Mike bar for Decca tree

Discussion in 'Pro Audio' started by normanstrong, Sep 18, 2004.

  1. normanstrong

    normanstrong Guest

    Does anyone make an adapter to connect 3 mikes in the form of a Decca
    tree to a single mike stand? I imagine it would have to have some
    means of balancing the load.

    Thanks,

    Norm
     
    normanstrong, Sep 18, 2004
    #1
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  2. Eric K. Weber, Sep 18, 2004
    #2
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  3. normanstrong

    Scott Dorsey Guest

    As far as I know, the AEA one is the only commercial one out there. Most of
    the folks I know doing Decca tree work have homebrews, mostly made from
    one-inch iron pipe. It's not too difficult to make your own, and since the
    spacing is constant and only the angle varies, it's really just a matter of
    drilling and tapping.

    Starbird also used to make one. I bet Manley still has the old tooling and can
    turn one out, but it might be a good bit more expensive than the AEA.
    --scott
     
    Scott Dorsey, Sep 19, 2004
    #3
  4. normanstrong

    Peter B. Guest



    I think it could be build using the Bogen triple mic t-bar as a start.
    You would have to find some place that would sell you 25mm diameter
    tubing to get the proper width you want. The rest of the parts could
    probably be ordered from Bogen. It's sort of like playing with tinker
    toys.

    I'd have to search Bogen's expansive website to see if it could be
    done. If it can, the stand would be solid as a rock, highly adjustable
    and most likely under $200.

    Peter
     
    Peter B., Sep 19, 2004
    #4
  5. normanstrong

    Peter B. Guest

    There is enough hardware here to put together a decca tree (not
    including extra tubing):

    http://www.micsupply.com/standaccessories.htm

    Plus you will end up with a lot of parts that can be configured to do
    just about any type of mic setup. All the tubing is aluminum. The mic
    mounts are cast aluminum, machined where it needs to be. Good stuff.


    It's not exactly low profile... but neither is a decca tree.


    Peter
     
    Peter B., Sep 19, 2004
    #5
  6. normanstrong

    Mike Rivers Guest

    A Decca Tree is pretty big, a few feet between the microphones. I
    don't think I'd want to put that on any normal sort of stand. Maybe
    the Latch Lake Music one. But that's getting you well beyond the $200
    range.


    --
    I'm really Mike Rivers ()
    However, until the spam goes away or Hell freezes over,
    lots of IP addresses are blocked from this system. If
    you e-mail me and it bounces, use your secret decoder ring
    and reach me here: double-m-eleven-double-zero at yahoo
     
    Mike Rivers, Sep 19, 2004
    #6
  7. normanstrong

    Scott Dorsey Guest

    Manley has the original Starbird pattern and they are still making the stands.
    They are just just as solid as ever, but you don't even want to know what they
    cost these days.

    The Atlas stands used to come a near second, but the current Atlas stuff is
    just flimsy junk.
    --scott
     
    Scott Dorsey, Sep 20, 2004
    #7
  8. normanstrong

    normanstrong Guest

    Excellent! Since I'll be using very light weight small diaphragm
    mikes I should be able to get away with stand mounting. The mikes
    will actually be PZMs with the metal plates removed.

    Thanks a bunch,

    Norm Strong
     
    normanstrong, Sep 20, 2004
    #8
  9. normanstrong

    Scott Dorsey Guest

    Ummmm.... this sort of defeats the whole principle, doesn't it?
    --scott
     
    Scott Dorsey, Sep 20, 2004
    #9
  10. normanstrong

    hank alrich Guest

    Why? A PZM is not a pressure zone mic without the plate. Why not use
    some little omni instead? Why rip the plates off of a PZM just to make a
    small omni?
     
    hank alrich, Sep 22, 2004
    #10
  11. normanstrong

    Scott Dorsey Guest

    In fact, if it's a real Crown PZM, the top end response of the capsule is
    specifically rolled off to compensate for the high end rise when it's mounted
    on the plate, so it will make a pretty poor small omni by itself anyway.

