This subject is quite a wide one, and one that causes a lot of problems as there are lots of ways to connect speakers up and a lot of ways to get it wrong!

The first question we ask is "How many speakers do you want / need to run?" If the answer is 2 or 4 then it's easy as a standard 2 channel or stereo amp will work fine, and theses amplifiers like the Adastra A2 are also available in 4, 6 or 8 channel versions so that you can run 4, 6 or 8 speakers off one unit as their are 4, 6 or 8 amplifiers in one box.

But if you need to run, say 30 speakers, then what do you use? It would be relatively expensive to have lots of amplifiers for this instance, so the solution is a distributed line system, also known as a 70v or 10 volt line system.

How this works is that the amplifier output is connected inside the box to a step up transformer, and each speaker has a step down transformer with variable wattage settings, or tappings on the transformer with say 1 watt, 2 watts, 4 watts etc.

If you have a 100 watt amplifier; then with a distributed line system then you can run say 100 speakers tapped at 1watt, or 50 tapped at 2 watts. As long as you don't exceed the maximum wattage of the amplifier, you should be fine, although as a matter of good practice, you should really limit the load on the amplifier to 80% of the rated wattage, so we would recommend say 80 speakers tapped at 1 watt for instance.

With this type of system, you can also run long lengths of cable, as the resistance of the cable (all cables have a resistance) has less an effect on the volume as the voltage that the speaker system runs at is higher, but as the wattage is the same the current is less and the losses are the square of the current. So less current = less losses!

All the speakers are connected in parallel. Typical resistance of a speaker is 8 ohms, but with the transformer it can be hundreds of ohms depending on the tapping and so the load on the amplifier is lower the lesser numbers of speakers are connected. Quick fact: a 15watt tapping has an impedance of 666 ohms.

We use an impedance meter which has a chart supplied so when we check an installation, we can instantly see if there is a problem on the system as there is a direct correlation between the impedance of the system and the apparent wattage load. It puts out a tone so you can hear if there's a faulty speaker on the system, so we can see if it needs replacing.

If you need an installation or a service job in the North West of England, please call us on 01204 385199 or email orders@hwaudio.co.uk