Is Bass Non-Directional In A Two-Channel Rig?

The basic anwser is yes, bass is non directional in an any channel rig, but at different frequencies for different people. Some people start loosing the ability to discern where bass comes from as high as 120hz, by the time you get to 80 hz, no one can tell where it comes from.

I've got one sub near side wall, plane is slightly behind me, and another next to one of my mains. Both crossed well below 80Hz they work very well and direction is unnoticable.

Try putting the sub in a corner...

"Try putting the sub in a corner..."

Only if you want to excite all the primary modes of the room.

Kal

You can hear where the bass originates even below 40 hz. Again the box/enclosure is a giant passive upward frequency generator. A 40 hz crossover point will not stop the box from being pressurized above that selected frequency. You will increase the sound stage image size by roughly thirty percent with the proper implementation of time aligned stereo subs. Ground the subs to the floor
Tom