High-Impedance And Low-Impedance Connections; Multiple Speaker System Drive Capability - Yamaha MA2120 Setup Manual

Appendix

High-Impedance and Low-Impedance Connections

For a high-impedance connection, a speaker transformer that raises the impedance to several hundred or thousand ohms is added to
the speaker system. This allows the speaker system to be effectively driven with much lower current than is required for a low-impedance
connection. Therefore, a large number of speaker systems can be connected. Even over long distances, there is very little transmission
loss due to the cable resistance being negligible in relation to the impedance of the speaker system. High-impedance speaker
connections usually operate at a specific maximum power amplifier voltage of 100 or 70 volts.
The more orthodox low-impedance connection does not use a speaker transformer. The speaker systems are directly connected to the
power amplifier with a rated impedance generally around 4 - 16 ohms. For short distances over which cable resistance is insignificant,
low-impedance connections deliver a sound quality that is superior to high-impedance connections.
The differences between connection methods are explained as follows.

Multiple Speaker System Drive Capability

High-Impedance Connections
As long as the total nominal power input rating for all speakers is within the power output capability of the amplifier, any number of
speaker systems can be connected in parallel. The power input rating is determined by the speaker systems and speaker transformers
used. It is also possible to connect speaker systems that have different input power ratings. In the case of speaker systems that are
capable of changing their input power rating (Yamaha VXC and VXS series, etc.), this can be utilized to vary the volume of each speaker.
Low-Impedance Connections
When connecting multiple low-impedance speaker systems to a single channel, the following methods are possible.
Parallel Connection
When multiple speaker systems having the same impedance are connected in parallel, the total impedance becomes the individual
speaker system impedance divided by the number of systems connected.
Serial Connection
When connected in series, the total impedance is simply the sum of the impedances of the speaker systems connected. However, if one
speaker system happens to fail, the electrical signal will not be passed on and subsequent speaker systems will be affected.
18
MA2120 Setup Guide
Speaker transformer
70V/100V
10W 10W
4Ω
8Ω 8Ω
Total impedance = 4Ω
4Ω
Failure
No sound
4Ω
Interruption
10W 10W 10W
Cannot be connected
8Ω
Total impedance = 8Ω