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DIY PA | Tannoy

As installation contractors of commercial PA / 'Tannoy' and Background Music (BGM) systems, we have a wide range of knowledge and experience against all types of commercial environments and customer installations. We would consider many smaller, basic and traditional Public Address (PA) / 'Tannoy' and / or Background Music (BGM) applications to be DIY capable by electrically knowledgeable tradesman and end user customers.

Traditional Public Address (PA), Tannoy and BGM System

Background

Note: Please use as a guide only for traditional commercial audio applications - assumes basic electrical / technical knowledge.

Most (if not all) public address / tannoy audio systems will employ three primary functions:

These functions are discussed throughout this guide.

Design Specification & Audio Application

What audio application do I want from my system?
Typical traditional public address (pa) / tannoy audio applications are designed for making voice announcements. However, some systems also employ additional audio applications (most notably, background music BGM when the system is not broadcasting voice announcements). In such cases, an infrequently used pa / tannoy system will require a different system design specification to that of a system that also employs background music. One example of this difference would be loudspeaker design and qty / numbers. Generally speaking, volume output from a pa / tannoy audio application is high and deemed 'intentionally intrusive'. As background music is usually 'on' continuously, it is generally set at a lower level so that discussion and communication activities within the local setting can continue unhindered. To help make this distinction and to enable lower level audio but quality audibility, a background music audio application is likely to have a higher density (qty) of loudspeakers when compared to a pa / tannoy only application. 

Do I need a mixer?
A mixer connects (takes in) different audio inputs and 'mixes' the audio for a combined output (generally connected to an amplifier). A mixer is also likely to apply some audio conditioning and also raise microphone levels (pre-amp). Do you need a 'mixer'? Well, if your system design only requires a single microphone input then it may be possible to couple this directly to an amplifier. However, as most amplifiers will expect a certain impedance and signal level, we would advise against this. Separate mixer units and popular combination mixer / amplifier units are available.

What about the amplifier/s?
Your amplifier/s will provide the basis of audio 'power' delivery from the system input/s, and out to the speakers. In 'size' terms, amplifiers are sold with a power rating, specified in watts. Generally speaking, you should correlate the power requirements of the amplifier directly to the power demands of the speakers which are also specified in watts.

Tip TIP: To avoid overload and stress to the amplifier and to ensure product longevity, allow for a margin of 'headroom' capacity when specifying your amplifier size. Always refer to specific manufacturer requirements. Our advice is to allow for at least 20% headroom capacity for voice PA / announcement applications and at least 30% for BGM / radio applications.

What 'Input/s' will you require to you system?
Your audio application requirements will likely dictate your inputs (eg. if your pa / tannoy system only requires voice announcements, then you are likely to want a microphone/s). If your application is for BGM or Radio, then you will need to consider input capability of the mixer / amplifier as well as the associated input source (ie. radio tuner, music player). You can of course combine these applications.

How many speakers do I need?
The most frequently asked question we receive. Every installation and project is different, all will have their specific requirements and challenges.

Tip TIP: We have all heard the result of a single, large speaker that has been poorly positioned... knock your head off for those close by and poor audibility at distance, not good design. Allowing for a good number of speakers, strategically located, means that we can keep the overall levels down, whilst providing quality coverage and output intelligibility.

What type/s of speakers do I need?
Commercial audio systems are fundamentally different to stage, performance and typical home audio systems. For most installed commercial audio systems, the amplifier output is a high voltage (up to 100volts in the UK) to afford efficient long distance audio transmission over relatively small cable sizes. Commercial audio speakers have line transformers built in to them to step down the voltage. It is therefore very important that you attach the correct speaker type to the system. The speaker size in terms of audio output (dB) is important - but the design is really up to you, the installation surface, location and of course the aesthetics. Consider also the environment, specialist speakers may be required (eg. weather-proof, anti-vandal, ATEX).

Installation Guide

Equipment Location?
Consider the location of the main system equipment. Cables to the speakers will need to be installed from this location, is there cable containment to use? is there easy access to and from this location to install cables? If you intend to input radio to the system is there external access to install the aerial, perhaps select a location with an external wall.

Speaker Volume Settings and / 'tappings'
Commercial audio speakers are line driven from integrated transformers. The secondary side of these transformers usually have selectable 'tappings' (eg. a 6watt ceiling speaker might have tappings for 6, 3, 1.5 and 0.75 watts). Using these tappings, you can set individual speaker volume level output, ie. higher tapping for noisy areas, lower for quiet areas.>
What type of speaker cable should I use?
Amplifier output to speakers can run at up to 100volts in the UK. We would therefore always recommend using a double insulated cable, installed within cable containment or locations to protect it from mechanical damage.

What size of speaker cable should I use?
The size of speaker cable is determined by the power output and the distances to the speakers (see chart below).

How do I connect the speakers?
Commercial audio speakers are wired connected in parallel (see diagram below).

Speaker Wiring Diagram PA / Tannoy Speaker Cable Size

Volume Levels and Controls
The mixer / amplifier controls the power delivery to the speakers. It will likely have multiple input levels control and a single output control (master). By adjusting an individual input (eg a mic input) you can alter the volume level associated with this input (ie. microphone announcements are louder or quieter, but other inputs remain unchanged). The amplifier will also have a 'master' levels control which adjusts all volume levels. Remember you also have the speaker transformer 'tappings' to control the levels of individual speakers.

Tip TIP: You can install a volume attenuator controller to provide for further individual volume control to one or many speakers.

Audio Zones or 'All Calls'
Most commercial audio systems simply present output to all of the speakers (ie. the announcment or music goes to all speakers, we call this an 'all calls' system). It is possible though to configure and design a system to create audio 'zones' so that you can control output to individual speaker groups (this could be to separate office areas from the factory or even segmenting the system into separate floors or different buildings. Zone design and configuration can be complicated - for this reason, we view multi-zone commercial audio designs (PA/Tannoy or BGM) as beyond the scope of a basic system, and would recommend you contact us to discuss your project design and plans further.