CHOOSING A PA SYSTEM FOR YOUR OUTDOOR EVENT

Whether it be a church fete, air show, fun run or corporate day a PA system can be an essential part of communicating with the guests and adds to the enjoyment and safety of the event.

You may be planning on setting it up yourself or want assistance from the professionals, in this article we’ve explained some of the key topics that we get asked about and given you enough knowledge to plan with confidence!

ONLY TWO LETTERS BUT SO MUCH MORE

The acronym ‘PA’ tends to be used fairly liberally nowadays and is generally interpreted as any sound system used for the amplification of voices, instruments or music playback. Being an abbreviation of Public Address, it originally described a system used for announcements in public buildings or spaces but has since become a generic term for any sound reinforcement system used for announcements, playback, live music or performance.

PA Systems are also associated with the term ‘Tannoy’ which is actually a brand name and the company that manufactures speakers and other associated audio equipment used in public buildings. It’s a bit like the whole Hoover/vacuum cleaner argument but a tannoy can be a PA system used for announcements but would never be something that a live band would play through!

When planning an outdoor event and thinking about the PA system it is worth considering what you need the system to do as there are two very different types of system that both have their advantages and disadvantages.

CONSTANT VOLTAGE PA SYSTEM

Constant voltage systems are also commonly referred to as ‘100V line speaker systems’ or ‘high voltage audio’ and in the US more likely ‘70v line speaker systems’. These all refer to the type of PA that uses a step-up transformer on the amplifier output and a step-down transformer within the speaker.

For outdoor use and in situations where sound needs to be distributed over a large area it is common to use horn type speakers. Horn speakers consist of a compression driver and a flared acoustic horn to direct the sound and although they may look a bit ‘old-school’ they can produce sound up to ten times more efficiently than cone loudspeakers.

As these speakers are lightweight, compact and relatively inexpensive it is possible to easily rig them on stands and poles so that they can project sound around the site. Cabling is straightforward too as many speakers can easily be linked together.

The use of the high impedance system’s step-up and step-down transformers allows for the speaker cable to be significantly thinner than that of a low impedance system. This may not seem like a big deal but when you are running out hundreds or even thousands of metres of cable over a large site the difference in both cost and practicality is huge.

Although there are many advantages of using 100v line PA systems, of course, there are also disadvantages too. To be fair, there is one important one that can be significant in certain situations. The frequencies that these types of loudspeakers can produce are typically between 300Hz and 10KHz. When you compare that to a full range speaker you are missing most of the bass and some of the high treble frequencies. This may seem like a big problem but the range they produce includes most of the frequencies produced by the human voice and in particular the range between 500Hz and 5KHz which is so important to the intelligibility of speech.

The limited frequency range means that the 100V line system isn’t suitable for situations where you need full range audio such as live music. However, it is ideal for events when the primary purpose is announcements such as Air Shows, Church Fetes, Country Shows, Corporate Team Days, Fun runs and any situation where a commentator or announcer needs to communicate with a large crowd.

We often get asked if it is possible to play music through the 100v line speaker system. Yes, it is, 100v line systems are commonly used for background music systems. However, you have to bear in mind that it will most noticeably lack bass and sound a bit thin. That might be fine for background music or the odd track but you wouldn’t want to use it if the music was the primary purpose..

LOW IMPEDANCE SPEAKERS

These are what you might recognise as the more ‘conventional’ type of speaker. They typically have a large cone that produces lower frequency sounds and also a compression driver and horn for the high frequencies. These speakers are designed to produce the full range of frequencies so are better suited for music and performance. In larger systems, the speakers can be arrayed and addition enclosures are used to produce sub-bass.

Some low impedance speakers are weatherised so are suitable for use outdoors or in other cases, it is possible to use covers that protect the speaker from the elements without affecting the sound too much.

Although you benefit from having high-quality audio with a full frequency range there are of course some drawbacks to using this type of PA system for your outdoor event.

Unlike the high frequencies which are very directional, the low bass frequencies radiate out in all directions so can get lost and people behind the PA will hear mainly just the bass. As mentioned earlier large cone speakers are pretty inefficient so high power amplifiers are required if you want to have chunky bass sounds.

Distributing sound over large areas is more problematic when using low impedance speakers. Long lengths of speaker cable need to have far bigger conductors and so can be expensive and impractical. If you distribute the audio at line level then you will need to provide power for amplifiers at each speaker location.

HORSES FOR COURSES

As you can see, there are pros and cons for each type of system and the choice of which is right for you really depends on the size and scope of the site that you are trying to cover and what you intend to use it for.

Many people get hung up on wanting a full range system because they may have a band playing at their fete or outdoor event but it is entirely appropriate to run two independent systems for this purpose. Ordinarily, you wouldn’t want the sound from the band to be blasted all around the site so having a local full range system for the band plus a 100v line speakers distributed around the site for announcements is the best solution.

IN SUMMARY

Including a PA system for announcements is such an important part of the classic outdoor event. Being able to tell the punters what is coming up on the programme, introducing the attractions and welcoming guests is a key part of a show and adds enormously to the audience’s enjoyment. Thankfully it isn’t difficult to achieve and organisers shouldn’t be put off from doing it by the cost or technicalities. The choices are easy to make and we have a range of packages available should you want to do it yourself. Alternatively, get in touch to discuss your needs.

If you need some help choosing the best equipment for your outdoor PA please get in touch using the details below.

CALL US: 01473 705205

EMAIL US: info@avunit.com

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