A mixer-amplifier has inputs for a microphone, music and often Bluetooth, USB or a radio built in. It is the whole system in one box, and most shops and offices only need one. A plain amplifier (sometimes called a slave or power amplifier) only makes a signal louder. Use one when you already have a mixer, or to add more power to a large system.

100V line is for running many speakers from one amplifier over long cable runs: shops, pubs, warehouses, schools and offices. Add up the watts of every speaker (each 100V speaker has a power setting, for example 6W) and choose an amplifier with at least 20% more. Low impedance (4 or 8 ohm) is for a few speakers close to the amplifier, such as a home, a bar or a meeting room, and gives the best sound quality for music.

As a rough guide, one ceiling speaker for every 15 to 20 square metres in a shop or office with a normal ceiling height. For louder rooms, outdoor areas or warehouses use wall, horn or column speakers. Our packages already include the right number of speakers for the room size they state.

Public counters, receptions, places of worship and meeting rooms should offer a hearing loop for people who use hearing aids. Choose a loop amplifier by the floor area it covers (for example 300 or 600 square metres).