    BUT, since a small omni won't work worth a damn in a Decca tree anyway, it
    is sort of academic.
    --scott
     
    Scott Dorsey, Sep 22, 2004
    #11
  12. normanstrong

    normanstrong Guest

    Now you have my attention. Why won't small omnis work in a Decca
    tree? I really need to know. Thanks,

    Norm Strong
     
    normanstrong, Sep 22, 2004
    #12
  13. normanstrong

    Bob Smith Guest

    Most mic stands in general seem to be junk. There are a few exceptions. I
    started using Avenger lighting stands and booms. Much better though a lot
    heavier. Big mics stay in position.

    bobs

    Bob Smith
    BS Studios
    http://www.bsstudios.com
    we organize chaos
     
    Bob Smith, Sep 22, 2004
    #13
  14. normanstrong

    Scott Dorsey Guest

    Because you won't get any amplitude differences between channels, just
    exaggerated phase differences. What makes a Decca tree work the way it
    does is the directionality at high frequencies that you get from the M-50.

    The original idea of the Decca tree was to use the beaminess of the M-50
    to your advantage, and it does so very well. But it does not work very
    well with mikes that have significantly different characteristics.
    --scott
     
    Scott Dorsey, Sep 22, 2004
    #14
  15. normanstrong

    Mike Rivers Guest

    The Decca Tree mic arrangement doesn't follow any particular rules but
    just happens to work because of the pattern characteristics of the
    Neumann M50 that makes three mics a few feet apart in a triangle a
    "Decca Tree." Anything else is just three mics a few feet apart with
    the associated phase problems. Nothing special.

    You may be able to rig something with partially absorbent baffles to
    approximiate the high frequency directivity of the M50. If it works
    for you, name it the Norm Tree. (or something)

    --
    I'm really Mike Rivers ()
    However, until the spam goes away or Hell freezes over,
    lots of IP addresses are blocked from this system. If
    you e-mail me and it bounces, use your secret decoder ring
    and reach me here: double-m-eleven-double-zero at yahoo
     
    Mike Rivers, Sep 22, 2004
    #15
  16. Because small omnis have truly omni polar patterns, even at high frequencies. The Decca Tree works by taking advantage of the HF beaminess of the sphere-mounted moni in an M50.

    Josephson and Schoeps both sell add-on spheres for use with small (but not fractured PZM small) omnis. Think 20-22mm diameter bodies.
     
    Kurt Albershardt, Sep 22, 2004
    #16
  17. normanstrong

    normanstrong Guest

    Interesting. Is it true that the M-50's were all facing forward? If
    so, I fail to see how the beaminess will work. Or are the mikes
    facing outwards? Perhaps I should read up a bit more on the subject.
    It was my understanding that the Decca tree depended strictly on time
    of arrival cues.

    Norm
     
    normanstrong, Sep 23, 2004
    #17
  18. When I set up a decca tree, I face the side mics slightly forward, but
    mostly outward. The front mic is positioned straight ahead. With standard
    omnis that lack the beaminess, you don't end up with the exaggerated timing
    differences between microphones. Low frequencies on the M50 are quite
    omni-directional, but as you go higher in frequency, you get more
    directionality.

    The higher frequency information is what will often give us the directional
    information in a stereo configuration. With a lack of directionality on a
    good set of omnis, all frequencies are going to all microphones and
    therefore you loose some of your imaging. If you are effectively cutting
    off certain parts of the sound from certain microphones, you'll end up with
    a much better image.

    I can't afford a set of M50's (or even M150's) so I've had good luck with
    the Schoeps MK21 capsule for decca tree work. I find that while it is an
    approximation of the pattern in an M50, they are one of the closer mics out
    there to the pattern I'd want.

    --Ben

    --
    Benjamin Maas
    Fifth Circle Audio
    Los Angeles, CA
    http://www.fifthcircle.com

    Please remove "Nospam" from address for replies
     
    Benjamin Maas, Sep 23, 2004
    #18
  19. normanstrong

    Scott Dorsey Guest

    They are toed-out, a varying amount depending on the room.
    If you depend only on time of arrival cues, you get great imaging below
    around 1KC or so, and no imaging above that range. Your brain can't sort
    out phase differences at high frequencies, so you need to preserve intensity
    differences as well as phase differences in order to get a complete soundstage.
    --scott
     
    Scott Dorsey, Sep 23, 2004
    #19
  20. normanstrong

    Scott Dorsey Guest

    I actually was surprised at how well the 1" B&K measurement mikes work. With
    a ball around them, they are beamy enough to be surprisingly effective. Have
    you ever tried any of the Gefell stuff? I have heard some of their large
    diaphragm omnis used in a Decca tree and it sounded very close to the classic
    Decca sound.
    --scott
     
    Scott Dorsey, Sep 23, 2004
    #20
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