Question on phase

[superkev07]

Okay, in one of my audio classes there's this real ****** bag that talks like he knows everything about everything audio. Funny how this same guy, this time last year, thought RADAR was lagging during a punch because the red highlighting on the track wasn't in the exact same spot as the punch. It took me about ten minutes of arguing to try to get him to understand that RADAR's screen is an aid; listen for it and see if the punch sounds wrong.

Anyway, I've been unable to shirk his existence, and he remains in my audio classes. There have been many occasions this semester where we'll hear something gone awry in a particular track (a singular track), and he'll jump in with, "Oh, there must be some phase issues there..."

Am I wrong in thinking that for there to be phase issues multiple tracks must be involved? He makes this comment nearly weekly, and it'd be great to actually KNOW that he doesn't know what he's talking about. Or perhaps I'm just an ass... that's a possibility too.

[tidalbomb]

Mutliple mics need to be involved...

This is a great spot for a "Stupidest thing I heard in Recording School" thread.

My favorite was overhearing an arguement between two similar people debating which operating system sounded better, Mac or Windows.

[Jules]

Seems like a total ass.. Drinking triple espressos before any classes you share with him, will help you. Rocking from side to side hunched over and reading loudly to yourself from the Pro Tools software manual with a maniacal look on your face might scare him off from sitting near you.

[ebeam]

Well, he does sound like an ass, but multiple mics/tracks don't need to be involved to have phase issues.... You can have phase issues with one mic and multiple sources of sound, i.e. 2 speakers on a guitar cabinet, direct sound and sound reflected off a surface, etc.

[max cooper]

Originally Posted by ebeam

Well, he does sound like an ass, but multiple mics/tracks don't need to be involved to have phase issues.... You can have phase issues with one mic and multiple sources of sound, i.e. 2 speakers on a guitar cabinet, direct sound and sound reflected off a surface, etc.

There's a bit about this near the end of this article:

http://www.ethanwiner.com/EQPhase.html

"Some people claim they can hear phase shift in equalizers because when they boost the treble they hear a "phasey" sound. So they wrongly assume what they hear is the damaging phase shift everyone talks about. In truth, what they are hearing is comb filtering that was already present, but subdued. When a microphone is near a room boundary like a wall or ceiling, or when placed near the open lid of a grand piano, the delay between the direct and reflected sound creates a comb filter acoustically in the air. When the treble is boosted by EQ the comb filtering becomes more apparent. But the EQ did not add the phasey sound, it merely brought it out."

Interesting stuff. Mainly, it's about how EQ's work.

[not_so_new]

Some of the points above are valid, could be the case.

Let me add to what ebeam said. You can have phase issues with one track micing multiple sources just as you can have phase issues with multiple tracks on a single source. One track can have phase issues if there are issues with the same signal getting to the mic at different times.

For instance (only an example you probably would not do this), lets say you have a singer close to a reflective wall, maybe a glass door or something. The talent has one mic on her so no phase issues right? One track, one mic, one sound source.

Wrong.

Yes one track, one mic but if the reflected signal from the glass door is loud enough you will in effect have two audio sources. Because it is the same "take" you can and probably will have phase issues with the track, the delayed sound will arrive at the mic later then the source sound causing phase cancellations on a single track.

Hope this helps.

[Ethan Winer]

Kev,

> Am I wrong in thinking that for there to be phase issues multiple tracks must be involved? <

You already got all the right answers, so I'll clarify just one point:

Phase shift by itself is a total non-issue. The only time phase matters is when audio is combined with a phase shifted version of itself. As in the examples of multiple microphones on one source, or reflections off a glass window. In those cases what is audible is comb filtering, which is a series of peaks and deep nulls in the frequency response. Phase shift by itself is totally benign.

--Ethan

[not_so_new]

Originally Posted by Ethan Winer

Kev,

> Am I wrong in thinking that for there to be phase issues multiple tracks must be involved? <

You already got all the right answers, so I'll clarify just one point:

Phase shift by itself is a total non-issue. The only time phase matters is when audio is combined with a phase shifted version of itself. As in the examples of multiple microphones on one source, or reflections off a glass window. In those cases what is audible is comb filtering, which is a series of peaks and deep nulls in the frequency response. Phase shift by itself is totally benign.

--Ethan

thumbsup

[Shotgun]

What bothers me most about this thread is, where is the class instructor to explain what is or is not caused by phase-related issues to you folks? What are they doing in these recording schools, setting you guys up with a ProTools rig and telling you which button is red? If you have to come here for the answer to that question you're getting ass****ed on your tuition.

~S

[superkev07]

Originally Posted by Shotgun

What bothers me most about this thread is, where is the class instructor to explain what is or is not caused by phase-related issues to you folks? What are they doing in these recording schools, setting you guys up with a ProTools rig and telling you which button is red? If you have to come here for the answer to that question you're getting ass****ed on your tuition.

~S

Well, I agree that I'm being bent over in tuition, but not for this reason specifically.

In class when this kid makes the comments about phase, the professor usually corrects him with what the actual problem is (never phase, obviously), but he doesn't specifically address the issue of phase not occurring on a single track with a single source. I suppose if the student continues making an ass out of himself, then it'll be addressed specifically one of these days, but for now, we all just sigh and move on.

[Fletcher]

Originally Posted by superkev07

Okay, in one of my audio classes there's this real ****** bag that talks like he knows everything about everything audio. Funny how this same guy, this time last year, thought RADAR was lagging during a punch because the red highlighting on the track wasn't in the exact same spot as the punch.

Turn off the monitor. You don't need it to record... hell you don't need it for anything. Sometimes it makes editing a bit easier, sometimes it's good for when you're learning the arrangement of a song [that way you can see when you need to turn on things like BK Vox and what tracks they're on]... but other than that... turn off the monitor.

As for the guy saying that it's "phase related" on a regular basis... counter with "nah, I don't think so... sounds more like a lack of current on demand"... which is probably just as real a statement as his "phase issue" thing and equally difficult to confirm.

Best of luck with him [baseball bat in the alley could very possibly work wonders to improve his attitude].

Can I say "peace" after that last thought?

[audioez]

Reminds me when I was working as a tech at a school in boston....Some guy "student" runs into the tech shop and says,
"It's MONO and out of Phase"

[jbuntz]

If you accidently run a single track through about 1654332 allpass filters, you might have a 4 second delay from one point of the spectrum to the other. Until then, good luck hearing an out of phase soloed track.

[Ethan Winer]

JB,

> If you accidently run a single track through about 1654332 allpass filters <

Yeah, good point. I found this (old) article by phase expert David Clark who did what you describe, and got his permission to post it on my personal site:

www.ethanwiner.com/phase.html

--Ethan