PA systems lie at the heart of any good outdoor event. As a crucial component of meetings, conferences, parties and shows, both public and private, when the correct system is purchased, everything else naturally falls into place. It is very important for all new buyers of outdoor PA systems to educate themselves and research the available options, of which there are very many.
Outdoor PA System Overview
A PA (Public Address) system is an electronic system which includes a number of components working together to amplify sound. The components of a basic system include the sources, the mixer, the amplifier, the loudspeakers, and the monitors. For more complex systems, there are other components such as stageboxes, multicores, and DI boxes. The inputs (or sources) are typically microphones or musical instruments, which are, in turn, connected to the mixer. The control centre of the PA system, the mixer, is used to balance the audio levels and the tone of the inputs and to add special effects if needed.
Understanding the Outdoor PA System
Having a basic understanding of outdoor PA systems will help inform the buying decision.
PA Speakers and Monitors
There are two main types of speakers in the PA system - the front loudspeakers and the monitors – which are both connected to the mixer and powered by external or internal amplifiers. The front loudspeakers (also called front-of-house speakers) are what the audience hears, and the monitors are what the people on the stage hear.
For basic PA purposes and the lowest sound levels, monitors are not always needed, but for larger, louder events with lots of instruments, the monitors are very important for the people on stage to hear if the mixer is providing the correct levels and tone. PA loudspeakers and monitors should not be confused with backline speakers. Backline speakers are often instrument amplifiers (such as guitar amplifiers), and microphones are usually placed in-front of these speakers to send the desired sound to the PA system.
The simplest and most versatile PA loudspeakers are full range speakers, which supply both the bass and high frequency speakers inside the same speaker casing. In the case where sub-bass frequencies are needed, bass bin speakers can be used in addition to high range speakers. Sub-bass frequencies are below 80Hz and bass frequencies range roughly from 80Hz to 250Hz. Frequencies above this are in the mid-range of high-range.
Mixers are a vital component of any PA system and they serve many important functions. It is their job to raise levels of the input signals so that they may be processed, provide equalisation and tone management, and control the level of the outgoing signals to the amplifiers.
Cables & DI Boxes
PA systems are connected by two major types of cabling: balanced cables and non-balanced cables. Microphones are connected to the PA using balanced connectors, while direct inputs from other instruments such as guitars, keyboards and music players (such as jack-to-jack cables) are unbalanced. Mixers have two inputs –microphone inputs (balanced) and line inputs (unbalanced). Balanced inputs are usually XLR cables, with the female connecting to the microphone and the male to the mixer.
Unbalanced signals are never ideal, and this is why in the case of direct instrument feeds using unbalanced cables, it is necessary to use a DI box. The DI box takes the unbalanced input and converts it to a balanced signal, and the output is then suitable for connection to the mixer.
PA Stagebox & Multicore
It is sometimes best with outdoor events to monitor and mix the sound remotely, which is usually from the back of the venue behind the audience. A PA multi-core (a system of audio cables) and stagebox setup allows this to be done. The microphones and other inputs connect to the stagebox, and these signals then travel through the multicore to the mixer. The levels and tone are then managed with the mixer, and the signal is returned to the stagebox and on to the amplifiers and the speakers. Most multicores are available with between 12-24 microphone inputs and 4 return XLR/phone audio lines.
Outdoor PA System Considerations
There are a number of ways to gain a simple PA system, and this mainly depends on the type of mixer and the type of speakers. There are two types of mixers and these are powered and passive; a passive mixer requires a separate amplifier, while a powered mixer is a mixer with an amplifier included, which removes the need for a separate amplifier and can be connected straight to the speakers. Powered mixers are easier to manage and set up. There are also PA systems which have no dedicated mixer, instead using an amplifier with a mixer built-in. Mixer-amplifiers are another option for when requirements are very simple, but their limited functionality makes them a bad choice for live music.
Both monitors and loudspeakers can also be passive or powered – passive speakers need to be connected to a separate amplifier, while powered speakers come with an amplifier built-in. Passive speakers provide better flexibility with more possible PA options and better scalability, while powered speakers are simple and offer a cheaper alternative to purchasing a passive speaker/amplifier combination.
Power and Decibels
The wattage of the PA system generally governs how loud the system is, and the more wattage, the louder the system. The power is supplied by the amplifiers, and the power rating of the speakers needs to be lower than the power output of the amplifier to achieve the desired volume which the speakers are able to provide.
For the loudspeakers, the power rating is displayed as the RMS. This doesn't mean the maximum power output of the speakers, but the average power level that the speakers can produce comfortably (continuous power rating) – this is the rating to look for. PA systems should not run continuously at full power capacity, and this is why it is always a good idea to go for most watts possible for the price.
Outdoor PA systems need to be more powerful than indoor systems, and for any outdoor event, the correct power level will depend on the number of audience members, the distance of the audience from the stage, and the desired decibel level for the audience to experience. Small outdoor venues will require loudspeakers that can provide 100dB and amplifiers that supply at least 200W.
Choosing the Correct Mixer
Selecting the correct mixer for the task is often the most difficult part of buying an outdoor PA system, but aside from the choice between powered and non-powered mixers, there are a number of simple considerations to make the purchase easier. Line input channels cannot accept microphone inputs, though many modern mixers have microphone channels which accept both line and microphone inputs. Microphone channels with pad switches are also able to accept line inputs, which is useful for larger mixers where no line inputs are provided.
As large, powered electrical systems being used for events with lots of people, safety precautions always need to be taken when setting put and managing outdoor PA systems. For example, all mains power cabling should be in good condition, properly earthed and not present a hazard to others. All non-mains cabling should be able to supply the adequate amount of current. All equipment and cabling should be protected from water and the elements.
Buying an Outdoor PA System on eBay
To purchase outdoor PA systems on eBay, the first step is to go to the eBay homepage. Most audio components are found by following Sound & Vision, which can be found under All Categories. From here, click on the Home Audio & HiFi Separates link to go to the main audio listings page. This is where Speakers & Subwoofers and Amplifiers & Pre-Amps can be found under Categories, and each of these category listings can be refined using the search filters on the left-hand side of the listings, according to Type, Brand, Condition and Buying Format, for example, new outdoor speakers or mixer amplifiers.
There is no specific category for mixers or monitors. To find these on eBay, search for the appropriate items using the search box at the top of any eBay webpage, for example 'PA mixer' or 'DI box'. Bundled PA systems are a good choice for basic outdoor PA requirements, and these can also be searched for using the appropriate search terms.
Outdoor PA systems are central to all kinds of outdoor events and shows, and there is always a PA system available to match the needs of the user and to ensure that the event is a success. Always the most important thing to understand is how PA systems work and how they are set up, and it is advisable to use other in-depth guides and product manuals to achieve this.