► CommunityBlogMusic EDnet BlogApril 2017Designing a multi-use PA that's right for your school

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The Music EDnet blog provides all sorts of interesting information related to our work with teachers and schools around the country. But it also gives the EDnet Team an opportunity to put fingers to keyboard about broader issues that we believe may be of interest to teachers ... including the challenges that face us all from day to day.

Designing a multi-use PA that's right for your school

There is a myriad of issues to consider when designing a multi-use sound reinforcement system for a school. In this article we look at the process of designing a multi-purpose PA and offer some advice to help you avoid costly mistakes.

Designing the appropriate multi-use sound reinforcement system for a school is no easy task. There are many issues to consider and consequently there is no 'one size fits all' solution; but there are some simple steps to follow to help you avoid making costly mistakes.

What is a multi-purpose PA?

PA (or Public Address) and Sound Reinforcement systems come in all shapes and sizes, but all are intended to amplify or reinforce sound.

The term "PA" was originally used to describe an electronic amplification and distribution system with a microphone, amplifier and loudspeakers, used primarily for speech to "address" a large "public" ... such as public gatherings, sporting events, making announcements in travel terminals and so on.

Sound Reinforcement is a term used most often for systems designed primarily to amplify or reinforce the sound of live performances (of all kinds) and music to an audience and typically includes mixing of multiple microphones and other sources and signal processors, for both effect and control.

Both "PA" and "Sound Reinforcement" are often used interchangeably and opinions vary as to how they should be differentiated ... i.e. by intended use or by the sophistication of the technology.

A well designed system will be suitable for a range of purposes and locations, from choir and ensemble performances to school assemblies, from sports days and general mobile PA to chapel and multi-purpose halls. Such a system is typically housed and maintained by the music department, but should be a general school resource, and as such, should be funded outside of the normal music budget.

What components are included in a multi-use sound reinforcement system?

While there will be some variation in specific components reflecting the requirements of individual circumstances, a typical system will include:

  • mixer
  • powered speakers (or amplifier with passive speakers)
  • speaker stands
  • wireless mic system
  • microphones
  • microphone stands
  • cables
  • mobile rack to house components

The mixer

From small to very large, analogue or digital, mixers are an important component in any live sound reinforcement system. Sometimes called a sound board, mixing desk or console all audio mixers are primarily designed to combine signals from two or more sound sources (such as microphones, electronic instruments, and recorded audio devices) and send the resultant "mix" to amplifiers and speaker systems.

Digital mixers are now very affordable and becoming increasingly popular and offer incredible flexibility in terms of signal routing, signal processing (eg many include parametric EQ, compression and noise gates on each channel as well as digital processors and EQ on all mixing busses) and convenient memory settings, on-board stereo recording, remote control (eg via iPads and laptops) and multi-channel recording.

When choosing the mixer, one of the most important issues to consider here is, 'will the system be used for teaching purposes?' e.g. VET pathways (Aus) or SOND units (NZ). If so, then it is generally best to choose a mixer with traditional analogue inputs, as it is much simpler to track the signal path and demonstrate the various processes the signal goes through from input to output. Digital mixers on the other hand, can offer greater functionality, such as the ability to record live performances and retain multiple "scenes" (different mixer configurations) for quick and easy recall, but can be more complicated to operate... a much steeper learning curve for the uninitiated.

In many cases, the best option is a hybrid mixer, which combines analogue connections with the power of digital tools. A hybrid mixer will also facilitate live recording of your performances, so are a great option for schools wanting to record choirs, ensembles, assemblies and so on.

If the system is to be used purely for mixing purposes, i.e. not for teaching, then a rack-mount digital mixer with integrated remote control using iPad are becoming increasingly popular. This will allow you to monitor and adjust the mix from the middle of the audience, without the need for cumbersome and often costly wiring.

The speakers

In order to fulfil the "multi-use" aspect of the system it is likely that various speakers will be used, depending on the application. For example, a chapel or hall scenario may require permanently installed wall-mounted speakers, while an outdoor ensemble performance a pair of portable powered speakers on stands would be used. In addition, fold-back speakers may be necessary... these are stage-facing speakers which allow the performers to monitor their sound. The fold-back speaker system can also be used as the main speakers for smaller audiences. And for more intimate settings, a single speaker with microphone connected directly will serve as a simple PA. 

With the advent of digital speakers, the weight of the typical speaker has significantly reduced... many 15" powered speakers weighing well under 20kg. This make them useable in a school environment, where OH&S considerations are most important. 

The microphones - wireless + wired

A wireless mic system is composed of a transmitter and a receiver. The transmitter can be contained within the microphone itself, or worn as a body-pack with the microphone attached to it. Wireless microphones generally come in the same variety as wired mics:

  • Hand held - the most common type, where the mic and transmitter are a single unit. The better quality systems include popular good quality “capsules” such as Shure SM58, Sennheiser E835, AKG D5 and so on.

  • Lapel or Lavalier - clip on mics that plug in to a separate body-pack transmitter.

  • Headset - worn on the head or over the ears and the capsule is reasonably close to the mouth. These are best performing for hands free operation and are also available in miniature, skin toned forms for theatre productions. Plug in to a separate body-pack transmitter.

The receiver is then rack-mounted in the roadcase.

When evaluating the most suitable wireless system for your school, the most important thing to determine is "How many mics will we need to use simultaneously?" This is particularly important in the case of the multi-purpose PA as it will likely be used to reinforce the sound for everything from a single-person speech to a jazz choir, from a multi-instrument ensemble to a theatre performance. A suitably designed multi-purpose PA will cover all of these scenarios.

More info regarding wireless mic systems in the EDnet Library here - www.musicednet.com/ED00008

In addition to the wireless mics, which are generally used for voice amplification, you will also likely be using a range of wired mics, for individual instrument or ensemble sound reinforcement. For miking up instruments amps and drums you would use dynamic mics; for miking up a choir or ensemble from a distance you would typically use a paired set of condenser mics.

More information regarding the different microphone types available here - www.musicednet.com/ED00009

It is worth noting that reinforcing choirs can be quite challenging and requires careful mic placement and correct setting of gain structure through your mixer. A useful guide to miking choirs is available in the EDnet Library at www.musicednet.com/ED00002

Bringing it all together

For convenience, portability and safety, we recommend all components be housed in a mobile rack case. The case will house the mixer, whether pop-up or rack-mount, and allow ample space for the rack mounted wireless microphone system(s) and include a utility drawer for wireless mics etc. On-board power would  also be included allowing quick and easy connection to a single power point.

A couple of completed examples:

Multi-use PA with pop-up mixer

Multi-use PA with rack-mount mixer

Choosing or designing a live sound system does require some specialised knowledge and we recommend you contact Music EDnet. We have considerable expertise and experience in designing, supplying and installing systems of all sizes ... and can provide the training and support to ensure you and your colleagues are able to use the system effectively.


19/04/2017 2:10:44 PM | 0 comments
Filed under: multi-use PA, Music technology news, PA, Sound reinforcement

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