This article will discuss that essential piece of equipment that can let a whisper be heard by a thousand people – the public address system.
The purpose of the public address system is to amplify sound and project it with sufficient quality, volume and direction to cater for all members of the assembled audience. Public address systems can be employed at any event where the volume of a performance is not sufficient for the entire audience to hear. This consists of indoor and outdoor functions, live music, conferences, DJ events and sporting events.
A public address system consists of a number of important components all of which have a specific part to play in the overall operation of the system. In this article we will discuss some of the main components that make up a PA system working our way through the system from the start point of the audio to the final reproduction of the sound to the audience.
Microphones: The purpose of a microphone is to pick up an audio source such vocals or musical instruments and convert it into an electrical signal. This signal is then transmitted down cabling or via a radio transmitter/receiver unit to a mixing console. Microphones can be found in a variety of shapes and sizes to cater for different applications. A large scale live music event can easily employ over twenty on-stage microphones, many of which will be specifically designed to cater for their particular application. This may include hand held vocal microphones such as the Shure SM58, drum kit microphones such as the Sennheiser E604 and radio systems such as the AKG WMS series which allow use of wireless handheld or headset microphones. To achieve the very best sound quality it is important that the correct microphone is employed and whether you are buying or renting it is always worthwhile doing as much research as possible to ensure you get the correct microphone for your particular requirements.
Mixing console: A mixing console is made up of a number of channels into which audio signals such as vocals or musical instruments are directed. The size, equalisation, balance and output volume of each signal can then be changed to generate a ‘mixed’ single master output signal which will then be transmitted to an amplifier. Mixing consoles also enable each channel to be sent to auxiliary outputs which feed on-stage monitor speakers or effects units. Mixing consoles differ in terms of the amount of channels, the quantity of auxiliary outputs each channel possesses and more recently in terms of analogue or digital systems. You should decide on the most appropriate mixing desk for your purposes in terms of these factors as well as of course your budget.
Processing equipment: Digital audio processing equipment allows the user to alter or modify the audio signal in a variety of ways to make it more controllable or more pleasing to the ear. Regularly used processing equipment includes graphic equalisers which allow the user to increase or decrease the gain of individual frequency ranges, audio limiters which restrain a dynamic signal within an assigned gain range – particularly useful for signal of potentially variable size such as vocals or drums and gates which close a particular channel when the signal level drops below a user defined level. Not all types of audio processing equipment are necessary for every type of event and once again it is sensible to research the different units available and decide if you will use the features of the equipment enough to justify the expense.
Amplifier: A power amplifier takes a low level audio signal, replicates and converts it to a much larger signal which is sent to loudspeakers where the signal is converted back into sound energy. An amplifier needs to be powerful enough to drive your speakers and produce the appropriate level of sound but not so powerful that much of the amplifiers potential is wasted. Be aware that if you are using an amplifier that has a power rating greater than that of your speakers that it is possible to blow the speaker cones if the output level of the amplifier is not carefully monitored. Again research into compatible speaker and amplifier combinations for your particular requirement will ensure that you end up with an appropriate PA system at the first time of trying. Mixing desks are available with built in amplifiers. These are most suitable for smaller events and are ideal for performers who move their equipment on a regular basis.
Front of house speakers: Audio loudspeakers convert the electrical signal provided by the amplifier back into sound energy and project it to the assembled audience. There are different loudspeakers available to cater for different frequencies of sound for instance sub-woofers that cater for extremely low range sounds for example bass guitars or kick drums and tweeters that project high range sounds such as vocals and cymbals. An effective public address system will have the most suitable speaker components to project the full range of sound being channelled to it. Active speakers, which have amplifiers built in, are commonly available. These negate the requirement for a separate amplifier unit and have the benefit of perfectly matched amplifier and speaker combinations. You should decide on the most appropriate combination of speakers for your requirements in terms of size and weight if you intend to move them regularly, the maximum number of people they will have to cater for and as with everything else, expense.
Stage monitors: Stage monitors or foldback are floor mounted speakers that face the performer allowing them to hear themselves on a potentially noisy stage. The signal is provided from the mixing desk via the auxiliary feed and as with front of house speakers they require amplification which can be from an external or in-built amplifier (known as an active monitor). The positioning of the monitors is important if they are to provide sufficient and natural on-stage sound and to reduce the likelihood of feedback. It is also recommended that the volume of the stage monitors be kept as low as possible. Ideally each performer will have their own monitor and monitor mix but this is not always possible due to space or budget restrictions. That said always try to buy the best monitors possible as a good sound on-stage will give the musicians the confidence to perform to their very best.
Cabling: The conduit that links all the components together, high quality audio cabling is one thing which will be commonplace at any event where public address equipment is required. You should always buy the best quality cables you can afford as they produce far superior sound quality than cheap cable and last a great deal longer.
All of these components need to be specifically selected to correctly cater for your event’s demands and therefore it is always recommended that you carry out in depth research and discuss your particular requirements with a specialist public address system supplier who will then recommend an appropriate system.
Advise your chosen supplier of the following aspects to make sure they can recommend the best PA system to cater for your needs:
• The type of events you are running.
• The maximum number of people the system will have to cater for and how they will be situated in the venue e.g. 1000 people standing, 200 people seated around tables.
• The number of on-stage performers
• How many mixing desk channels will be required
• The availability of power supply.
• The number of monitors and monitor mixes required
A high quality Pa system could be the difference between an event being considered a success or failure. As a result it is always worth investing time into researching the components that make up a system and the brands of equipment which are considered the best to do the job in hand. That way you can either hire or buy a sound system that suits both your requirements and budget.