…the various ambience extraction modes(DPLII, Neo:6, Neural Surround, Logic 7, etc.)aren't really "DSP" modes(maybe you just used the term in a very broad sense).
Yes I was using DSP in the broadest sense. But thanks for clarifying for others who may read this.
I certainly wouldn't characterize it as "one size fits all", but I've never come across a 2-channel source that wasn't improved at least to a small degree. The amount of ambience mixed in varies and to a limited extent the Dimension setting in DPLII can be used to send more or less of it to the surrounds. Suddenly switching from surround to straight stereo demonstrates how the sound field suddenly collapses toward the front.
Sorry I didn’t mean it to sound like anyone was implying that it should always be used. As you point out Dolby PLII(x) extracts the ambience mixed in, which is probably why I like it for all ambient and concert recordings. However, I’ve noticed with many recordings especially female vocals (my preference) it often (not always) changes the voice seeming to smear it out some. The net effect for me is the little added ambience doesn’t outweigh the changes in the front soundstage for most studio recordings.
I did try out the experiment you suggested. I alternately disconnected the front speakers and the surrounds and listened for what the processing did. It flattened out the front speakers sound when they were loosing the ambient sounds especially where lots of ambience had been present. Listening to only the surrounds/rears sounded sort of like leaving the hall to use the bathroom but still hearing part of the music in the background, but less muffled.
Suddenly switching from surround to straight stereo demonstrates how the sound field suddenly collapses toward the front.
While I certainly notice this with many recordings. It’s less noticeable and even the oposite for me with others. The Bangles SACD version of “Going Down to Liverpool” is the most striking example I’ve found it sounds much more airy and enveloping in 2.0 than with DPLII(x) in my room. I never even really like that song until I heard it in 2.0 on my M80s now I love it.
When I first got my system I thought everything sounded better using DPLII until I started experimenting and realized I only liked some of the recordings better that way because of the higher SPL when running in 5.1. When I adjusted the SPL for the extra speakers I found many of the studio recording sounded better to me in 2.0. The experiment you suggested confirmed to me that the recordings with lots of ambience always sounded better in DPLII(x) while less ambient studio recordings often but not always sounded better in 2.0.
Please note I’m not some sort of 2.0 audio purist. I came into quality audio very late in the game so no legacy to cling to here and I think I’ve established my position on not being a slave to conventional wisdom on many occasions. So I’m pretty sure I’m not fooling myself into thinking 2.0 sounds better for some recordings. It will be interesting to see how the new more spacious room I’m moving into will effect all of this.
Thanks for the discussion.