02-06-11: Almarg
“Woodiness,” “body,” etc. are for example certainly important aspects of warmth, and their successful reproduction involves capturing the fine detail and harmonic balance of the instrument. That in turn can be expected to be compromised as distance increases. On the other hand, massed strings, to cite another example, can sound overly bright at close distances. As was noted above, high frequencies will be attenuated more rapidly as a function of increasing distance than low and mid frequencies.
This is a good point, Al, and it makes perfect sense of the idea that, in at least some cases, warmth increases as the distance of the listener to the live event increases. That would explain the correlation you observed between recordings with ambient cues and those with warmth. On the other hand, it also seems to suggest that, for smaller scale performances, warmth might DECREASE as the distance of the listener to the live event increases. So maybe there is reason to believe that a common characteristic of warm recordings is that the distance of the microphone to the live event is “proportional” to the scale of the event being recorded. That idea makes a lot of sense to me.
Also, reflected energy will be subject to frequency response contouring as a result of both the greater distance it travels before reaching the listener or the mic’s, and the acoustic properties of the reflecting surface. Finally, and perhaps most significantly, summation of reflected energy with directly captured sound will result in comb filtering effects.
The first of these points is more or less what I meant in the OP by item #5, which I called “room resonance,” but would probably more accurately be called simply “room acoustics.” Having said that, it never occurred to me that comb filtering might be a detriment to a system’s warmth. That strikes me as a plausible idea, since the destructive interference of comb filtering effects could conceivably result in a kind of "harmonic thinning,” which might very well be experienced as a lack of warmth. An insightful observation, Al.
Bryon