When installing a 100V line system, it is important that the correct size of cable is used to connect the speakers to the amplifier. The following chart gives an indication of what should be used:
As the voltage on the line can approach 100 volts, installation must follow best practice with double insulated cable being used. Cable runs should be kept away from any potential source of interference such as 3 phase mains, data, telecom cables etc.
100V line line systems must always be wired in parallel and the total load presented to the amplifier must not exceed the rated output of the amplifier or damage can result
100V line loudspeaker switching In order to ensure that there is no breakthrough it is necessary to use the circuit below when switching 100 volt line loudspeakers either in groups or individually. The loudspeaker is not only isolated from the line but also shorted to itself in the 'off' position thus excluding any possibility of breakthrough.
100V Line Volume Controls These controls are specially designed for 100V line operation and simply wired in-line (in series) between the speaker and the amplifier. The maximum power ratting of the volume control must be observed and not exceeded, otherwise damage to both control and amplifier can occur.
Low Impedance Some amplifiers in the Adastra range have the facility for connection of low impedance loudspeakers. Low impedance installations require heavy cable feeding the loudpseakers to minimise losses and short cable runs are recommended. Where it is intended to use multiple low impedance speakers to cover an area, the speakers must be wired in a series/parallel arangement in such a way as to present the correct load to the amplifier.
Note: The total load impedance presented to the amplifier must never be below the rated amplifier impedance, otherwise damage can result. To avoid damage to the speakers the total power of the driver units should be at least 30% higher than the rated power of the amplifier.
You must NEVER mix 100V line and low impedance speakers on the same system.
Horn speakers are typically used in noisy environments, outdoors or areas that are quite large in size. The main disadvantage with this type of speaker is that they cannont reproduce music at all.
General installation considerations
- DO NOT run microphone cables near mains, data, telephone or 100V line cables
- DO NOT exceed 90% of the amplifiers output power when using 100V line (speech only)
- DO NOT exceed 70% of the amplifiers output power when using 100V line (high level background music only)
- DO NOT use re-entrant horn loudspeakers for background music unless the loudspeaker has been specifically designed for this purpose
- AVOID jointing the microphone cable, when this is unavoidable make sure a good screened connector is used, e.g. XLR
- ALWAYS use a balanced or floating low impedance microphone terminating into a balanced input on long microphone cable runs
- ENSURE that all loudspeakers are in-phase
- ENSURE that there are no short circuits on the loudspeaker line before connection ot the amplifier