I made a search on the subject and the closest I got is this:
which talks about a receiver with an impedance switch.
How about receivers/amps that do not have this switch? Specifically, is there any risk to the speakers or amp in doing this for:
Both have two speakers outputs; thinking in connecting 4 ohm in one and 8 ohm in the other. Only one output would be used. (There is always a possibility though of mistakenly keeping both..)