Hi prototype3a,
When we talk about DVD-Audio and SACD and the mixing of bass, we have a different kettle of fish. In my limited experience with these commercially moribund formats, mixing practices seemed to vary.
Sometimes, they used full-range speakers for all the channels; the two "rears" were at diagonals to your seating location and you were supposed to sit in the center of the room. That was the arrangement for a Sony SACD demo I attended. I don't recall a subwoofer in that demo, and some SACD and DVD-Audio mixes do not have a subwoofer channel.
It was totally impractical for home setups and didn't work well in demos. If you shifted your seat the slightest bit away from the sweet spot, the imaging defaulted to the rears if you were closer to the rears than the front left and right or to one side or the other. It was for this and numerous other reasons that these formats failed to catch on.
You may not believe that deep bass below 80 Hz is non-directional but it's true. When I was just an amateur enthusiast, I thought deep bass was directional too, and had left and right stereo subwoofers. Then I did some experiments, met Dr. Floyd Toole and some other acoustical scientists, and came to learn that the "directional" qualities of deep bass sounds are provided by the midrange and upper bass--the "crack" of a mallet against a bass drum, for instance, is what tells your ears and brain the direction and location of the bass drum. The lingering very deep reverberations, around 30 Hz are totally non-directional. As they linger and bounce around a concert hall, you have no idea where they are coming from.
Regards,
Alan
