Yamaha receiver does have a choice between 4 and 8 ohms. I also use that same Yamaha at times with a pair of Polk 8 Ohms inside. When using the inside speakers, they are all thats on. Have outside set to Speaker A and inside to B. So I switch between the two. In this case would wiring the 4 outside speakers in "series" be better ? That way I dont have to fiddle with the Yamaha's menu and change the "ohm" setting all the time ?
I'm not 100% certain, but I think running 8ohm speakers on the 4ohm setting should be fine. The opposite, running 4ohm on the 8ohm, would
not be ideal because the speakers will draw more current than expected. So I would think setting to 4ohm for both 8 ohm Polks and 4 Ohm Yamaha's in parallel would be fine
when run individually.
Bear in mind, though, that if you play
both the indoor and outdoor speakers at the same time (have both A and B selected) -- either on purpose or accidentally -- I think that is internally running both A and B speakers in parallel -- and 8 ohms in parallel with 4 ohms would be 2.67 ohms, which would not be ideal, even on 4ohm setting.
You could run the Yamaha in series for 16 ohms -- that should be fine for the amp, it will just play a little quieter. I have done this for two center channel speakers -- I didn't want to risk 2 6 ohms speakers in parallel, so I ran them 12 ohms in series and it works fine. I didn't notice a huge volume difference, but I used center channel volume adjustment on AVR to balance volumes (<- volume balancing would be needed for your stereo speaker setup).
I feel pretty confident on all of the above, but hopefully somebody can confirm (or correct) that 1) 4ohm setting is fine for 8ohm speakers; 2) A+B = parallel wiring of A and B speakers; 3) Running 16 ohm is no issue.
