Producing clear sound is vital in houses of worship to ensure that a message reaches the congregation. While loudspeaker selection is of obvious importance in the delivery of audio, you still need to have the right amplifier to power them. Here are a few factors to research before choosing a new amplifier.

Before even looking into the speakers that you have, think about the house of worship itself. It may have best equipment that money can buy, but a major factor that contributes to sound quality is the room it’s installed in. How big is the sanctuary? Does the system need to be transported before and after the service?

With small spaces, not a lot of power is needed, however, confined spaces can create problems with sound quality and acoustics. The bigger the venue, the more equipment is required to deliver sound reinforcement, and volume and projection should to be taken into consideration. If more power requirements are needed, you may need more than one amplifier.

If the sound system needs to be completely set up and pulled down before and after a service, a light, compact amplifier that is easy to configure is essential. ‘It’s worth considering the application that the amplifier will be used for,’ comments Waring Hayes, technical brand manager at MC2 Audio. ‘In an installation, for example, the necessity to work reliably over a wide range of mains voltages isn’t important, but an amplifier for touring would be much more useful if it was capable of worldwide operation and tolerant of mains fluctuations (such as operating on a festival site running from a generator alongside a load of lights).’

An important factor to consider is the power rating on both the amplifier and speakers. Each amp will have an RMS power rating which is the power it puts out. Wattage needs to be looked at as well, to see how much the speakers can handle. Ideally, choose an amp that delivers twice the power of a speaker’s power rating. For example, if a speaker’s rating is 350W, the amplifier needs to output 700W. It is better to overpower than to underpower. The more power created, the more control and less distortion there is. If a low-powered amp is plugged into a loudspeaker at a high volume, the loudspeaker can be damaged. However, if you have a high-powered amp, volume levels can be higher without the amp struggling with its load.

Hayes adds: ‘Consideration has to be given to connecting speakers in parallel – two of the aforementioned speakers will handle 1,000W between them and so the amplifier in this situation needs to be capable of providing a minimum of 1,500W. There is also the impedance to consider when running speakers in parallel as this reduces according to a simple mathematical relationship, but the power output of an amplifier is always specified for a given load impedance.’

As a safe rule, it is better to choose an amp that is from the same brand as the speakers. Although amps and speakers are often compatible with one another, it’s best to check this before investing. Some amplifier brands are owned and developed by associated companies and can provide power to the speakers without causing damage. ‘Many speaker companies will specify certain amplifier and processing combinations to work best with their speakers, and additionally provide the required settings to achieve this,’ explains Hayes.

Mike McCormick, senior regional sales manager at AtlasIED, backs up the point: ‘Our products are designed to optimise the performance capabilities of other relevant AtlasIED products. The amplifiers are engineered to take advantage of the full frequency response that our speakers offer, allowing you to get the best sound possible.’

Headroom is the term for the difference between the normal operating level of an amplifier and the maximum amount that an amplifier can pass without distortion. By using an amplifier with extra headroom, the speakers should produce a clean and undistorted signal. If there isn’t enough headroom, the gear will be frequently distorting the audio. There are many professional amplifiers that are equipped with additional headroom. In order for these to work at an optimal level, the amplifiers must be set up with a speaker or set of speakers with the same power rating.

Impedance is a measure of resistance and is an important factor to consider as it will determine the compatibility between an amplifier and a set of speakers. Both amplifiers and speaker will have a unit of resistance which is measured in ohms. Ideally, speakers need to have a higher impedance than the amplifier. If the amplifier has low impedance and puts out more power than it can produce, then problems will occur. To check this, look for the ohm rating on the speakers and divide this by the number of speakers. For example, two 8Ω speakers will require an amplifier with 4Ω.

This represents how much background noise an amplifier creates. A signal-to-noise ratio is defined as a level of signal power to the level of noise, which is measured in decibels (dB). The higher the numbers in the ratio, the better the specification. To get the best out of your amplifier, choose a product that has a strong signal-to-noise ratio.

Amplifiers are classified according to their underlying circuitry, typically ranging from Class-A to Class-D for most uses. As a general rule of thumb, audio quality is highest in Class-A models and lowers as you move down the alphabet. However, Class-A amplifiers preserve the full linear audio signal at the detriment of power efficiency. So, while audio quality may dip as you go from Class-A to -B, -C and -D, efficiency will rise and running costs will lessen.

Class-D amplifiers are typically seen as the best of both worlds for many applications as they reach efficiency ratings of up to 90% with little compromise on the resulting audio quality. They operate different to their preceding classes in that they employ a form of pulse-width modulation known as switching for controlling output devices and are usually smaller than other amplifiers. In comparison, Class-A amplifiers can have a low efficiency of as little as 40%, making them well-suited to low-power applications requiring the best quality, such as a guitar amplifier.

There are additional amplifier classes to be aware of: Class-AB amplifiers, which are often more affordable than Class-A and combine the features of both Class-A and Class-B models; Class-E and -F, designed mainly for radio-frequency applications; and Class-G and -H, which are built to offer enhancements to the design of Class-AB amps.

If you can, try to test an amplifier before buying it. You will be able to check that your speakers are compatible and find out whether there are any issues before investing. ‘Along with optimising performance, ordering and troubleshooting any potential issues working with one manufacturer helps streamline that process,’ says McCormick.

Researching amplifiers is an important task and, when done properly, ensures that houses of worship receive good quality sound for their services.

This article was first published in the January-February 2020 edition of Worship AVL. Subscribe at www.proavl-central.com/subscribe/worship or read on Issuu.

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