The Top Six Church Audio Questions for 2012

Contributor: Tim Vear

One of the ways that we zero in on what you want from us is to check in with Senior Applications Engineer and Shure Answer Man Tim Vear.

Not only is he a featured speaker at countless workshops and seminars, he wrote the book on Audio Systems for Houses of Worship which many of you probably have in print or digital form.  This booklet is constantly in update mode, explaining its fifteen versions.  So far.

Tim, who can describe the physical characteristics of wavelengths and make it both understandable and interesting, was the lucky fellow we tapped just a few days before Christmas to share some of your most recent church audio-related questions and concerns.

Here are the top six, not only from his phone, email and online encounters with you at Shure headquarters, but from his recent audio seminars at Worship Arts Technology Summit and other events.

How do I mic the congregation (for recording or broadcast)?

Generally, it's desirable to have some direct pickup of the congregation to add ambience and energy to a recording or broadcast of your service.

The usual technique is to treat the congregation as a very large choir: place one (or two for stereo) microphone(s) above and somewhat in front of the congregation.

Just as for choir applications, a flat-response, cardioid condenser microphone is recommended. Aim the microphones at the faces of the people and away from the main PA speakers as much as possible.  This will insure that the resulting sound is mostly from the audience and not from the PA.

During a broadcast, the sound from these microphones can be brought into the overall mix at the desired level, typically lower when the pastor or worship leader is speaking and higher for musical sections, particularly when the congregation is singing.  For recording, it's sometimes useful to record the congregation mic(s) on separate track(s) for sweetening of the final mix.  Note that the congregation mics should NEVER be routed to the main PA mix.

How can I pick up individual congregation members who need to speak? 

If you're trying to pick up the sound from an individual congregant, it may be possible to use the technique above - but ONLY for recording or broadcast.  Since the congregation mics will usually be at some distance from any individual talker, the engineer will have to bring up the level of the nearest mic to pick up that source. Even then, the sound quality from the distant microphone is likely to be poor.

A better technique is to bring a microphone (usually wireless) close the individual. This requires a microphone "wrangler" (and sometimes multiple microphones) to get the mic into position quickly.  Just as for other close-up vocal applications, a shaped-response, cardioid microphone is recommended.  If you plan to amplify the congregant in the main PA, then ONLY the close mic technique will work.  A distant microphone (greater than a couple of feet away) cannot achieve usable gain-before-feedback when it's amplified through the main PA system.
 

Why doesn't the pulpit microphone sound the same as a lapel or headset microphone?

The reason that these microphones have different sound qualities is almost completely dependent on the distance from the microphone to the mouth of the talker.  The closer the microphone, the better the signal-to-noise ratio, the better the gain-before feedback, and the better the low-frequency response (for directional microphones).

The signal-to-noise is improved because the level of the voice increases by 6dB each time the mic-to-mouth distance is cut in half while the background noise stays constant.  The gain-before-feedback is improved in a similar manner, resulting in either higher level with the same feedback potential or the same level with lower feedback potential.  The low-frequency response is improved because the closer placement increases proximity effect for a directional microphone.  Overall, a close microphone placement will give significantly better performance, particularly in live-sound applications.

Is it safe to use a wireless microphone in a baptistry?

Sometimes there's a need to use a microphone in a "wet" environment such as a full-immersion baptistery.  Although a properly grounded sound system and baptistery installation should be safe even for use with a wired microphone, a wireless microphone eliminates any possibility of a ground-fault that might be hazardous to the wearer.

The only suggestion would be to protect the microphone and/or transmitter electronics from direct contact with water as much as possible.  Such contact is not dangerous, but the microphone (particularly a condenser type) and/or the transmitter may stop working if water intrudes into the mic element or the electronics.  There are waterproof pouches and even waterproof microphones that can be used in this case.

Can I use rechargeable batteries in my wireless systems?

Rechargeable batteries can be cost effective and environmentally friendly alternatives to single use devices.  The principle considerations are the operating voltage, the run-time, and ultimate lifetime capability of the rechargeable.  Here's how the different types of rechargeable and non-rechargeable batteries compare.  
 

 The table above gives typical capacities of popular 9V batteries.[/caption]
 

 The table above gives typical capacities of popular AA batteries.[/caption]

These characteristics depend on the specific chemistry of the battery.  For transmitters that use AA batteries, both nickel-metal-hydride (Ni-MH) and nickel-cadmium (Ni-Cd) types may be suitable.  Though they have somewhat lower operating voltage than alkaline types (1.2 V vs. 1.5 V) their run-times are fairly similar.  However, for 9-volt size applications, the run-times are much less than with the equivalent alkaline.  For this reason, we suggest using a Lithium-polymer (Li-Polymer) chemistry.  This battery has an operating voltage and run-time similar to an alkaline 9-volt type.  Note that the Li-polymer chemistry is not available in AA size cells.  Any of these batteries should be used only with their specific chargers and operated with regard to manufacturers suggestions in order to get the maximum life.

A properly maintained rechargeable should be capable of up to 500 charge/use cycles.

Are directional antennas always the best choice for my receivers?

Directional antennas are usually recommended for specific applications only.  These include operation over long transmission distances (greater than 150 feet) and/or operation in the presence of localized interference sources.

Directional antennas typically exhibit increased sensitivity in one direction and less sensitivity in other directions.  The most common directional antenna is the log-periodic type, often called a "paddle" antenna because of its shape.  In the direction of increased sensitivity, the antenna can deliver a stronger signal to the receiver, which can increase the effective range of the system.  At the same time, the antenna can offer some rejection of interfering signals coming from other directions.

However, most directional antennas are wideband devices.  They are equally sensitive to all frequencies in their operating band.  This means that a directional antenna aimed at an interfering source will increase the level of that interference as well as whatever desired signal may be in that same direction.  Finally, too much antenna sensitivity (gain) may result in overload of the connected receivers.  This can aggravate intermodulation and actually desensitize the receiver.  For most applications omnidirectional antennas are still the norm.

Download the current edition of Audio Systems Guide for Houses of Worship right here.