THREE WAYS TO IMPROVE INFERIOR SOUND
By: Bruce and Jenny Bartlett
Feed back is something you want from thoughtful church members after your sermon, not from your speaker system during it.
Good news: You don’t have to put up with bad sound. Good audio equipment set properly will eliminate many sound problems. And skilled sound system operation is not as difficult as it may look. Here are some professional tips to know for yourself and to pass along to your sound technicians.
WHAT THE KNOBS AND DIALS DO
To make your sound system work for you, it helps to know out the names and functions of its parts.
*Mixer: An electronic device that controls the volume of each microphone and sends their signals into one composite signal. A mixing console is a large, elaborate mixer.
*Module: A group of mixer controls in a vertical strip that affect a single microphone.
*Input section: The part of the mixer that receives signals from microphones or other sources.
*Output section: The part of the mixer that sends a combined signal to an audio amplifier.
*Trim, gain, or input attenuator: A knob or control used to turn sound up or down to prevent distortion (a gritty sound caused by the microphone signal coming into the mixer too strong.)
*Clip or peak light: A light on the input module that flashes when the incoming signal is too strong and thus is causing distortion.
*Fader: A sliding volume control for the microphone plugged into that module. Note: Some mixers have rotary volume controls called pots (short for potentiometers.)
*Master faders: Faders on the output section of the mixer that control the overall volume of all the microphones. Note: Some mixers also have group or submaster faders, each of which controls a group of microphones-say, for a choir.
*Meter: A device that shows how strong the mixer output signal is.
*Power amplifier: It boosts the signal coming from the mixer so it is adequate to drive the loudspeakers.
Now that we know the terms, we can tackle common problems in church audio systems.
MIXING A GOOD BALANCE
Correct mixer settings let the congregation hear a good mix, but wrong settings make the mix odd and unnatural.
How to set up. To prepare the system, follow these steps in order:
*Zero or neutralize the mixing console by setting all controls to off, flat, or zero. Reason: This establishes a frame of reference and avoids surprises later.
*Set your power amplifier volume controls about halfway up and turn on your equipment. Suggestion: Turn on the power amplifiers last to avoid mixer turn-on thumps.
*Set the master faders (and submaster faders, if any) to design center: the shaded area about a third down from the highest fader setting. Reason: This minimizes mixer noise and distortion.
Adjusting the mix. The faders can now be adjusted to obtain a good mix: a pleasing balance of loudness for all the mikes. Key: You want each of the sound sources to be heard at a natural-sounding level.
Note: Generally only a limited number of mikes needs to be mixed at a given time – the minister’s mike alone, or several choir mikes, for example. Tip: For best clarity, turn down microphones not in use.
What to do: Find the best fader settings for each sound source during a sound check or, if necessary, at the beginning of the service. Tip: Mark the settings with a grease pencil or tape. You can adjust the faders around these marks as needed during the service.
Note: When adjusting the sound, never bring up any fader so fast that the congregation notices a sudden change, or so high that feedback occurs. Suggestion: Mark the feedback point on each fader, and take care not to exceed it.
Leveling the extremes. A compressor automatically turns down the volume when sound gets too loud and turns it up when it gets too quiet, thus evening out extreme volume changes. Example: The compressor makes a guest speaker who alternately yells and whispers easier to listen to.
How to use it: Connect the module’s access out jack to the compressor’s in jack, and then connect the compressor’s out jack to the module’s access in. Next: Adjust the compressor’s controls:
*Ratio or slope control to 3:1 or 4:1.
*Threshold control to -10.
*Gain reduction control (if any) to the point that the loudest speech is not unpleasantly loud.
NIXING NOISE AND DISTORTION
It’s important to set the input faders so that the level reads about 0 on the mixer meters during the loudest part of the program. Reason: If the meter level is too low, you’ll hear mixer noise (hiss). If the level is too high (into the red area), you’ll get distortion (a gritty, raspy sound).
Suggestion: To do this, adjust all the input faders up or down by the same amount. Keep the master faders at design center for the least noise and distortion. Note: You can also turn up the power amplifier for more volume.
Next step: The clip light and trim controls are your allies in fighting distortion. Method: During the sound check, have the minister speak as loudly as he or she will during the service. If the clip light for the minister’s mike flashes, there’s distortion. Turn down the trim control to just where the clip light goes out. Reason: That’s the optimum setting for a clean signal.
Tip: Set the trim control on each input module separately, turning down the other microphones so they don’t interfere. Note: Unless your setup changes drastically, you can forget the trim controls once they have been set.
Caution: Never turn up your system so loud that the power amplifier clip light stays on. Reason: You can damage your loudspeakers.
Feedback-that hollow ringing or loud squealing sound-is caused by a vicious circle of amplified sound being picked up by microphones andreamplified over and over.You can reduce the possibility of feedback by:
*As much as possible, placing microphones behind the loudspeakers. This breaks down the feedback path.
*Adjusting the faders so that the volume is loud enough to be heard, but not loud enough to cause feedback.
*Turning down the faders on unused microphones.
*Installing an automatic mixer, which turns off all microphones not in use. When someone speaks into a mike, it turns back on. Alternative: Use gated microphones that turn themselves off when unused.
A FINAL SOUND CHECKLIST
In judging the quality of the sound system and your mix, ask these questions:
*Loud enough? The amplified sound should be loud enough to be heard comfortably. Prerecorded back-up music should be as loud as a real musical ensemble.
*Clean? Is the sound free of hum, buzzes, hiss, distortion, and feedback?
*Clear? Is speech easy to understand?
*Good tone quality? Are deep notes from the organ, bass drum, or bass guitar full but not boomy? Are highs crisp but not sizzly? Are voices natural, not bassy, thin, or muffled?
*Good mix? Can you hear each voice or instrument clearly? Is any element too loud or too quiet?
(The above material appeared in the January/February 1992 issue of Your Church.)
Christian Information Network