Engineering notes
How 100 V public address differs from low-impedance speakers
100 V lines for long floors and many speakers. Ohm systems for a meeting room near the amplifier. Do not mix on one channel.
Two families, do not cross-plug
A 100 V (or 70 V) line uses a high-voltage amplifier and a transformer on each loudspeaker. Long corridors, many speakers, modest cable. A low-impedance (8 Ω, 4 Ω) system is for a meeting room — short cable, few speakers, high watts each.
An 8 Ω speaker on a 100 V line, or the reverse, burns the speaker or the amplifier. Add tapped watts — not the maximum on the price list — and leave 20–30% spare on the amplifier. ELV