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In a certain line-up of a live recording in a classical concert hall, there is a 50 persons choir situated behind a symphony orchestra with quite a few trombones, timpanies and a percussion section. The choir is as wide as the orchestra itself.

I now want to add support microphones for the choir for two reasons: to improve the balance in the mix, and to improve the intelligibility of their part. I hope to get good results with the following prerequisites:

  1. I prefer not to spend more than 2 audio channels, and use 2 condensor mics.
  2. I wish to have least possible crosstalk from the brass section and the percussion.
  3. I like these mics rather to give me the sound of a choir than the sound of a few singers in particular.
  4. I want to have the choir balanced well, i.e. not only hearing the middle singers or one voice louder than another.

Now, my own thoughts:

  • Using omnis is not an option due to the heavy crosstalk, neither is using very remotely positioned microphones. (Not good for intelligibility, and also hard to deal with crosstalk)
  • Using a XY or ORTF is good against the cross talk, but any system that places the two mics close together only gives me the middle few singers.

Recommendations?

Pelle
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2 Answers2

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There are a couple general rules about recording orchestras. One is that at least 80% of the sound should come from the main array in front of the orchestra. Another is the you should never treat spot mics as independent elements, cross talk is a good thing. If you have an AB omni or ORTF cardioid setup in the front of the orchestra, it is perfectly acceptable to use a widely spaced pair of omnis in the rear to capture the choir. In fact, it is one of the most common methods. Wide cardioids like the schoeps mk21 or dpa 4015 are also popular for this. Space them wide enought to capture the entire choir and pan them appropriately in the sound field. I would really discourage using a second coincident technique like ORTF or XY.

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    I agree on everything you write, (I tried it with MK21s once, and the sound was reasonable - I think I just don't like the sound of Schoeps but that's a different story. Never tried the 4015s.) though I always end up with a signal that is not capable of fixing the balance with the hard brass and the percussion. Especially when these instruments are playing very loud while the choir sings, I want to cover up for the psychological effect of distinguishing when you see it by slightly altering the balance (without shattering the depth perspective). I need a relatively isolated signal for that... –  Dec 15 '10 at 19:33
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    Just for the sake of completeness, unlike XY, ORTF is a non-coincident system, since there is a spatial difference of 17cm between the mics in ORTF. You probably just meant "stereo pair" in general. –  Dec 15 '10 at 19:35
  • Thanks for the correction, I was going to add "or near-coincident" but forgot. If you have an over zealous brass and percussion problem then I guess you are stuck with a tighter pattern mic set. I have had succesful setups with only 2 spaced cardioids, but it usually requires quite a bit of height to capture the entire choir (and then you are back to the problem of capturing too much of the back orchestra). If you add a third you could probably get closer and avoid the brass bleed. –  Dec 15 '10 at 23:42
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There's no perfect solution to this one. As you mentioned omnis are out of the question so go with cardioids or figure-8s with the nulls pointed at the brass and percussion. You could also put up some reflectors behind the orchestra to help reduce the bleed.
Where to place the mics is just a matter of finding the best compromise - far enough from the orchestra to prevent bleed, and far enough from the choir to get a good blend.

BenV
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