Thanks for the details. Do you take the ceiling height into account when deciding how high to place the microphones, or is it just a matter of how high the booms will reach?
And why are string instruments usually recorded from up high, anyway? Seems like the best position would be down at ear level, where people are accustomed to hearing it. Of course, I've never listened to an orchestra from 10' in the air, so maybe it sounds much better up there!
If i could rent a lifeguard chair and sit right behind the conductor, I certainly would. I bet it sounds incredible.
There are a couple reasons to mic high. Most practically, it allows for a better front to back ratio. If you mic low in the front, the physical projection of sound from the other musicians will be blocked. It may sound nicely blended in the audience (unless you are sitting in the front row seats which sounds awful), but from a microphone's less forgiving perspective, the front row will be very present and the back very distant.
The second reason is physics. High frequencies, due to refraction, will move up and out away from the musician's warm bodies to cooler air slightly higher up. Usually 9 feet up right behind the conductor is the orchestra's "sweet spot" for stereo miking. Of course that varies depending on the room and the setup. Too low sounds dull and muddy, too high sounds harsh and washy.
Since orchestras usually perform in rooms with high ceilings and hopefully very good acoustics, a high microphone setup usually works. For a smaller rooms or 8ft high ceiling studios, you for sure want to avoid getting too close to any flat surface.