GAI-Tronics Speaker / Horn Installation for GAI-Tronics Communication System - Manual (Page 4)

Pub. 42004-135H
Speaker/Horn Installation for GAI-Tronics Communications Systems Page 4 of 8
f:\standard ioms - current release\42004 instr. manuals\42004-135h.doc
03/15
Distributed Amplifier Systems
GAI-Tronics Page/Party ® and SmartSeries systems do not use speakers with line matching transformers.
The voltage on the wiring between the speaker(s) and the associated amplifiers is less than 15 V
RMS
, which
qualifies as National Electrical Code Class II wiring. Therefore, conduit is not required except for
physical protection. Cable distance should be as short as possible to reduce power loss. GAI-Tronics
recommends that the cable distance between a speaker and its associated amplifier not exceed 30 feet
(9.14 meters).
Indoor Cone Speakers
Depending on the amplifier and speaker combination used, an indoor cone speaker’s volume control and
speaker can be damaged due to the application of excessive power. In order to minimize the possibility of
such an occurrence, use the following set-up procedure:
1. Turn the amplifier volume control to its lowest output level before applying power to the system. Set
the speaker volume control (if applicable) to its maximum output position.
2. Measure the dc resistance of the speaker using a volt-ohm meter. Read the wattage rating of the
speaker and perform the following calculation:
Multiply the resistance of the speaker (Rspkr) by the speaker’s wattage rating (Wspkr), and find the
square root.
This number is the voltage (rms) limit from the amplifier to the speaker that should not be exceeded.
Vrms Wspkr Rspkr
 
limit
3. Apply power to the unit, and connect a 1 kHz @ 1.5 Vrms signal into the amplifier via the page line
with a voltmeter across the speaker terminals. Adjust the amplifier volume control until the voltage
limit is reached.
4. The speaker volume control may then be used to reduce the speaker level to the proper listening level
as changing conditions warrant.
N OTE : Using this procedure does not guarantee that damage will not occur to the volume control or
speaker since there are other variables, but it does minimize the possibility.
Central Amplifier Systems
Central or power amplifier systems are generally designed to use a driver with a 70 or 100 volt, line
matching transformer. The speaker’s power level is determined by the tap settings on the transformer.
Use of these transformers allows the speakers to be placed at long distances from the amplifier without
significant power loss (see Table 1 below).
The number of speakers connected to a central amplifier system is limited by the power available from
the central amplifier. The sum of the speaker power settings must not exceed the total available from the
amplifier. For example, a 250-watt central amplifier can drive 30 speakers tapped at 7.5 watts.
Table 1 illustrates the correlation between the wire size and the distance that speakers with integral
drivers or horns with separate drivers can be placed from a central amplifier.