Flipping phase...

[Snarl 12/8]

That big sucking sound you hear is your speaker cones moving away from you!

[vvv]

FWIW, it helps me to remember that phase shift requires 2 or more tracks with time-shifting against each other involved; polarity is adjusted by a 180 degree "flip" or "invert" (or some other degree of change), in place.

Eh, I think I got that right ...

[Nick Sevilla]

@ Nick

Question: If I have, let's say, a single vocal track. It's the only thing I have recorded. There is nothing to cancel, etc. If I flip the phase, will it change the sound of the individual track? I understand that phase flipping can affect the way a track cancels/interacts with other signals, but what about itself? Does phase flipping alter the tone of the thing that is flipped? If so, how exactly does this work?

it does matter.....

Question: If I have, let's say, a single vocal track. It's the only thing I have recorded. There is nothing to cancel, etc. If I flip the phase, will it change the sound of the individual track? I understand that phase flipping can affect the way a track cancels/interacts with other signals, but what about itself? Does phase flipping alter the tone of the thing that is flipped? If so, how exactly does this work?

No.

This really isn't a contradiction?

No. Waltz is talking about POLARITY, absolute phase of an electrical signal.
I am talking about phase, in relationship to a 360 degree circle. Most of the posts here talk, or reference this 360 degrees of phase.

Waltz is correct in that when dealing with ONE signal going through a playback system, absolute polarity is crucial, in order to play back the correct way.
If you go back and re-read his post, you can understand what he is talking about, and understand that he is referencing only the electrical absolute polarity of a signal, NOT a degree of phase shift.

This term, is very hard to fully understand until you study a little geometry, and a little basic electrical theory.

Maybe this will help you to "see" what we are talking about here:

Sound ALWAYS is propagated in 3 dimensions, plus a fourth... time. I will concern myself ONLY with the first three dimensions, for this explanation. THen I'll add time at the end.

Imagine a singular point, say a bell suspended in the middle of a room. When struck, the bell will vibrate, and the physical movement of the bell itself will disturb the air immediately around the bell itself. Since the bell is immersed completely in air, it will disturb this air all around it, in a shape immediately very similar to the shape of the bell, around the surface of the bell. Imagine the immediate initial vibration as a shape of the bell, completely surrounding the bell, and immediately propagating via molecular transfer to the surrounding air molecules, in a direction determined both by the shape of the bell, and the force with which the bell is vibrating. the speed will be the speed of sound, adjusted for the speed that the bell is vibrating at.

So, this initial disturbing of the air around the bell, can be thought of as having an initial outwards direction, or vector, which for our purposes we call POSITIVE. This energy goes outwards from the bell surface, and keeps going until it hits another air molecule, etc, until it runs out of energy. Subsequent vibrations, or disturbances, will follow the movement of the vibrating bell, accordingly. Imagine the direction of this vibration changing with time, into what we would call a NEGATIVE direction, as son as the bell's movement changes to an equal but opposite direction to the initial movement.

Got that so far?

Ok. Now, in order for a system in and adjacent room to the room we created, to capture those vibrations accurately, it HAS to replicate all the air disturbances EQUALLY throughout the system, and onto the final mechanical device, called a speaker, which HAS TO move IN EXACTLY THE SAME DIRECTION as the movements (vibrations) of the bell itself.

If you picture this, and could have two cameras looking at both the bell, and the speaker cone, you would see the bell vibrate in one direction, say, towards you, and the speaker HAS to do the same movement towards you, for you to perceive the sound accurately and correctly.

This movement accuracy, is the ABSOLUTE POLARITY of the BELL, and is duplicated by the transmission equipment onto the speaker cone.

Now. Digest this, and you get a lovely prize : Understanding.

Cheers

[Tim A]

We must always remember that some microphones for what ever reason aren't wired properly. so in order for the initial amplitude to be positive (assuming this is essential for NOTICEABLE accuracy), flipping the phase may be necessary.
Also you mentioned time being the fourth dimension in which sound travels. its equally important to talk about it, and in the grand scheme of say 5 cycles, verse the initial peak.....I bet it wouldn't be as noticeable. but then again...i dont know

[ashcat_lt]

There are about three people in the world who can actually hear the difference in absolute polarity of a sound signal and apparently a few more who think it matters.

Who's to say which way is correct to begin with? And how can be sure that you've captured it correctly without looking at it on a computer screen or maybe with those two cameras mentioned above? There are so many points in the signal path where this absolute polarity might be inverted that you'll drive yourself nuts sorting out your chain to get it to be "correct".

