Wednesday, October 26, 2011

Audio Systems

Probably the most obvious and most prevalent technological presence in the church today is the audio system. From small churches which simply want to amplify the minister's voice, to the mega-church with a 30-piece orchestra, 150-member choir, 4 balconies, and 15,000 seats, the PA (public address) system is a necessity in the modern church.

At it's simplest, the PA system takes audio from a few microphones, amplifies it, and sends it to one or more speakers. The intent, of course, is to make sure that each person in the audience can hear the message, announcements, songs, and other elements which are part of the worship service. A few simple additions allow for recording the sermon onto a cassette tape or CD for duplication and distribution to church members who could not attend due to illness or other absence, or to friends and family of members who might be interested in the content of the message.

As the size of a congregation and it's facilities increases, so too must the audio system. The largest churches utilize the latest in digital mixer and recording technologies to support dozens of microphones and instruments such as guitars and electronic keyboards which connect directly to the system; multi-channel speaker systems to support large worship arenas seating thousands; larger church campuses with worship audio piped to hallways, meeting areas, and nurseries; and multi-track digital recording systems to capture not only the sermon, but also all elements of the worship music, dramas, and other elements for wider distribution.

The principle which should guide the use of any church audio system is to enable everyone attending the service to participate in the worship of God. It should not be in your face, as it might be at a rock concert. The music group on stage is not performing for their own benefit; rather, it is leading worship. The focus should be on God, not on the singers or musicians, and the audio engineer must work to minimize any noise or feedback which would distract from worship.

But how does that work?

It starts with good equipment: quality microphones, sturdy cabling, a well-designed speaker system, and a good mixer console. Depending on the audio qualities of the worship space, additional outboard equipment may be required or desired to further process the audio signal and keep undesirable noise under control.

The mixer is the nerve center of any church audio system. At it's core, the mixer is simply a set of volume controls which control the sound levels of various audio inputs (microphones, guitars, CD or DVD players), then feed the combined audio to a final set of volume controls and out to the amplifiers and speakers. Most mixers also add equalizers to control specific frequencies through an audio channel, auxiliary outputs to send audio to stage monitors or hallway speakers, and additional outputs for external recorders or audio processors. These processors often include a compressor, which acts as a sort of automatic volume control for when a channel gets too loud; a gate, to essentially mute a channel as long as the signal is below a set volume threshold; or an effects unit that adds reverb, delay, or other "color" to an audio signal.

It's also common to run the output signal from the mixer into an audio processor before sending to the amps and speakers. Such a processor can match the sound from the mixer to the natural acoustics of the worship arena, keeping the overall sound under control and preventing feedback and other noise which can make speech or or vocals unintelligible. It can also take a stereo signal and spread it across a speaker array consisting of more than 2 channels, allowing both left and right portions of the audio to be heard throughout the room and helping to eliminate hot spots (too much volume) or dead spots (not enough volume).

As I mentioned earlier, another common use for any church audio system is to record the sermon. Most churches with smaller systems will simply connect a cassette or CD recorder to the stereo recording output of the mixer (sometimes labeled 2-track). The engineer then simply hits the Record button when the sermon begins, and Stop when it ends. The church will typically have some means of rapidly duplicating the master tape or CD in sufficient quantities for distribution.

However, many larger churches record their full services for later distribution. This use requires a much more complicated system, simply because mixing for a live performance is actually pretty different from mixing for personal playback. Rather than record a stereo signal based on the live mix, larger churches utilize systems which record each audio channel individually into a digital file. The engineer then plays back the raw audio and mixes it appropriately for playback in a home or car stereo system, portable CD player, or even a podcast. The reason the recording must be mixed separately from the live performance is that smaller-scale audio environments will sound completely different from the worship venue, so instruments and vocals must be balanced and equalized differently for those environments.

Additionally, really large churches often record video of their services in addition to the audio, and recording the full service makes it possible to dub clean audio over the edited video for a much better end result, which is important when distributing via DVD or YouTube.

Churches which broadcast live radio or television feeds of their services have an even more-complicated setup. They have to be able to simultaneously mix audio for the worship venue and for radio or TV. So they have 2 mixers, one for in-house audio and one for the broadcast feed, and a separate engineer for each. Now, if the church is using analog equipment, this can get very complex with microphone splitters, double or even triple the microphone cabling, and so on. But with the current breed of digital mixer systems, simultaneous live and broadcast mixing and recording becomes physically much less complicated. It is possible to connect all the audio to a single set of audio interfaces on stage, which digitize all inputs, then send this raw audio anywhere you want using very few cables: a mixer for traditional live environments; a different mixer for live broadcasts; and even a multi-track recording system for later mixdown and distribution. Once the audio is digital, live distribution occurs over Cat5 network cabling or optical fiber, and is completely lossless; that is, you do not lose audio quality when splitting and sending digital audio to multiple locations like you do with analog audio, and each link in the digital chain typically regenerates and rebroadcasts the data to remove any signal degradation that might have occurred due to distance. The possibilities are nearly endless.

The desired outcome of all of this is simply to allow as many people as possible to worship God effectively, while minimizing any noise which could interfere with that goal. It certainly doesn't hurt that we can now send sermons or entire worship services all around the world via the Internet, but that wouldn't be possible without the means to record it in the first place.

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