Why is high mic placement often recommended?

Discussion in 'Live Sound' started by skygzr, May 5, 2007.

  1. skygzr

    skygzr Guest

    Hi All -

    I've read any number of times that a good place for live recording mics is up in the air; "the higher the better" was indicated on more than one occasion.

    What characterizes the difference in sound between typical ear-level and higher up? What makes it better?

    I understand that this is probably a generalization and isn't always true, but it seems to be recommended most of the time.

    This also implies that the best sound (at least from a recording standpoint) is not where the audience is sitting, at least in most rooms.
  2. Cucco

    Cucco Distinguished Member

    Mar 8, 2004
    Fredericksburg, VA
    Hey Sky!

    That advise is particularly applicable to large ensemble recording (specifically symphony orchestra, some chorus work, wind ensemble, etc.)

    It has more to do with line of sight than anything else. Sound is obscured, deflected or absorbed when not in the line of sight of the microphones.

    I would differ in opinion that "higher is better." I think "high enough is better." What I mean by that is, just because you have a 15' stand to put above an orchestra doesn't mean you should actually be 15' above the floor of the stage. In fact, my personal preferences always dictate that I just get the mic high enough that everyone in the orchestra can see it.

    This will insure that each musician's sound arrives at the microphone at the appropriate time.

    The problem with going *too* high is simple.....kinda.

    Think of a triangle. One point of the triangle is made at the point of the microphone, another at the front row of musicians and the final point at the last row of musicians. As you raise the microphone, the distance between it and the front row of musicians changes at about a 1:1 ratio - meaning if you raise the stand an additional foot, you increase the distance between those two points by about 1 foot.

    On the other hand, as you raise the mic stand, the distance (delta) between the mic stand and the last row of musicians is a smaller ratio (perhaps as low as even .15:1. In other words, you raise the stand a foot and the distance delta between the mic and the last row of musicians may actually only change by an inch or two.

    What this all means is - beyond a certain point, you collapse the depth of the ensemble the higher you fly the mics. If you want a VERY deep and accurate representation of the depth of the ensemble, you should reach a logical point in height where the delta between the mic and the two points in the orchestra is appropriate. Again, I often find this point to be "just high enough."

    All that being said, I also like to go just a little higher than that quite often and angle the microphones down a bit (maybe 15 degrees). Especially with mics that are clean off-axis, you will get a much "richer" sound this way.

    Does that make sense?

  3. Cucco

    Cucco Distinguished Member

    Mar 8, 2004
    Fredericksburg, VA
    To add to that, I guess I should also mention that, of course, distance of sound travelled equates to a later arrival time at the microphone which equates to a more distant sounding source.

    When listening to an orchestra, one is not expecting to hear the horns sitting in the violin section. So, the higher you raise the stand the smaller the delta between mic and front row and mic and back row becomes. This is where the collapse in image comes from. If the mic somehow wound up at a point in which it were equidistant from all instruments, it would sound like an entire orchestra eminating from one single point in space upon playback.


  4. skygzr

    skygzr Guest

    Thanks for the insight...that makes sense. I was also wondering if some frequencies preferentially get trapped near the floor.
  5. JoeH

    JoeH Distinguished Member

    Jun 22, 2004
    Philadelphia, PA/ Greenville, DE
    Home Page:
    I can tell you that (generally) the best place to mic a good solo violin is over the top of it, not out directly in front. (Instruments like the violin do not "Beam" sound out the way a horn does...)

    Somone once told me to think of the violin as akin to a fountain of sound; it comes UP and out of the instrument almost omnidirectional, but with more emphasis towards the front plane of the instrument - the one that faces the audience. Working with this in mind, it's easy to hear the difference almost immediately, once you begin mic'ing more above than in front of it, at least as a general rule.

    Also, sound tends to reflect up from most stone and hardwood floors, and you'll get a better blend a bit higher up than right in front of the ensemble.

    With a high vaulted ceiling, sound has a tendency to propagate up there and (in most cases) blend in an appealing fashion, as in large churches and big auditoriums with good acoustics.

    Not only that, for the kind of blend Jeremy and others are referring to, it's better to go UP more than it is to simply go OUT - not just into the middle of the audience, for example, where you have distance but not nec. blend - and certainly more audience noises like breathing, wheezing, coughing and general moving around in their seats.

    Hope that makes sense.

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