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Old December 26th, 2004, 08:52 PM   #1
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recording an orchestra in stereo? three mic Deca tree?

hello- I've been appointed with the task of recording an orchestra and an ochapella group completely seperate from video... that is, the audio will be recorded prior to shooting and then added in later, so a soundtrack sortof. The sound quality needs to be as high as possible within a respectable budget(as it may go to CD as well) I'm sort of an audio idiot, but i've done some research and found the best way to accomplish this is to record the entire orchestra simultaneously with a "deca tree" Mic formation...which is two paired microphones spaced equally one quarter from the center of the soundstage, angled slightly to the outside, and a third mic on the centerline, pushed up a few feet to create a triangular like configuration, Thus eliminating the worry of a "sound hole" in the middle. From what i've heard, this configuration, although cumbersome and time consuming to set up, yields amazing results with a fantasticly realistic "stereo dimension".
Now my question is, how can I record three different Mics at one time, while keeping the stereo of the paired mics? Should I get a fancy-pants USB interface that has three XLR inputs,(if they even make those) and record it on garageband on my Powermac? Or should I buy or rent a mixer or something with a bunch of inputs? Or can I somehow adapt a DAT or minidisc recorder to record 3 tracks simultaneously? Do i need multiple recorders?
As far as mics go, i've got a good ole' sm57, used mainly for voiceovers, but as far as the stereo pair go I was looking at the AKG C1000, which is a rather inexpensive cartoid/hypercartoid which is available in a twin pack from B&H. I'm sure i could find two to rent somewhere also. Are these good choices?
Now, I've also read that the three mic formation is not absolutely necassary, and you can get away with just two matched Mics, spaced equally, and record simultaneously to get just about the same stereo qualitys. Would this be an easier way to go?
The orchestra is about 30 people, and we will be recording in a church with high ceilings. (this church has two acoustic dampening panels in the back which i bet will lower the reverb)
I think the whole idea of this setup is to get good stereo all in one shot, when recording musicians track by track is impractible(like when you've got thirty of them) My main concern is how to get all the mics recorded simultaneously, while keeping the stereo. I've only done simple track by track recording procedures on garageband...and one more question, Am I completely insane?

-thanks
-alex
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Old December 26th, 2004, 10:24 PM   #2
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Something to consider is your target audience/format... if it's DVD/TV, then most people's equipment will not be able to produce a stereo image (their TV either gives a mono signal because of their hookup, or their speakers are spaced too close together to be meaningful). If it'll be shown in film festivals then your audience will likely hear stereo sound.

The following websites have some good information on stereo microphone techniques:

DPA Microphone "University"
http://www.dpamicrophones.com/

Sound on Sound Magazine, Stereo Mic Techniques
http://www.soundonsound.com/sos/1997...f1f716e5688792

The advantage stereo micing gives you is that the audience perceives a "sound stage" where you can locate where the various instruments are. It might give your music bigger emotional impact that way (like movie theatre sound in a way). It depends on the playback equipment though.

2- Also consider issues other than stereo:

- background noise. Scout the location for AC and such. Consider the time of day you're recording as there may be people milling around inside or traffic noise outside.

- audience noise. (only an issue for live performances)

- noise from the performers (i.e. shuffling on stage) Listen carefully and take steps to reduce noise if this happens. I guess listen carefully basically. If there's a problem then fix it.

- echo/reverb- How much do you want? If the room has too much, then you need to place the mics closer and/or add sound absorption (that may be hard if the room is big).

- microphone sound quality. If you rent, you should be able to get some very good quality gear for not a lot of money. Mackie mixers with VLZ-Pro preamps and $600 microphones are like $20CDN/day where I live. You probably don't need special/better preamps.

- microphone placement (relates to other issues). Certain places in a room might sound better than others, so it'd be great if you gave yourself time to experiment... plus mic stands to allow you to get the mic in the right place.

- balance. Are the various parts of the orchestra the right volume compared to each other? You might actually be able to get the conductor to help you out and get the right balance among the instruments. You could try giving him/her a headphone feed. (I haven't tried this.)
An expensive way to get the right balance/mix would be to mic every instrument.

- Tone of the sound. This would be related to the microphone and preamp you're using and the post processing you do (i.e. EQ, compression.)

