I am a real beginner here and am gathering what info I can from folks who seem to know. One fellow, "Dr. Bob" at UConn, posted the following on getting a hall "right" for recording. It seems quite good and a good starting point for me and perhaps for you, too. I post this acknowledging its source is Dr. Bob and not me:
I only document when I know that I'll need to do the exact same thing again. When I go record large ensembles, my microphone setup is largely dictated by the repertoire that is to be played. I will likely mic differently for Richard Strauss than I will for Mozart or Bach. Since I find that the same group will play differently in the same room based on the repertoire, I will approach each job as an individual job choosing mics and placement for it.
Here is a quick sketch that shows my basic setup in the church I regularly record oratorios in. Slightly modified according to what exactly is to be played, but it usually starts off like this. A through G mics are flying.
A B are KM183 about 3ft spaced, height 12 ft, often with DIY eyeballs.
C D E usually Straus Packets, so far MBHO omnis (will be MK2s soon) and KM184.
F G choir spots MK21
H timpani spot Oktava 219
I J soloist spots to taste, have used MBHO omnis, TLM170, MKH800, and others.
Most times I also add a double bass spot, which then is whatever mic I just happen to have in my hands
This church usually doesn't need woodwind or brass spots, since they come through very well on A through E.
So there's another sketch, this time of an orchestra in a somewhat dry but clean congress hall seating about 1,000.
As most times, I went for a main mic plus FEW spots approach recording Mendelssohn 4 "Italian".
A B are KM183s again, about 12 ft high
C KM184 for some violin presence, about 9 ft over stage level
D (missing, over Celli) MK4 for some cello presence (9ft)
E F were MK21 pointing towards woodwinds and brass (9 ft)
G the secret timpani weapon Oktava 219
H double bass close spot for string noise - AT3035
Re: Straus packets
A cardioid and an omni "packed" together, resulting in a wide cardioid pattern when summed equally. I don't actually connect them the way Volker Straus did, but record omni and cardioid to separate tracks so I can balance them in the mix. It might even happen that I change the omni/cardioid ratio during the piece according to what instruments are most important or need to be featured a little.
Re: KM183 AB pair
I use this in two ways: either as a real main pair, around 50 to 60 cm spacing, quite close to orchestra. In this usage, it makes at least 90% of the sound, and the other mics are up to 20 dB lower to bring out a tad of this or that.
On other occasions, it's an additional AB setup for a tad more coherence when using M3 or Decca setups as main mics. Not quite a room pair though. It might, depending on the music, actually still have the highest level, but the main threesome will be nearly as high in the mix.
Always a system of all mics, though, and taking one out will usually kill the whole balance.
Flanking mics, often at about 1/3 and 2/3 of stage width, usually panned hard L/R. If I use them, they are part of my main setup. Typically found in a Decca Tree, but can be found in other setups too.
Re: Placing of musicians
Usually they set up the way they're used to, and I make, if at all, very little changes. It's my job to adapt to the orchestra, not the other way round.
I might suggest setups, though. In the end, it's their decision, and I see accomodating to whatever they make up as a challenge that keeps my mind and ears alive.