I for one have far more important things to do with my recording time, like making sure the shit I'm recording actually sounds good.

[Cathode_ray]

Seems this phenomena has more to impact(no pun intended) on transients - in or out would matter. I suspect a sine wave would be indifferent - it would care less. But something with large initial output(drum, plucked string) would be very effected.
But this raises the question; what "polarity" is the transient? Certainly a kick miced from the front will get positive signal. But what about from beater side? And which way does a plucked string(electric not acoustic) go... Hmmmm
Oh yeah and what if you push the bow instead of pull on a violin?

[highway51]

I flip the polarity/phase button on my preamps when tracking vocals all the time, usually not on anything else. My experience has been that the polarity switch seems to brighten the vocals and lessen the "boom" and the vocals tend to stick out in the mix better,maybe my preamp is broken cause it doesn't matter which mic I am using.

My experience tends to be supported by the fact that most ribbon mics are darker/bassier when you sing into the front while they are generally brighter when you sing or play guitar into the back.

My recording instructor at my university used to always hit the phase switch on preamps when tracking vocals to see which way it sounded better.

[kingtoad]

I flip the polarity/phase button on my preamps when tracking vocals all the time, usually not on anything else. My experience has been that the polarity switch seems to brighten the vocals and lessen the "boom" and the vocals tend to stick out in the mix better,maybe my preamp is broken cause it doesn't matter which mic I am using.

My experience tends to be supported by the fact that most ribbon mics are darker/bassier when you sing into the front while they are generally brighter when you sing or play guitar into the back.

My recording instructor at my university used to always hit the phase switch on preamps when tracking vocals to see which way it sounded better.

If you are getting a lot of headphone bleed then flipping the polarity could certainly make things less or more muddy in terms of the mics interaction with that bleed.

[jhamburg]

the "phase" button on a console or a mic pre is really a polarity switch.

for a sine wave switching the polarity is functionally equivalent to rotating the phase of the wave 180 deg.

any audible difference would be due to the fact that you might be in a node at your listening position where you weren't before. Just need to slide forward that half wavelength to get bac

joel

[donny]

i would bet that most of your favorite records are a complete mess in terms of absolute polarity. there is no wrong or right; some people like to make sure the polarity is CONSISTENT but even that is not neccesarily artistically "better".

[dfuruta]

the "phase" button on a console or a mic pre is really a polarity switch.

for a sine wave switching the polarity is functionally equivalent to rotating the phase of the wave 180 deg.

any audible difference would be due to the fact that you might be in a node at your listening position where you weren't before. Just need to slide forward that half wavelength to get bac

joel

Flipping the polarity shouldn't affect room modes?assuming the room is closed, there's always an anti-node at the wall and the spacing of the nodes in the room is just determined by the frequency of the standing wave.

[germaniac]

I once posted on a newsgroup a similar question about "phase" and got a verbal drubbing the likes of which I will never forget: the proper terminology for the topic at hand is POLARITY. The term "phase" as applied in the OP's question is a popular misnomer, and should be systematically corrected by anyone serious about recording. At least that's what all the angry engineers screamed while beating me.

After my wounds healed, I came away with the following:

--The term "phase" applies to a signal or parts of a signal with incremental degrees of shift in time/frequency relative to a given reference point. (e.g., "Something's making those cymbals sound "phasey" in the overhead mics.")

--The term "polarity" applies to the absolute 180-degree inversion/non-inversion of the entire signal. (e.g., "Invert (or reverse) the polarity of one of the overhead mics to hear if it corrects the problem with the cymbals.")

FWIW, I can only hear inverted polarity on an isolated track when I'm actually speaking into a mic, because the ear/head resonances change. Otherwise, sounds the same to me.


Joe

[highway51]

The headphone bleed makes alot of sense thanks, turning on the polarity always helps my vocal takes guess its the headphones.

[ricey]

this is as good a place as any to ask - i'm not the only one here that will want to know... the name of those polarity-testing boxes i saw once in a studio. one box plays a pulse through a little speaker, this gets held in front of the mic. the other box is held in front of the speaker, has a little mic and blinks red or green depending on the polarity of the chain. the engineer went around to each mic in the room... sound familiar to anyone?

[Andy Peters]

this is as good a place as any to ask - i'm not the only one here that will want to know... the name of those polarity-testing boxes i saw once in a studio. one box plays a pulse through a little speaker, this gets held in front of the mic. the other box is held in front of the speaker, has a little mic and blinks red or green depending on the polarity of the chain. the engineer went around to each mic in the room... sound familiar to anyone?

Galaxy Cricket.