Is it normal for the 2 overhead tracks to not be 100% lined up?

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RAMI

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I measure the distance of my overheads from my snare meticulously. They sound in phase, and they are, so this is more of a visual question.

I noticed when I magnified the view on them to maximum, they're ever so slightly not lined up. I'm talking maybe a frame or 2 at the most, don't know for sure.

Visually, should they be 100% lined up, or is this theoretically impossible?
 
RAMI said:
Visually, should they be 100% lined up, or is this theoretically impossible?
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It's impossible, unless all the drums are in a straight line.
In a normal setup, everything can't always be equidistant from both mics.

The convention (often) seems to be to keep snare and kick equidistant from each over head, in a standard overhead arrangement.
The floor tom will still reach one OH before the other though, for example.

If you record a snare only, do the two waveforms line up? I guess they should.

EDIT: Did I just try to tell RAMI about drums?
Bed time for Steen.......
 
Steenamaroo said:
If you record a snare only, do the two waveforms line up? I guess they should.
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Yeah, I guess i should have explained better. I line my mics up to be equal distance from the snare (I don' bother with the kik). But even the snare hits that are in the 2 overheads aren't 100% lined up. I mean, I have to maximize the view to see that they're slightly off.
 
It's 2am so the maths might hit the shit here....but

48k sample rate is 48 thousand audio samples per second, right? (Assuming that's what you work at)
And sound travels at 340m/s give or take.
So you'd need a discrepancy of 7mm to be out by one full sample, I think.

If I did that right, then it's certainly possible that the measurements are just out a little bit.
 
Steenamaroo said:
48k sample rate is 48 thousand audio samples per second, right? (Assuming that's what you work at)
And sound travels at 340m/s give or take.
So you'd need a discrepancy of 7mm to be out by one full sample, I think.
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OK, I'm sorry I asked. :laughings:
 
Thanks Steen. I was thinking the same thing but couldn't figure out the math. It's kinda like shooting...a 1/4" difference at 100m will miss the target at 500m.
 
When I mike up a kit, I most often use four mikes: kick, snare and overheads x 2. In Reaper, I assign kick and snare to separate tracks, but the overheads get recorded to a single stereo track. As a result, I've never had cause to examine whether they are lined up or not, and have never noticed any issues.
 
gecko zzed said:
When I mike up a kit, I most often use four mikes: kick, snare and overheads x 2. In Reaper, I assign kick and snare to separate tracks, but the overheads get recorded to a single stereo track. As a result, I've never had cause to examine whether they are lined up or not, and have never noticed any issues.
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Interesting. I do exaclty the same as you, except that I assign each overhead to a mono track, and then put those 2 tracks in a stereo folder.

EDIT: I just realized that there's really no reason to do it the way I do. I never thought of calling up a stereo track and not bothering with putting 2 mono tracks in a stereo folder. It's not as if I ever do something to one overhead that I don't do to the other. Thanx Geck, you just saved me a step and some space.
 
Don't forget that, with a stereo track (or two mono tracks used as stereo) it's the slight differences between the two channels that provide the directional information for the stereo image. If everything was perfectly lined up, you'd pretty much have a mono track.
 
Bobbsy said:
Don't forget that, with a stereo track (or two mono tracks used as stereo) it's the slight differences between the two channels that provide the directional information for the stereo image. If everything was perfectly lined up, you'd pretty much have a mono track.
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That's a good point, but I thought the reason the snare ends up in the middle of the stereo image is because it's hitting both mics at the same time. The "stereo" applies more to the rest of the kit, no? But, like I said, you may have a point.
 
Yup--if the snare is equidistant it'll appear in the middle of the stereo field. However, where are you measuring to on the snare? The matched distance can only apply to one precise point on the snare and, as somebody worked out earlier, millimetres of difference in the distance from a hit can mean one sample's difference. In even the size of a snare there's room for noticeable (but slight) differences.

Sound is a dynamic thing and the instruments that make the sounds have 3 dimensional sizes. A phase measurement is always frequency and distance dependent--you can never eliminate every single difference but, if you could I imagine your music would sound flat and artificial. The trick isn't to eliminate phase differences; it's just to be aware of the potential problems and make sure you get useful spatial information rather than ugly comb filtering peaks and cancellations.
 
Bobbsy said:
Yup--if the snare is equidistant it'll appear in the middle of the stereo field. However, where are you measuring to on the snare? The matched distance can only apply to one precise point on the snare and, as somebody worked out earlier, millimetres of difference in the distance from a hit can mean one sample's difference. In even the size of a snare there's room for noticeable (but slight) differences..
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Yup, antoher good point, Bob. :cool:

On a 14" snare, there's probably a 6"-8" diameter of play where it gets hit.
 
With a spaced pair of overheads there will always be things that don't line up. If you correct for one source you will throw other sources further out of phase. There is no "correct" alignment, just various compromises. I wouldn't even try to align drums with spaced overheads.

Using a coincident pair of overheads can somewhat solve this as you can align all the other sources to this reference, but even then bleed in other mics can never truly be all in alignment.
 
bouldersoundguy said:
With a spaced pair of overheads there will always be things that don't line up. If you correct for one source you will throw other sources further out of phase. There is no "correct" alignment, just various compromises. I wouldn't even try to align drums with spaced overheads.
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Absolutely. But that's why I mentioned that I'm measuring the distance from the overheads to the snare, so I was wondering if it was normal that even the snare hits are not 100% lined up when I zoom in all the way.

Bobbsy pretty much answered it when pointing out you'd have to hit the snare at exactly the precise point it was measured from every time, which is impossible.
 
...I think Steen answered it, too. But I couldn't understand a word he was saying. :eek:

:D
 
RAMI said:
...I think Steen answered it, too. But I couldn't understand a word he was saying. :eek:

:D
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Jesus....I thought you were kidding. lol.

FWIW, I did answer it.

Dummed down translation:
If you centre the snare to the overheads then hit the left side of the snare near the rim, the sound will reach your left mic a few samples before the right one.

Further dummed down translation:
An inch makes all the difference.
 
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RAMI said:
Absolutely. But that's why I mentioned that I'm measuring the distance from the overheads to the snare, so I was wondering if it was normal that even the snare hits are not 100% lined up when I zoom in all the way.

Bobbsy pretty much answered it when pointing out you'd have to hit the snare at exactly the precise point it was measured from every time, which is impossible.
Click to expand...

Since you're picking the snare up from different directions the waveforms will be different to some degree. The phase of different frequencies will vary with angle from the source so you can never truly align the two spaced overheads just with distance, even if the drummer hits the exact same spot every time. And, as has been pointed out, where exactly do you measure from on the snare? Everything else being equal a 6" variance starts comb filtering at about 1kHz. Do you measure from the center of the head, where the stick hits or the nearest edge of the snare? There's easily more than 6" variation among those spots and none of them is more correct than the others. Time and phase inevitably blur a little.

Just like time alignment in the DAW, using distance to correct one thing will make another less correct. But that's okay because some differences can be useful for creating a stereo image.
 
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