hoot
Junior Member
Posts: 68
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Post by hoot on Feb 14, 2023 14:23:03 GMT -6
Hi all, I came across an engineer using a triple-spaced set of mics to record a choir in a live room and couldn’t help but play devils advocate with myself. The left and right mics were at least 15 to 20 feet apart with the center mic dead center.
Was this not a recipe for phase disaster? A triple-mic setup like a decca-tree is supposed to essentially be a slightly-bigger ORTF capture with a center mic to ground the center image for balance’s sake? Short distance between mics for phase coherency. With the mics this far apart, the distance is enough to create enough time difference to actually hear a flam in worst case scenario?
Please correct me if I’m wrong or if I need to be more open minded!
Thanks!
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Post by notneeson on Feb 14, 2023 16:35:36 GMT -6
Hi all, I came across an engineer using a triple-spaced set of mics to record a choir in a live room and couldn’t help but play devils advocate with myself. The left and right mics were at least 15 to 20 feet apart with the center mic dead center. Was this not a recipe for phase disaster? A triple-mic setup like a decca-tree is supposed to essentially be a slightly-bigger ORTF capture with a center mic to ground the center image for balance’s sake? Short distance between mics for phase coherency. With the mics this far apart, the distance is enough to create enough time difference to actually hear a flam in worst case scenario? Please correct me if I’m wrong or if I need to be more open minded! Thanks! At 15’ I don’t think you can still call it a Decca tree. |
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Post by Blackdawg on Feb 14, 2023 16:49:00 GMT -6
you sure there wasn't a stereo pair in the center?
Very common to have an ORTF or NOS array in the center then flying wide with another pair for out riggers. Do this often with large ensembles like orchestras/choirs/wind bands. It adds a lovely width and also detail from the players that are on the outsides of the ensemble.
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Post by jampa on Feb 14, 2023 16:56:18 GMT -6
Seems like a spaced pair with a centre fill
15' = 4.5m
4.5 / 343m/s = 13ms
13 < 40ms ; so within Haas effect range, shouldn't flam
Soundstage must be getting up there in size
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Post by Pueblo Audio on Feb 15, 2023 14:41:43 GMT -6
What you describe is what some classical recordists call a “3-way”. Usually spaces omnis 8-12 feet apart. The arrival delays between the mics is not great enough to cause an obvious echo/flam. But the comb filtering resulting from the delays is desired because it can result in a pleasing Chorus effect. Usually a blended choral presentation is what one looks for with a large choir. Using a 3-way sacrifices Pin point localization in favor of a more blended, “choral” sonority. This is entirely different than a Decca Tree.
While this is a common thought, Decca Tree is not a larger version of ORTF. The tree’s Omni mics are too far apart to exhibit near-coincident behavior. in this case frequency-directional omnis, spaced in an triangle, experience comb filtering while pointed at the front stands of an orchestra. This can render a “symphonic” sonority.
The question of whether these techniques are beautiful or just a phase disaster is aesthetic and in the ear of the beholder.
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hoot
Junior Member
Posts: 68
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Post by hoot on Feb 16, 2023 14:36:11 GMT -6
the comb filtering resulting from the delays is desired because it can result in a pleasing Chorus effect. Usually a blended choral presentation is what one looks for with a large choir. Using a 3-way sacrifices Pin point localization in favor of a more blended, “choral” sonority. Ahhh this is why I posted! So you’re saying that if a wash is the goal, space them out. For localization, keep it tight? |
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Post by Pueblo Audio on Feb 16, 2023 15:24:48 GMT -6
the comb filtering resulting from the delays is desired because it can result in a pleasing Chorus effect. Usually a blended choral presentation is what one looks for with a large choir. Using a 3-way sacrifices Pin point localization in favor of a more blended, “choral” sonority. Ahhh this is why I posted! So you’re saying that if a wash is the goal, space them out. For localization, keep it tight? That is roughly the spectrum but ,Haha, “a wash” might be going a bit far. To me that would be zero to random localization. The above techniques I described, while not pin-point, still can offer an impressive sound stage with nice apparent depth of field if the engineer knows their stuff. Not random. The other benefit is the use of Omni’s which have full frequency response and point on-axis to the ensemble. In contrast, coincident/XY techniques has very accurate left/right localization, no comb filtering and is completely mono compatible. The compromises: need to use cardioid or blumlien patterns which have attenuated low end. Plus the capsules will be pointed off-axis from the ensemble. The apparent depth of field will generally be more shallow. |
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