Phase Switching I think it's called, anyone care to explain?

[melodiousmonk]

I've been looking into recording a lot lately because my band is getting ready to record our second album by ourselves. I once read on this forum about puting one guitar panned hard right and another one panned hard left with the phase switched. Then recently I read somewhere else that if you have an up facing mic and a down facing mic the phase on one of them needs to be switched. I partially know what phase switching does but how do you do it? Just feel free to astound me with your know how.

 

[Farview]

I partially know what phase switching does but how do you do it? Just feel free to astound me with your know how.

I have a switch on my board, I just hit it.

The phase switch is actually a polarity switch. It just makes + into - and - into +. There isn't that much more to it than that. If you don't have a switch, you can wire a cable backwards or just invert the wave in your DAW.

 

[bennychico11]

like Farview says...there is a switch on a mixer that does it. In a DAW program they will also call it "invert" sometimes. The symbol for polarity reverse is usually drawn as the greek letter Phi.

I once read on this forum about puting one guitar panned hard right and another one panned hard left with the phase switched.

you're close on this one...but not quite. Read up on a technique called MS (or Mid-Side) mic'ing. I think this is what you were referring to.

and read this (heated) thread about phase and polarity

 

[mixsit]

... I once read on this forum about puting one guitar panned hard right and another one panned hard left with the phase switched.

It makes an initially interesting pseudo-stereo effect. Completely mono incompatible too.

Then recently I read somewhere else that if you have an up facing mic and a down facing mic the phase on one of them needs to be switched.

Probably not assuming the same sound entering each mic but from the side. Rotating a mic would not tend to effect phase or polarity (at least not within the first 90 degrees?). Front-to-back on an open cab' or top-to-bottom on a drum is another mater but that is because the sound is actually being presented inverted to one of the mics.
Cheers.

 

[RAMI]

Is polarity black or white? In other words, are 2 instruments either in phase or out of phase, period? Or can you have SOME phase cancellation?

 

[mixsit]

Is polarity black or white? In other words, are 2 instruments either in phase or out of phase, period? Or can you have SOME phase cancellation?

Polarity is pretty black and white. (inversion without changing time) But 'phase, or partially out of phase issues generally apply to a given source being delivered by two or more dissimilar time paths, right? Two different sound sources would on the other hand still combine with build-ups (and dips too presumably) at various points. But it would seem that that would be out side of what's normally called phase or phase combing.
Does that follow?
If you have a single pitch, you can shift in time and be partially out of phase, combine and have an attenuation. With mixed pitches, the same thing gives you varying degrees of phase and attenuation (or boost) at various frequencies...
This is very good exorcise.
Wayne

 

[bennychico11]

If you have a single pitch, you can shift in time and be partially out of phase, combine and have an attenuation. With mixed pitches, the same thing gives you varying degrees of phase and attenuation (or boost) at various frequencies...

one of the reasons I advocate shifting the actual track if you are having phasing problems and are using a DAW that lets you do so. Unless the two signals are exacly 180 degrees out of phase, flipping the polarity isn't going to correct the two signals 100%. And even then...the phase of the two signals still won't line up exactly. Plus, if you flip the polarity of the original signal...then you're getting the opposite of what is coming out of the instrument, so why not just correct the signals phase instead?

 

[peritus]

I used to use "phase switching" in an attempt to remove/soften vocals before trying to remix a song.

The idea is that the vocals are mostly mono and that phase switching then converting to mono cancels out any signals that were originally mono within the song.... It was a hit or miss at best...

Cheers

 

[fazil]

//Is polarity black or white? In other words, are 2 instruments either in phase or out of phase, period? Or can you have SOME phase cancellation?//

This is exactly the reason why they should not print "PHASE" on a mixers polrev button.

It becomes so confusing !

Phase and polarity are two completely different things.

Phase is a time based phenomenon, depending on the wave frequency.
Polarity is nothing but a switch changing the hot and cold signal

Polarity is black and white.
Phase shift is a shift of a certain frequency. This is expressed in degrees and has nothing to do with polarity.

This whole confusion thing exists only because a sine wave shifted 180° (1/2T) will give the same result as inverting its polarity. This is not the case for complex waveforms.
It's also not the case if you shift every frequency 180°.
If you do this every frequency will be 1/2T later which is not the same as reversing polarity.