From the manual:
"One 8 ohm and two 4 ohm jacks are provided for speaker interfacing. The Badlander is not very sensitive to speaker mismatches and will not be damaged by them, except that very low impedance loads will cause the power tubes to wear faster."
"You can always have a higher resistance ( 16 ohms, for example ) without damaging results, but too low of a resistance will likely cause problems."
"When running a higher resistance ( for example: 8 ohm output into 16 ohm cabinet ), a slightly different feel and response will be eminent. A slight mismatch can provide a darker smoother tone with a little less output and attack. This response is a result of the amplifier running a bit cooler. Sometimes when using more than one cabinet a mismatch will be the only option."
And then it provides wiring diagrams if you want to convert your speaker cabinet's total output ohms from 16 to 4 if they are all 16 ohm speakers.