100 Volt Line Systems
Wiring a large number of speakers in a venue can be a real headache using standard amplifiers and 8 ohm speakers, you might have to use parallel series wiring or multiple amplifiers. It is far easier to use a 100volt line system, with this system the installer can daisy chain a large number of speakers to one amplifier, as long as the power of all the speakers summed is not greater than the power of the amplifier. It is usually better to be within 90% of the amplifiers power so as not to overheat/overdrive the amplifier.
100 Volt line PA systems are used in many types of venues like offices, schools, places of worship, warehouses and shops. These systems do not need to be installed by qualified electricians, the installer just needs to be a competent installer for audio systems. They are very easy to install as long as you do all the necessary calculations and plan your cable runs well.
100 Volt line speakers do loose some of their dynamic range, but the easy installation far out ways this, and the sound produced is more than adequate for background music and announcements.
100 Volt line amplifiers use a transformer to convert the amplifiers high output to high impedance. The speakers have transformers attached as well, these have various tapped input connections which take the required power from the amplifier, these could be 2, 4, 8, 15, 30 watts, for example. This is useful for two reasons, one so you do not go over the amplifiers max power (stay within 90%) and two, some areas in the venue can be set at lower power. This allows some zones to be quieter, i.e. a bar area may need to be louder than the toilet or dining areas.
Remote volume controls (attenuators) can also be used, these can be installed in different zones and one can be used for each speaker if required, giving the user complete control. These have power ratings too, so the installer will need to add the power of the attenuators together instead of the speakers it is connected to, to figure out the correct amplifier rating. Some amplifiers have these in built-in to give volume control over different zones.
So in short the real advantages to 100 volt line systems are:
- Powering a large number of speakers from one amplifier.
- The ability just to parallel wire each speaker in the chain.
- Use very thin cable for long runs.
- For a basic system, only one pair of cables needs to be routed back to the amplifier.
- Ability to tap different power ratings or use external attenuators to lower the volume.
Here are some wiring examples of how to use a 100 Volt line PA system
A This shows a system with three 20 watt tapped speakers, so the sum of these is 60 watts, the very minimal power amplifier you could use would be about 54 watts. If you only had 60watt amplifier you would need to tap one speaker down to lower the total power to around 54watts.
B This diagram shows the speakers tapped at different powers so they stay within 90% of the amplifiers power
C If the speakers go over the 90% of the amplifiers power an additional amplifier may be used to drive the remaining speakers.
D This diagram shows an 80 watt 100volt line amplifier with 4 zone outputs. Each zone has its own volume control. Check the amplifier manual to see the max output for each zone, normally it would be the amplifiers power shared across the 4 zones. So in this example the max for each zone would be 20 watts, so you would need to be within 90% of that. The diagram shows each zone with 15 watts of speakers, so this falls under the amplifiers maximum power.