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Does anyone rember how to calculate impedance?

In the old days when amps and receivers had only one set of speaker outputs, if you wanted to to run more than one pair of speakers you either had to run them in parralell or in series. This varied the amplifierload. Say if I were connecting two eight ohm speaker in paralell, what load would the amplifier see? If I connected them in sereis what load would the amplifier see? The person with the correct answer will receive a vintage slide rule.
gregadd
elgordo
530 posts
 
For speakers in parallel it's R1 X R2 divided by R1 + R2, where R is the speaker impedence. So two 8 ohm speakers would be 8X8=64 divided by 8+8=16 for an answer of 4 ohms. In series it's additive so two 8 ohm speakers would be 16 ohms.
slv
87 posts
 
Parallel Load = (Load A x Load B)/(Load A + Load B)
Series Load = Load A + Load B
gregadd OP
574 posts
 
You guys are genuises! So in order to avoid potential damage to the amp, it is better to connect them in sereis? Lower impedance is more likely to cause the amp to oscillate.
P.S. I was kidding about the slide rule. However, if you insist, Where can I find one?
aball
2,016 posts
 
You will have load-sharing problems if you connect them in series because not all 8-ohm speakers have the same impedance curves. I would not recommend it. If you amp is tough, hook them up in parallel. Arthur
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