Generally speaking...

Can I connect 2 sets of 8 ohm speakers (4 ohm load) to a single stereo output?

I have an A / B switch for my interior & exterior speakers, but I'd like to connect another set to my exterior speakers.

Thanks!

I've seen it done. Doesn't mean you should though

Completely depends on the amplifier. Some are rated to drive 4 ohm loads, some aren't.

If the amp is not rated to handle 4 Ohm loads, you can always safely connect the speakers in series creating a 16 Ohm load. As long the speakers are similar in design. The power will be shared resulting in lower volume levels though.

I don't think I'd want to connect speakers in series. Their impedance is complex function of frequency, and you will almost certainly get artifacts from the interaction of the speakers.

The amplifiers that were made to drive Apogees did very well into low-Z loads--the Scintillas dropped below 1 ohm, and had a reputation as amplifier killers. Pretty soon there were amps made to drive those loads--Krell, Aragon, I think maybe some of the Mark Levisons, and some of Nelson Pass' designs.

The question was general. I dont think we are talking high-end equipment here. But, maybe I'm wrong (It has happened before)

Yes that was some serious name dropping there....

Personally, I'm on some B&W's (C-4 towers)through a Rotel, very nice beginner set up.

To answere the question, YES, but I would suggest you check your amp for matching that load. If not, Russound has some impedance macthing speaker selectors and volume controls that will do the job nicely. (Low grade, no oxygen free copper contacts and whipes...)

Personally, I like Meyer, powered by Crest, driven by Gamble.. or the Meyer self-powered systems..

IIRC, some of the old McIntosh amps would drive loads down to 1 ohm (maybe even 1/2 ohm..)

You could also use a constant voltage (25 or 70v) system, depending on the number of speakers, power level, and length of the cabling.