer" on the other end. Better devices would have occasional tie points along the length of the spring to provide added reflection points. This would make the "reverb" sound more complex and less like a spring. The inherent drawback of this design is that it cannot handle transients very well. Anytime a strong piano chord, or especially a snare drum sound hit the spring unit too hard, it would cause the spring to go BOING. Obviously this destroys the realism of the effect you are trying to create.

Different methods have been tried for years to delay an audio signal for a moment and then allow it to be heard. One brute force method was simply to attach a midrange driver at one end of a long tube (so long it had to be coiled in order to be practical), with a microphone placed at the other end to pick up the sound. Hardly considered flexible, this device found its best use as a signal delay for underbalcony systems, improving intelligibility for those farther away from the central cluster.

Another delay device was the early Echoplex, which simply used a small audio tape recorder and a moveable playback head to alter the length of time before the "delayed" signal was heard. Analog delay devices also gained popularity by eliminating the tape. These devices use a simple "bucket brigade" technique - the signal is stored very briefly in an analog "memory", and then released. By chaining several of these memories together, the signal can be held for quite a while. And by providing different points at which to "tap" the chain, a more complex output signal can be achieved. Many of these devices sound quite good, and still have their use today. The major drawback in both of these systems is first noise, and secondly limited bandwidth.

Of course, the buzz word of today is the digital effects processor. They were introduced in the mid '70s, and although they offered simpler operation and a unique sound, they were out of reach of most people at $7,000 to $12,000 each. Thank God that computer technology has marched onward, and now excellent quality devices that rival or even supercede those early ones can be had for a fraction of the price.

With the digital device, the analog audio signal from the console is fed through an Analog-to-Digital converter (ADC). This converts the signal into numerical representations of its voltage, polarity, and frequency. Once this conversion has taken place, the device can be read by the internal computer circuitry. It is then processed through a complex set of instructions which may alter its frequency response, feed it through various delays, and then recombine those sounds.

Right before the output, the signal will undergo another conversion, this time from digital to analog by going through a DAC. Many of these devices even direct slightly different types of sounds to separate left and right output channels, which help the impression of room simulation. If you think about it, if you walk into a reverberant auditorium and shout thanks to God, your voice is mono - but you hear the result in stereo, thanks to your two ears and God's fun with physics.

The limiting factor on many of the early digital units was bandwidth. They would only go as high as 10 kHz to 12 kHz. Of course, the argument is that natural reverb rarely contains frequencies above those limits due to the natural friction of air which dissipates the higher frequencies. Still, the desire lurks inside of every engineer to create some rather extraterrestrial effect, and advances have been made to increase that bandwidth.

Their other limiting factor was that the sound was often "grainy" - one could easily hear the "stepped" sound of the digital conversion. But here again, advancements have been made in sampling rate and smoothing techniques that make the current group of devices quite astounding.

Using Effects Processors Tastefully

Quite literally, whenever I am mixing an album I imagine a place where this performance is taking place, and then use the effects processors to help shape or define that place. Similarly, doing a sound reinforcement mix to me is really just mixing the album in front of an audience instead of in a small control room. As long as the room is large enough and relatively well-behaved acoustically, I approach the use of digital effects processors in exactly the same way as during a mixdown session.

Remember, a little bit goes a long way. Don't overdo it! The secret to their tasteful use is to listen very closely to your favorite albums. For worship music, listen to the Integrity's Hosanna! Music tapes and you'll hear very tasteful use of effects. Carefully analyze how they achieved that sound, and then simply emulate those ideas into your own services.

The only way you will ever become adept at using these devices is to read the operator's manual - y'know, that book that's still in the box somewhere - and then experiment with them. Now I'm guilty too. I often operate by the motto - when all else fails, read the directions. So learn from my shortcomings and do what I teach. The time to experiment is first on your own, then during rehearsals. Then apply what you've learned in a deliberate, creative effort during a service, many during the midweek service first to get used to it. The unspoken caution here is, don't experiment with the effects during a service, at least not until you are very comfortable with the device and know what your are doing with it. Even then, approach its use with care.

One good way to force yourself to learn the unit is working with a singer and accompaniment tapes. Whenever I am in this situation, I listen to what the original track is doing with regard to the lead vocalist's effects. Then I listen to the accompaniment track by itself to see what delays and reverb sounds are still there. And finally, during rehearsal I'll try to enhance the singer's voice very much like the original recording did. With those effects happening, and with the track loud enough over the system to be realistic, the end result is quite believable.

One more comment regarding the use of these effects. When the song is over, be certain that the delays and reverb are OFF before the pastor or anyone, including the vocalists, begins to speak. It's terribly embarrassing to hear a long, repeating delay of the pastor's voice thanking the vocalists for their musical offering.

Well, hopefully this has helped. We can summarize the acoustic effects this way:

Reverberation - many repetitions, becoming more densely spaced with time.

Echo - one or a few discreet repetitions of an audio signal.

Delay - the time interval between a direct signal and its echo.

Decay - the time it takes for echoes or reverberation to fade away.
And we can summarize the different techniques available for simulating these techniques this way:

Echo Chamber - In effect an "acoustic" means of creating an artificial reverb by setting speakers in a large room and picking up the resulting sound with microphones.

Plate Reverb - constructed of a large sheet of metal or foil which is suspended from its corners. It has a small speaker mounted on the sheet which makes it vibrate, after which two microphones pickup the resulting vibrations. Known as the brightest and most popular type.

Spring Reverb - A cost effective unit. Less expensive types are often characterized by a "twangy" sound.

Analog Effect Devices - Electronic devices which use a bucket-brigade circuitry to provide signal delays and reverb sounds.

Digital Effects Processors - Rapidly becoming the new standard. An all electronic device which offers the most control and variety of reverberation sounds, e.g., room simulation.

Don't be afraid to use effects in your service. Tastefully applied, they can bring new depth and dimension to the sound of your music. And most importantly, have fun!