x/y micing questions

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PATRIOT2006

New member
When using this technique for acoustic guitar, steel string and nylon, do you place the mics next to each other at the same height or one on top of the other?
If micing from a couple of feet away do you generally have the mics positioned level to the instrument or higher and aiming down toward the instrument?
 
Ideally, the capsules should be at a 90 degree angle, with one right above the other, so that when you look from above, they cross in the middle, like an "x." Naturally, with this configuration, one mic will be pointed more toward the soundhole (louder) and one more up the fretboard (quieter). I keep them about level with the fretboard, but experiment to find what sounds good on your guitar in your room. Another technique, which I've seen but not tried, is positioning the mics vertically (or perpendicular to the ground, rather than parallel), such that one is pointed upward and the other is down. This would eliminate the soundhole/fretboard volume difference.
 
scrubs said:
Ideally, the capsules should be at a 90 degree angle, with one right above the other, so that when you look from above, they cross in the middle, like an "x."
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Actually, they should cross so that the diaphragms are aligned in the same plane, one above the other; more like the ends of the mics cross, not the bodies. Your method would create some serious phasing problems at 4,000 Hz.
 
Harvey Gerst said:
Actually, they should cross so that the diaphragms are aligned in the same plane, one above the other; more like the ends of the mics cross, not the bodies. Your method would create some serious phasing problems at 4,000 Hz.
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So the ends of the mics should be in the same vertical plane if I understand correctly. That is what I tried last night but I was about 2&1/2
feet from the mics and they were directly in front of the guitar body. Maybe I should try close micing and cross at around the 12th fret and see what results I can get. I have a bass rolloff on the mics I can use if necessary.
I am trying to eliminate that midrange sound.
 
I guess I need diagrams... I've been micing with the capsules like this


/\

I think I saw it drawn like that by you harvey on a usenet post once. Maybe I read it wrong, as I do that often.


You guys are saying that they should actually cross?

Like

X


.... I guess that would explain why they call it X micing instead of /\ micing..
 
demensia said:
I guess I need diagrams... I've been micing with the capsules like this

/\

I think I saw it drawn like that by you harvey on a usenet post once. Maybe I read it wrong, as I do that often.

You guys are saying that they should actually cross?

Like

X

.... I guess that would explain why they call it X micing instead of /\ micing..
Click to expand...
No, you have it right; like this:

/\

is correct.

For perfect alignment, the center of the diaphragms should be on exactly the same plane. For most small diaphragm mics, that's about 1/4" back from the very front end of the mic.
 
Harvey Gerst said:
Actually, they should cross so that the diaphragms are aligned in the same plane, one above the other; more like the ends of the mics cross, not the bodies. Your method would create some serious phasing problems at 4,000 Hz.
Click to expand...

I think we're describing the same thing, but you did it better. I meant that just the tips, where the diaphragm is, would cross like an x. Like in this pic:
 

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    XY.jpg
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If the bodies cross, it becomes an A/B stereo image... another beast entirely.
But that's just symantics.
(/ = X/T, X or / = A/B, ie if the capsules are roughly in the same physical space, it's X/Y, if not, it's A/B)
The main point to remember is that you've trying to get the capsules in the same plane as the wavefront. This is to eliminate the phase issue.
You should pretty much always be "aiming" for the 12th fret on a guitar- it's halfway along the string, and hence where you're going to get the most vibration in the string. The wavefront plane is along the soundboard, so keept that in mind when micing.

To see an X/Y configuration, look for a picture of a Rode NT-4. That's pretty much what you're aiming for (the capsule alignment, not the mic itself).
Otherwise I think everyone else (esp Harvey) has covered waht I was going to say.
 
cpl_crud said:
You should pretty much always be "aiming" for the 12th fret on a guitar- it's halfway along the string, and hence where you're going to get the most vibration in the string.
Click to expand...
hmmm... neck/body joint a good starting point for positioning with a steel string acoustic? - yes. But it has to do with the sound of the whole guitar, not the string itself.

Tim
 
Take a look at the "microphone university" at this site-

www.dpamicrophones.com

The technique where the mic bodies cross in the middle is ORTF. The so-called X-Y technique is correctly called coincedent stereo mic'ing. The University will take you through the 3:1 rule, mid-side mic'ing, and the Jecklin disc, among others.-Richie
 
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