UPDATE: Coincident Mics - LDC or SDC?

Thanks for reading this post.
 
I'm hoping to get some opinions from folks that have recorded Orchestral esambels AND/OR Choirs using Coincident pair recording techniques.
 
Background:  My 5 yr old daughter attends a private school and I have been volunteering my time helping the band director.  The band director approached me about recording 250 children singing a special song as a gift for the schools principal.  This will be recorded in the band hall or possible in the gym.  This would NOT be a live recroding.  Strictly a studio type session.  I think I want to record in the band hall, it has a nice live sound and I think this would be a more appropiate recording venue than the gym.
 
Anyway, I've never recorded a choir or a band ensamble before.  I do not own any SDC mics.  I do have a pair of AKG C3000 LDC's .   The school has several Shure SM81 mics that might be more appropiate for this session. Both SM81's and C3000 are Cardioid mics. In addition, the schools symphonic bands will be performing in the next month and I have also offered to record this live event that will take place in the school's gym.
 
My question is: Recording the Choir and Bands - SM81 or C3000's?  If you recommend the C3000's how would you set them up?  Would you go with a Blumlein type setup with the mic's orientated in the verticle position or would you try a horizontal setup to try to acheive some sort of X-Y configuration?
 
Thanks for your input.
Rich

You can still do X/Y or ORTF.

Do you have any specific need to protect for mono?

The SM81s will make a nice pair.

I do about 4 recordings each year of Kindergarten through 3rd grade kids chorus concerts.  After the many years of playing around with mic configs in the hall--which is pretty live--I've come up with something that the director likes. 

The kids are arranged in an arc on risers on the stage. I use 6 mics, an X/Y front and center (although it's actually a decoded mid/side). Then an A/B in front, but with a cardioid pattern not omni. And then 2 omnis at the back of the stage on high stands pointing down over the left and right sides.  In the diagram below, imagine the omnis over the "d"s in the 2nd row.


                    Kids
               Kids       Kids   
           Kids                Kids
                A    X/Y    B


The director liked a much closer sound for the kids, so the mics are a lot closer than I'd have them for an adult chorus. I try to avoid as much room ambience as possible, but of course there's always some. And even my rear omnis are a bit too "roomy".  If you're actually recording in a gym, then there will probably be way too much ambience and you'll have to get close with the mics.

This works for me, and the chorus director really likes the sound. As always, YMMV.

Gents, Thanks for the responses.
 
I have only begun to research these techniques as of recent since I've had no reason to explore this before now.
 
@nprime:  I realize Blumlein is specifically for figure 8 hence I questioned how one would do an X-Y with LDC mics.  I was wondering how one would do an X-Y config with LDC's.  Could this be acheived orienting the mics in a verticle arrangement similar to the Blumlein configuration?
 
@Mike:  If I use the SM81 there is no reason I couldn't do either X-Y or ORTF.  I'm just not familiar with the SM81.  I know the SM81 historically is know to be an excellent mic.  I personally do not have a specific need to protect aganist mono but, my ignorance is showing here.  Is there something I should be careful of here?
 
BTW, thanks for the recommendation on the SM81's.  I value your opinion.  Also, in my research on stereo mic-ing I came across your "Homemade Stereo Bar" thread.  I opted to buy the Sabra-Som stereo Bar as a result of your thread.  How did your homemade bar work?  Are you satisfied with your AEA Ribbons?
 
@ohhey:  This is obviously a complex subject and it looks like the SM81's in an X-Y config is the way to go.  Thanks!
 
@tarsier:  Exteremly helpful info.  Thanks!  I just might try the extra mic's as  you suggested.  It certaingly won't hurt and I won't have to use the extra positions if they don't work out. 
 
How high up were the omni's?
 
Thanks again everyone.
Rich
 
 

for a choir of 250 people I would not use just 2 mics!  tarsier's answer is probably where I'd start looking.

the last time I mic'd a choir we only had 80 and we used 4 mics.  X/Y in front and 2 SDCs pointing at the choir using the 3X rule (the A/B in his diagram).

adding a pair of overheads probably would have really helped as well for the one I did.

Rich, I love my Ribbons. The bar works great.

I have a pair of SM81s that I have used on singing ensembles. I have a pair of Schoeps MK41s as well.

The SM81s are very nice mics. The Schoeps are a bit nicer.

Where ever you end up... take some time to walk around while the singers are rehearsing. Listen for a nice spot to place your mic.

The room will have an influence... you may not want to just think in terms of a floor plan.

The idea of getting a bit closer to seperate the direct form the room seems like good advice.

The last small choir I recorded was in a nice sounding wood paneled and thick carpeted assembly room.

I set up a XY pair of Schoeps MK41s, a ORTF pair of Nueman TLM103s, a Left Right A B pair of AKG414s, and a SM81 room mic. We used the XY Schoeps because it sounded just right all by itself.

Placement was all fairly close... about 8 feet back, because I had concerns with building noise. The room sounded fine but there was extra noise.

The recording did sound close up but the harmonies smoothed everything into a nice deluxe feel.

anyways, I think there are a few technicalities for you to take care but in the end we all hope the ensemble sound sgreat in the room... because that's the most important thing.

best,
mike

UPDATE
 
Greetings to all!
Well Today was the day I had the recording session at my daughters school.  This session involved having 300 children singing to a split track.  Whew!
 
Due to the complexity of getting all the students into one room and inturupting too many classes at once the recording was done in two sessions.
 
I ended up using (2) Shure SM81's in an X-Y config and (2) LDC Spot mics.  My biggest challenges were ambient noise an the mic's picking up the sound track as it played back to the students so they could sing along.
 
Anyway, I've posted two mixes.  One mix has the X-Y's panned Hard Left and Right.  The other mix has the X-Y's with a more narrow pan.  Spot mic's are mixed where they are hardly noticeable.  
 
I'd like some feedback about the sound of the children singing.  I've selected the mix that I will most likely give to the School.  I'm curious to know what you guys think?
 
Clik the link in my signature.  The song is You Shine identified as Narrow and Wide.
 
Thanks,
Rich

I'd like some feedback about the sound of the children singing.

Sounds good to me, and I preferred the wide recording. I might quibble about the overall level of the kids--they're the star, so turn 'em up. But I also wouldn't tweak the thing to death, so just leave it alone.

What sort of processing did you use on the kids? They don't sound shrill like kids usually do in real life.

I like the overall feel of the wide mix as well.

I think I may have made a field decision and searched out a voice or two to put a spot mic on so they could float in front of the crowd with clear annunciation.

Years ago I did sound for a TV doc about the Guiness World record for simultaneous children reading The Cat in The Hat... a whole school district in a foot ball stadium. Somehow it was tighter and the words were easier to discern.

Your kids were a lot younger... I hadn't anticipated that it would be that loose a performance.

Seems like a great job overall considering how many kids. Wow!!!

best,
mike