Topic: Mic Trees Affecting Sound?

[newplanet7]

Does anyone else wonder if/how much sound is affected with
a ton of mics on top of one another?
To me it seems like the pick-up pattern would change like baffling.
Here's a pic that got me thinking.
http://taperssection.com/index.php?topic=136702.0

[disco]

Does anyone else wonder if/how much sound is affected with
a ton of mics on top of one another?
To me it seems like the pick-up pattern would change like baffling.
Here's a pic that got me thinking.
http://taperssection.com/index.php?topic=136702.0

were you thinking that they needed to add a few more to that tree?
I can't imagine it doesn't make a difference, it'd be interesting to compare sources for that tree relative to something on a solo stand (if there was one)

[page]

Does it make a difference? Sure. Does it make a large difference? That's the real question to me. If using a hat makes a sonic difference, then I'd expect a hard mic between my cap and the stack would as well. Reflections less so in my mind, but we have a venue where the left wall tapers inward more and faster and that side seems to reflect bass better then the right side which is out in the open (or at least only one reflection point). I suspect the mics reflect sound, but I'm not sure it's the biggest factor.

I remember standing behind that sucker and wondering if my ears weren't playing tricks on me with the difference of the left (unobstructed) and right (obstructed) stacks and the >7khz range.

Ironically, tests at home could be done to get an idea, not necessarily conclusive, but an idea.

[stevetoney]

I'd bet that an A vs. B recording of same two rigs sitting side-by-side, one on a cluttered mic tree, the other by itself, would sound identical out in the audience of a Phish show.  Put the same mics in a studio where every element of the sound is perfectly controlled, perhaps then you might be able to hear some effects of nearby reflective surfaces.  I'm not saying this is how it is, I'm just saying that's how I'd bet it is.

[runonce]

Im VERY particular about having some space around my mics. I want them to be at least a foot from anything.

I think those mic tress are nuts!

How could it NOT affect the sound?

But you'll have plenty of dudes saying "nah...my pull from Alpine smokes brah!"

[Todd R]

Interesting, I was just thinking about this last night as I was trying to figure out how to get a bunch of mics clustered together so I can do a hypercard comp tonight (Gefell m210 vs JWilliams modded AKG 460/ck63 vs Charter Oak m900 hypers).

For loud, PA driven material, I'm guessing that a tree like the one pictured wouldn't have too great an effect on the sound.  I'd guess that potential reflections would be more of an issue than a shadowing effect, but given the decibel level at a show, I wouldn't think this would amount to much.  On the shadowing, it would be frequency dependent, but for small diaphragm mics with at least a bit of spacing, I'm guessing that wouldn't really have much if any of an effect on frequencies below 10k or 12k hz.

Spending a bit of time reading, understanding, and applying some of the sound information provided in the Jecklin disk literature should help provide some of the theoretical understanding of the issue at hand.

[page]

How could it NOT affect the sound?

But you'll have plenty of dudes saying "nah...my pull from Alpine smokes brah!"

Those arn't mutually exclusive statements.

I'd bet that an A vs. B recording of same two rigs sitting side-by-side, one on a cluttered mic tree, the other by itself, would sound identical out in the audience of a Phish show.  Put the same mics in a studio where every element of the sound is perfectly controlled, perhaps then you might be able to hear some effects of nearby reflective surfaces.  I'm not saying this is how it is, I'm just saying that's how I'd bet it is.

Likely. I think the most potential for audible differences comes in having stuff front to back and blocking. If everything is on the same plane and can easily see the stacks, I think (read; hoping) that the reflection aspect is negligable.

[Todd R]

Interesting, like I said, I expect it is all negligible, but thought reflections would have been more of an issue.

Jecklin disks are 12+ inches in diameter, with mics very close to the surface, and are constructed to be sound-absorbing.  Even then, with the disk directly in the sound path (seen from the mic on the opposite side), the disk has no effect on frequencies below 200hz, they just go right around the barricade as if it isn't there. 

So a sound with a wavelength of 65 inches just moves around a 12" sound absorbing barrier as if it wasn't there. With that in mind, consider then the case for a mic tree with a bunch of SD mics: mics that are only 0.75" in diameter, potentially blocking another mic farther back, and even then being probably at least 2 or 3" away from the mic that it is blocking.  What frequencies and what wavelengths then become a problem?  In such a case, I'm thinking that any sound with a wavelength of more than 1.5" (twice the length of the diameter of the blocking mic) won't have an issue -- meaning sounds with frequencies below 8kHz wouldn't be an issue.