- Dynamics. If your target format/audience doesn't have good sound systems or they'll be listening with high background noise, then you'll need to apply compression. Otherwise they just won't hear everything. It's probably a good idea to record with no compression (nice to have gear with high S/N ratio, and low background noise at the location) and apply a little compression in post.

That's pretty much what I know about doing this kind of recording. My own recordings aren't very good (low/mid-end shotgun mics sound terrible indoors) so I guess take this with a grain of salt.
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Old December 27th, 2004, 11:21 AM   #3
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alrighty, thanks for the help...and good links too. I think i'm going to ask around my local technical audio population to really fine tune this operation.
-alex
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Old January 1st, 2005, 07:56 AM   #4
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Re: recording an orchestra in stereo? three mic Deca tree?

<<<-- Originally posted by Alex Milne : hello- I've been appointed with the task of recording an orchestra and an ochapella group completely seperate from video... that is, the audio will be recorded prior to shooting and then added in later, so a soundtrack sortof. The sound quality needs to be as high as possible within a respectable budget(as it may go to CD as well) I'm sort of an audio idiot, but i've done some research and found the best way to accomplish this is to record the entire orchestra simultaneously with a "deca tree" Mic formation...which is two paired microphones spaced equally one quarter from the center of the soundstage, angled slightly to the outside, and a third mic on the centerline, pushed up a few feet to create a triangular like configuration, Thus eliminating the worry of a "sound hole" in the middle. From what i've heard, this configuration, although cumbersome and time consuming to set up, yields amazing results with a fantasticly realistic "stereo dimension".
Now my question is, how can I record three different Mics at one time, while keeping the stereo of the paired mics?

+++It's acapella, and you can't. You need three separate tracks for a Decca Tree. A Decca Tree is also very room dependent. I wouldn't try it if I were you. I might if I were me and, well, I AM and I have.


Should I get a fancy-pants USB interface that has three XLR inputs,(if they even make those) and record it on garageband on my Powermac? Or should I buy or rent a mixer or something with a bunch of inputs? Or can I somehow adapt a DAT or minidisc recorder to record 3 tracks simultaneously? Do i need multiple recorders?

+++You need something that'll record three tracks for a Decca Tree.

As far as mics go, i've got a good ole' sm57, used mainly for voiceovers, but as far as the stereo pair go I was looking at the AKG C1000, which is a rather inexpensive cartoid/hypercartoid which is available in a twin pack from B&H. I'm sure i could find two to rent somewhere also. Are these good choices?

+++Decca Tree mics are usually three high grade omnis. I wouldn't use a C1000 for much more than a doorstop and it's not an omni.

Now, I've also read that the three mic formation is not absolutely necassary, and you can get away with just two matched Mics, spaced equally, and record simultaneously to get just about the same stereo qualitys. Would this be an easier way to go?

+++Yes. But if the group spreads out too far or is too deep, you won't get proper coverage with just two omnis.

The orchestra is about 30 people, and we will be recording in a church with high ceilings. (this church has two acoustic dampening panels in the back which i bet will lower the reverb)

+++You have to be able to "hear"the right spot in the room, stick the mics there and record. A tall order for someone who isn't an experienced audio geek.

I think the whole idea of this setup is to get good stereo all in one shot, when recording musicians track by track is impractible(like when you've got thirty of them) My main concern is how to get all the mics recorded simultaneously, while keeping the stereo. I've only done simple track by track recording procedures on garageband...and one more question, Am I completely insane?

+++Get help. ...without it you will impale yourself on the sharp shards of audio disaster. Few of us are completely sane. It's simply a matter of degree. :)

30 people set up how? 6x5, 3x10?

Will this be for a service, with people in the sanctuary, or just a recording by itself. The congreagtion makes noises and you usually can't put the mics where you want (flown from overhead) because they are visually distracting.

If you get lucky and the group is three deep, you could use three spaced omnis with a mixer and go right to stereo. The deeper the group, the more you need to go higher to keep the front row from predominating.

You're still not out of the woods though. You need to be able to place the mics close enough to get good direct sound and not too much reverb wash. The amount is tempo dependent. What works nicely on a slow tune will pretty much suck on a faster tune.

Did I mention that your idea of getting help is an excellent one?

Smiles,

Ty Ford

-thanks
-alex -->>>
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