Glad to share what I can.
"They project a wide, deep image where the soundstage is at the front of the room."
True.
"The instrument position; eg, a guitar, is constant while the listener moves in space."
If location is clearly located in the recording and location remains constant then yes. Most recordings should but not all.
"No additional sound comes from behind the listener, correct?"
In most rooms with most recordings, no. But room acoustics play a factor. If the room is very lively behind teh listening position it is more possible. I seldom hear anything from behind me in any of my rooms. I can only think of of brief moments on one or two music recordings when that has occured. The one that comes to mind is when Mel Torme hits and holds a note perfectly for a good 5-10 seconds in "the Classic Concert" on Concord CD. The perfect resonance of his voice sounds like you are surrounded. Quite startling and impressive actually, but not a common thing at all.
"In the case of an orchestra on stage, the presentation would be as realistic as my electronics will allow. I have a low noise floor, so would the imaging present a good separation of instruments?"
Again a function of recording and setup and room size and acoustics and listening position (listening perspective from where you are seated, much like at a live concert), but again that is what I would expect when things are going well. That is the case in my main setup where I am able to optimize everything. In my family room setup which is less optimized out of necessity, not as much but that is the case there with any speaker I use. So like most things, it depends.
"I understand Ohms are not the last word in detail, but I'm looking for a realistic and natural reproduction of the concert hall."
The detail is hard to fault when set up right, when you are getting that big well defined soundstage, but they are not bright or etched at all. They excel with good live recordings. The only thing I have heard better is larger mbls in a much larger tailored showroom. The same mbls at most shows are nothing special. So as is typically the case its all in the setup and getting things optimized accordingly.
"They project a wide, deep image where the soundstage is at the front of the room."
True.
"The instrument position; eg, a guitar, is constant while the listener moves in space."
If location is clearly located in the recording and location remains constant then yes. Most recordings should but not all.
"No additional sound comes from behind the listener, correct?"
In most rooms with most recordings, no. But room acoustics play a factor. If the room is very lively behind teh listening position it is more possible. I seldom hear anything from behind me in any of my rooms. I can only think of of brief moments on one or two music recordings when that has occured. The one that comes to mind is when Mel Torme hits and holds a note perfectly for a good 5-10 seconds in "the Classic Concert" on Concord CD. The perfect resonance of his voice sounds like you are surrounded. Quite startling and impressive actually, but not a common thing at all.
"In the case of an orchestra on stage, the presentation would be as realistic as my electronics will allow. I have a low noise floor, so would the imaging present a good separation of instruments?"
Again a function of recording and setup and room size and acoustics and listening position (listening perspective from where you are seated, much like at a live concert), but again that is what I would expect when things are going well. That is the case in my main setup where I am able to optimize everything. In my family room setup which is less optimized out of necessity, not as much but that is the case there with any speaker I use. So like most things, it depends.
"I understand Ohms are not the last word in detail, but I'm looking for a realistic and natural reproduction of the concert hall."
The detail is hard to fault when set up right, when you are getting that big well defined soundstage, but they are not bright or etched at all. They excel with good live recordings. The only thing I have heard better is larger mbls in a much larger tailored showroom. The same mbls at most shows are nothing special. So as is typically the case its all in the setup and getting things optimized accordingly.