I have one and have ran it that way with two 4-ohm 12's.
What they don't want you to do is connect two 4-0hm speakers to the two Channel-A (or B) outputs. That would be a 2-ohm load.
You can run a single cord to channel A, and then there is a Line Out from Channel A to jumper to Channel B. This is basically Dual Mono.
This is nice if you are using different speaker brands/models/ohms because you can balance the individual speaker volumes.
Or if you convert to Stereo somewhere along the line you can go directly to Channel A and Channel B inputs.
I never ran it bridged to one 12, although there is supposed to be a way to run a single speaker at 160W.
It looks like using Channel A input alone, and one speaker to Channel A Output, gets you the 160W. http://www.genzbenz.com/img/manuals/tw/ ... Manual.pdf