More Things I Don't Understand: Phasing

[jeffgowins3]

So now that I'm upgrading my studio to record drums (see the infamous FirePod debate), I've been reading a lot of manuals on such things. I've been hearing a lot about phasing, whether they tell me to flip the phase on a certain mic, etc., and I'm lost. I know how to do it, it's quite simple, I just don't know what it does and why I need to do it. So, can anyone tell me what mic phasing is in stupid people terms?

Thanks, you guys are incredible.

-JG

[deshead]

It helps to remember a little from highschool physics, specifically constructive and destructive interference.

When you have more than one mic pointed at the same source, each mic will pic up the same sound wave. However, if the mics are at different distances from the source, the sound will arrive at diffferent times. Depending on the nature of the sound, this can lead to destructive interference when the signals are mixed. The sound wave at one mic cancels out parts of the sound wave at the other.

This is a decent explanation: http://www.recordingeq.com/EQ/req1001/mmi.htm

The phase-invert switch flips a sound wave upside down, which usually reduces the effect. A better technique though, if you're working on a computer, is to zoom in and nudge the recorded waves so that they line up.

[jute gyte]

Also on this subject, I've read in various audio technology books about stereo phasing problems being known to cause disorientation, nausea, etc., but I've never been able to cause this to occur. Any ideas?

[a bebop a rebop]

I don't know but I got sick to my stomach, like on the verge of throwing up, while I was driving around listening to Mt. Saint Michel Mix/St. Michaels Mount by Aphex Twin. That didn't have anything to do with phase-off-setting, I don't think. Towards the end of the piece everything starts to get shorter and tighter, so that sometimes it feels to me like a hammer pounding on my brain.

Yeah, so phasing...

[deshead]

Also on this subject, I've read in various audio technology books about stereo phasing problems being known to cause disorientation, nausea, etc., but I've never been able to cause this to occur. Any ideas?

Doppler phasing, in stereo

Combine with the Haas effect, and you'll have folks hurling in no time.

[jute gyte]

Is there a proper method to achieve this with software? I've been trying this:

• Take a mono file
  Convert it to stereo
  Invert one of the channels
  And delay one of the channels

but it's not really getting me results. I think I might not be understanding the articles fully.

[blue]

to do which? doppler? there are a bunch of doppler plugins out there. i dunno how you'd do it with wave manipulation, other than condensing and stretching the wave by hand - but you'd lose time coherency very quickly doing it by hand.

here are a bunch of VSTS..

http://www.google.com/search?client=fir ... gle+Search

[deshead]

Not sure how you'd do Doppler phasing in software. Some kind of subtle pitch shift effect, I suppose.

As for the Haas effect, I don't think you need to phase invert the dup'd channel. Just slap a delay on it. As long as the 2 channels are hard-panned, and the delay is less than 20ms or so, you'll hear the signal moved to one side.

[blue]

So now that I'm upgrading my studio to record drums (see the infamous FirePod debate), I've been reading a lot of manuals on such things. I've been hearing a lot about phasing, whether they tell me to flip the phase on a certain mic, etc., and I'm lost. I know how to do it, it's quite simple, I just don't know what it does and why I need to do it. So, can anyone tell me what mic phasing is in stupid people terms?

Thanks, you guys are incredible.

-JG

when two tracks of the same sound are out phase, the wave peaks will happen at different times. this leads to the sound being "weak" or "hollow." if the waves are in-phase but out of time, you'll hear a slight doubling or short echo. OOP is hard to hear in high frequencies, but leads to a general poor quality of sound. on bass frequencies, it can cancel the sound out entirely.

generally, phasing is only an issue if you are recording a source from two or more mics. for instance, if you have 5 mics on a drum set and all 5 are getting bleed from the bass drum, you could lose punch and thump if some are out of phase but audible.

like des said, the best way to fix that is to line up all of your drum tracks and zoom way in on them, until you can see the actual waveform. you want the peaks and valleys to happen at the same time, and be in the same direction (a bass drum hit should start with a positive peak on every track). if you ever get a chance to play around with multiple mics on a bass source, you can hear the difference of lining up the tracks and getting them in phase immediately. even a few ms can make a big difference in the "solidity" of the sound.

phase problems aren't just caused by reversed lines in the mics - they can also be caused by positioning. if one mic is slightly farther away from another, the source wave can hit the first mic on a peak and the second on a valley.

if you're letting your drum mics bleed, and esp if you're recording with only a few mics, it's a good idea to get them all equidistant from the loudest source, usually your snare. you can do this with a tape measure or piece of string or something.

i can post some screenshots if this still isn't making sense. cleaning up drum phase is usually my first chore after recording. once you get the hang of it you can do it really quickly, and man does it ever make a difference.

[jute gyte]

I'm using some effects now, but I'm not getting any results that are making me feel nauseous, unfortunately. Since when the problem occurs it is generally due to mismatched speaker connections, I would think that a simply inverting one of the channels would duplicate the effect. It makes things sound 'weak' and 'hollow' like Blue mentioned, but that's hardly nausea-inducing. This is a hard thing to Google.

[Hoblit]

a good way to get a headache though:

take a track that is completely done and seperate the left and right tracks from each other... place one between 12ms - 18ms or 22-26 ahead of the other one. Listen to track through headphones. This is maddening. It's listenable...you can hear the song and everything...but it really starts to mess with you after a while.

[blue]

im pretty sure you need massive SPLs to induce nausea.

[Spud]

<a href="http://www.songfight.org/music/a_thousa ... 3">this</a> might help, if you are trying to induce nausea.

[Dan-O from Five-O]

If that doesn't work.....try this instead.

[jeffgowins3]

So all-in-all, what's the advice? Do I flip all of my drum tracks except one (i.e. flip all that are getting bleed from snare except snare?)

Thanks,
-JG

[Dan-O from Five-O]

Like Blue said it depends on your drum mic setup. If you're using 2 overhead mics, focus on getting them an equal distance apart before you worry about phase. If you have a phase issue, that's probably the first place you should check. If that's not it, try bringing each individual drum track up in the mix with the overhead tracks playing to try to isolate which mic is giving you the problem and then try reversing that mic's phase on your pre-amp when you re-record the track.

If that doesn't work settle for making people nauseous.

[blue]

So all-in-all, what's the advice? Do I flip all of my drum tracks except one (i.e. flip all that are getting bleed from snare except snare?)

Thanks,
-JG

no, don't go flipping crap willy-nilly. just do your recording and see how it goes.