Yamaha XMV8140-D Owner's Manual download pdf (Page 30)

Appendix

XMV8280/XMV8140/XMV8280-D/XMV8140-D Owner’s Manual

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 system. That, in turn, makes it possible to

connect a larger number of speaker systems to each power

amplifier output. High-impedance speaker connections work at

a specific maximum voltage—usually 70 or 100 volts—and are

therefore also referred to as “constant voltage” speaker systems

(the label “constant voltage” is somewhat misleading: the actual

output voltage fluctuates according to the input signal).

For a low-impedance speaker connection, the power amplifier is

directly connected to a speaker system that has an inherent

impedance of 4–16Ω.

The difference between these types of connection are outlined

below.

 Multiple Speaker System Drive Capability

 High impedance

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 con-

nected in parallel. In a high-impedance installation, the

power input rating is determined by the speaker trans-

formers used.

If the 280W output XMV8280 is used with a speaker sys-

tem having speaker transformers that make the rated

input 10W, you can connect a speaker system with a max-

imum of 24 speakers per channel based on the calculation

(*), giving you a total of up to 192 speakers for the eight

channels. In a high-impedance installation it is also possi-

ble to simultaneously drive speaker systems that have dif-

ferent input power ratings.

(*) Yamaha recommends that you allow a 20% margin to

this number, considering variations in the trans-

former’s primary impedance, possible tap changes in

the future, and the addition of speakers.

 Low impedance

Normally only one speaker system is connected to each

amplifier channel, as shown in the diagram.

This means that the number of speaker system that can be

connected to an XMV is limited to eight.

However, even with low impedance connections, there is

a way by which multiple speaker systems can be con-

nected to one channel.

When multiple speakers systems having the same imped-

ance are connected in parallel, the total impedance

becomes the individual speaker system impedance

divided by the number of systems connected. This means

that if the XMV is set to 4Ω, up to two 8Ω speaker sys-

tems can be connected to one channel.

The second method is series connection. In this case the

total impedance is simply the sum of the impedances of

the speaker systems connected. But as you can see in the

series connection wiring diagram, if one speaker system

fails the second speaker system will be affected as well.

High-impedance and Low-impedance

Connections

10W 10W 10W 10W 10W

70V/100V

Speaker transformer

4Ω

8Ω 8Ω 8Ω

Total impedance = 4Ω

Cannot be

connected

4Ω

Interruption

Total impedance

= 8Ω

Failure

No sound

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