2 speakers with a nominal impedance of 6 ohms in parallel can drop below 2 ohms and Yamaha recommends 8 ohms min for A + B.
I've been trying to decipher these ratings in the service manual (thus my various edits since you quoted an old version of my post).
How should this be interpreted if multiple channels are driven? If the ratings are given "per channel", does that not mean it assumes all channels see the given load, respectively, at the same time?
The total load dropping below 2 ohms shouldn't matter if Yamaha has given ratings at 4 ohms nominal per channel ... But maybe the fact that the thing shut down with two sets of 6 ohm speakers is the smoking gun.
