Mike, I've also cited Alan's two articles on DPLII in the past when contentions of stereo being more "natural" were raised. Actually his
"Stereo's Intrinsic Flaw" article discusses the basis in a little more detail, especially the "Big Two-Channel Flaw" section. Sure, those "Jazz Club", "Beer Garden", "Sportin' House", etc. DSP modes add artificial reverb and may or may not be pleasing to a listener, but DPLII, Logic 7, etc. add nothing artificial and simply extract the natural ambience from the stereo channels and steer them to the side or back where they belong. It often isn't realized that the majority of sound at a live performance doesn't reach the listeners from the front as direct sound, but as reflected sounds from the walls. This
article illustrates in fig. 10.4.1 that the "critical distance" where the reflected sound exceeds the direct sound can be around 4 feet in a typical listening room and even in a large concert hall is only about 20 feet.
As Joe points out, the effectiveness of the ambience steering varies from disc to disc; this appears to depend on how much ambience was mixed into the stereo channels from the front microphones or ambience mikes further back in the hall(if used). An extremely close-up recording with less ambience may be relatively flat, although DPLII's dimension control, which increases the level of the surround channels, can partially compensate for this.
