..Maybe not the 3:1 rule specifically. But bad stereo definitely applies. It's all a compromise. Stereo pair on the 50 and All cow bell, with band backup. Stereo pair at the press box and all audience with some band. One 35's is not because they are ideal locations, it's because they have the least number / percentage of distractions. I've been performing in various marching bands for 20 years. I've only been recording since 2007. Some groups are large goal line to goal line. Some are small rarely exceeding the 40's. At the 35's and away from the sideline generally yields better results than on the sideline.
I think we agree more than disagree here. It's hard to record such a large, moving group with one pair of mics. If it were me, I'd probably put a coincident pair at the 50 and omnis out on either side, or maybe just space 4 or 5 omnis down the field in a line.
What you all apparently blew out of proportion was my comment about having a wider space when further from the source. I really don't see how you're disbelieving that.
No one is disputing that. Spacing the mics wider has the effect of narrowing the recording angle (called the SRA for
Stereo Recording Angle in Stereo Zoom language). That's not the angle between the microphones, but the angle describing a recording area as seen from the mic position. The Stereo Recording Angle describes the region of sound sources that will be more or less evenly distributed across the playback stage between two speakers (assuming the speakers are setup the standard 60 degrees apart from each other). Sources outside that angle still get recorded of course, but they are reproduced at the edges of the soundstage- they are reproduced from one speaker or the other.(*)
If I'm farther away from something, it fills less of my field of view than the same object will if I'm close to it. So it makes sense to space my microphones more as I get farther away IF I want a sort of zoom effect that will keep the same distribution of sounds between the speakers. But that isn't natural, it's a special effect.
17cm 3' from the source of course. But half a mile back 17cm is like MONO for all intents.
No it's still just as stereo. But you can space the mics more to try and force a closer perspective by narrowing the stereo recording angle, sort of similar to looking through binoculars. Doing that distorts what it looks like or sounds like to the person actually standing there, but that might make for a better recording. Recording and playback is all about illusion anyway.
Would your 3D camera(s) in space be 2.5" apart (pupil to pupil)? OR 2.5 miles apart because you're 50 miles or more from the subject?
This is parallax, and is exactly how older military optical rangfinders worked (around 4' apart) and also the focusing mechanism on older film camers (on a smaller scale of an inch or so). It is also how stereoscopic cameras work with a spacing close to the distance between human eyes. In that case the spacing can be pushed tigher or wider to exagerate or de-emphasize the 3-d effect and depth of field. 2.5 miles apart becomes applicable for things like radio telescopes pointed at the cosmos.
(*) because the time (and maybe level) differences become so large that you end up effectively with two mono recordings. Sort of what the 3:1 rule is trying to do, and another way of understanding how that rule dosen't apply to stereo recording, because it's entire aim is to NOT make a stereo recording, but two mono ones.