You Can... BUT It will damage your Amp (Head).
I did this by accident, I plugged an LMK Head to one 8 ohm speaker and one 4 ohm Speakers (which I thought was an 8 ohm).
It sounded ok, but I only did this for less then a minute, when I plugged the speakons off, I realize I made a mistake, luckily nothing happened.
So, if you do this by accident and not run it like that for only a short moment, like I did, it's ok, but if you do this on purpose, that's not wise at all
