Does anyone rember how to calculate impedance?

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?

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

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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Jeffreybehr-I was giving advice to another Audiogoner. He is runnig a satellite system with two mini-monitors and two subs. It looks like there is no crossover for the subs. He essentially is running them in parrallel. He twisted the wires together and connected them to his reciever. I suggested he try running thme in series. I wanted to make sure he did not improperly load his amp. He says the speakers are rated at six ohms and his amp has selectable impedance. Sounds Like he is okay.
I learned this stuff years ago and forgot. It's not really a problem with the level of components I use. Thanks!