Intro to Sound System Electronic Components

The Electronics

Most sound-system electronic components have excellent frequency response, low noise (hiss) virtually no hum, and low distortion. Therefore, the main considerations are features (number of channels, etc.), cost, and reliability. Reliability is discussed in the next section.

The control board is usually called a mixer. It should have enough input channels for all of your present needs, plus about 25%. (An input channel is a set of circuitry and controls for one microphone or cassette deck or CD player, etc.) Standard mixers are available with anywhere from 4 to 48 or more input channels.

A mixer puts out about a 1-volt signal with only milliwatts of power. The component that provides the power for the speakers is the power amplifier. The power amplifier should have two channels if monitor loudspeakers are to be used. In some rooms where recorded music is to be used, a separate stereo-like system is set up for the music, and you then need three channels -- or four if there are monitors. Depending upon the design of the speakers, more channels of amplification may be needed. The power rating depends mainly on room size, loudspeaker efficiency, and the loudness of the music to be played in the room. Typical power ratings range from 100 watts for a small traditional church with efficient speakers to over 1000 watts for large facilities that use very loud music.

Since all rooms emphasize certain frequencies, an equalizer is needed to make the system sound natural and to help prevent feedback. Equalizers can boost or cut the energy fed to the speakers in different frequency bands. Most systems today use 31-band (also called 1/3-octave) equalizers. Having so many bands allows much greater control than an equalizer with 15 or fewer bands would give. In very good rooms owned by people with low budgets and very good loudspeakers, these less-capable equalizers can be used with good results, but anything less than 31 bands is a compromise. If monitor loudspeakers are used, a separate equalizer (or a two-channel one) is essential, since the monitors must be equalized separately.

For problem situations, there are computerized feedback-control systems that can help. While one of these may be needed for a difficult situation, they should not be a part of most initial system plans. However, your system designer should be able to warn you if one of these may be needed to complete your system.

The law (the Americans with Disabilities Act) requires many public performance facilities to provide a special hearing assistance system for the hearing-impaired. These systems are available from many excellent manufacturers at a fairly reasonable cost. Many houses of worship have chosen to provide such systems for their congregations, even though the law may not require them to do so. Basically, such a system is a small radio transmitter operating on a special frequency. Each person needing assistance uses a small receiver with either an earphone or an inductive loop for hearing aids that can use such loops. A very similar system using invisible infrared light rather than radio is also available.

Lightning and surge protection is usually a good investment for the sound system. There are many manufacturers making surge suppressors, but very few whose products provide optimal protection. In fact, there is only one that is certified by Underwriters' Laboratories. Look for this certification when you buy protectors.

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