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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
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
2,018 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
elgordo
530 posts
 
Don't worry about the slide rule, I think I still have one. It should be packed away with the eight track and the Elcassette.
jeffreybehr's avatar
jeffreybehr
805 posts
 
Here's the easy way to calculate resistances in parallel--use this http://www.1728.com/resistrs.htm site. Lots easier than having to use one's brain.

Speaker systems do NOT sound good when connected in series. I believe it has to do with all the signal driving the 2nd system having already run thru the 1st system's crossover. (However, it's plenty OK to connect drivers in series.) Connect the systems in parallel.

Lower impedances do not tend to cause amplifiers to oscillate, but one does need to be careful about the amp running out of current. That will happen only if you're trying to drive a quite-lo-impedance load quite loudly.
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