This depends on the loudspeaker load, i.e.: 20 x loudspeakers tapped at 5 Watts = 100 Watts For Voice Alarm, the amplifier’s rated power output should be at least 20% greater than the initial design for the loudspeaker load. Therefore, in our example, 20 x 5 Watts = 100 Watts + 20% = 120 Watts (our BV125D 125 Watt amplifier would be required).