[SmokinJoe]

It can be a problem, but it doesn't have to be, at least not noticibly.  Vertical stacking with a clear shot forward should be fine obviously (who cares if the ceiling and floor reflections are reduced).  Most of the mics in that tree have a clear shot.  That one stereo mic in the back is probably effected, and maybe the right channel of that one pair of actives on the Left... which is pointing at the back of shure and DPA windscreens.

Rather than refer to that tree, I will refer to the Stone Church where I have first hand experience.  For those who haven't been there, there is an overhead I-beam DFC/FOB about 6" wide.  There must be pictures here somewhere... Prime real estate is just in front of a wooden post about 12' from stage.  If there are 2 tapers, usually one guy clamps to the left side of the beam and one guy clamps to the right.  If they both run DIN, there are 2 mics almost touching in the middle.  If one is pointing right into the other from 2 inches away, it definitely tends to mess with the sound, you can hear unbalance in a tape.  So if it looks "obviously bad" then it is.  If you move one forward a few inches, or a foot, then they aren't quite as close, and the sound tends to go "around" the other mic just fine, or at least I can't hear it, and we've had some pretty crowded setups right there.  I mean... when was the last time Ted only ran 1 pair of mics?

[newplanet7]

Rather than refer to that tree, I will refer to the Stone Church where I have first hand experience.  For those who haven't been there, there is an overhead I-beam DFC/FOB about 6" wide.  There must be pictures here somewhere... Prime real estate is just in front of a wooden post about 12' from stage.  If there are 2 tapers, usually one guy clamps to the left side of the beam and one guy clamps to the right.  If they both run DIN, there are 2 mics almost touching in the middle.  If one is pointing right into the other from 2 inches away, it definitely tends to mess with the sound, you can hear unbalance in a tape.

I was also thinking about the Stone Church Packed taper house too joe.
I've seen it happen there a # of times.

  I mean... when was the last time Ted only ran 1 pair of mics?

This!

[page]

meaning sounds with frequencies below 8kHz wouldn't be an issue.

While completely anecdotal on my part, I agree with this.

  I mean... when was the last time Ted only ran 1 pair of mics?

This!

Come on!! Don't hate on your local authorized AKG dealer, he's gotta take pictures for his seasonal catalog somehow... 

[Dr.FOB]

Most of the mics in that tree have a clear shot.  That one stereo mic in the back is probably effected,

http://bt.etree.org/details.php?id=536292

Listen for yourself....

[jazzgtrl4]

Most of the mics in that tree have a clear shot.  That one stereo mic in the back is probably effected,

http://bt.etree.org/details.php?id=536292

Listen for yourself....

just grabbed this, sounds great too me..

[mterry]

Most of the mics in that tree have a clear shot.  That one stereo mic in the back is probably effected,

http://bt.etree.org/details.php?id=536292

Listen for yourself....

I was back of the tree for 7/2 and couldn't have been happier with my section tapes

http://bt.etree.org/details.php?id=536447

Really, I just don't see it making a difference. I know sonically along the lines somewhere it might. However, the guy who is running his mics inches in front of mine is running an entirely different rig, so of course it will sound different. I just don't  see how much can be lost, especially in a concert with high SPLs. 

[Shadow_7]

High SPLs help.  I would imagine that the closer the obstruction is to the mic element, the worse the effect.  When I record a standing audience type concert and there's a lot of people there, there's a noticeable difference on the audio when I raise the camcorder up over peoples heads.  Fortunately my mics have a good 3' clearance above heads on the audio rig.  From what I've read on boundary type mics which would involve the reflections in question, you get a bit of a comb filtering effect if the mic element isn't flush with the reflective surface.  Not that the result would be that audible, but if you look at the spectrogram it'll look less like a rolling hill and more like a saw blade.  And if you have a directional mic (or two) an obstruction, any obstruction, can be significant.  Less of an issue with vertically stacked mics since most of our (desired) audio sources are coming from a horizontal plane.  Well more horizontal than vertical in most cases.