Why stereo delay has Phase button? [SOLVED]

[dnine89]

Hi

 

Now I'm reading the Apple's Logic pro X Effects manual - Stereo Delay

 

and now I have a question.

 

Why Stereo Delay has the phase invert button??

 

because of Phase cancelation between Left or Right Feedback and Crossfeed sound??

 

But as far as I know, phase invertion makes more phase cancelation, isn't right??

 

I'm so confusing now.

 

Sorry for my English and Thank you for read this.

[Holger Lagerfeldt]

Why Stereo Delay has the phase invert button??

 

because of Phase cancelation between Left or Right Feedback and Crossfeed sound??

Yes.

 

But as far as I know, phase invertion makes more phase cancelation, isn't right??

The correct labelling of this button should be "polarity inversion" in my opinion. There's no shifting of the phase since it's a simple non-delayed polarity inversion. It's a common labelling issue and some try to justify it by pointing out that a 180 degree phase shift will lead to a similar (but not identical) cancellation effect or that two related signals where one is polarity inverted can be said to be "out of phase". However, a 180 degree phase shift is obtained by a shift in time and isn't the same as a polarity inversion, so I prefer the term polarity inversion when time is not involved.

 

There are two ways of looking at polarity inversion: absolute and relative.

 

Absolute polarity is the concept of the polarity of a recorded or generated signal maintaining its sound pressure direction throughout the whole recording, mixing, mastering and playback chain. It is a very real phenomenon, but it's only audible with asymmetrical sounds such as a saw wave, but not with a sine tone. Listening for absolute polarity requires that you have a verified playback system that doesn't invert the polarity (many headphones and some CD players have inverted polarity), which also means its notoriously tricky to adjust for.

 

Relative polarity is the concept of two or more sounds playing at the same time where inverting the polarity of one will affect the way they interact. Polarity inversion in this case can not be said to cause more or less cancellation without knowing exactly what the signals are or by listening to the result.

 

So if you hear something that seems to cancel out it makes sense to see if inverting the polarity will help.

[dnine89]

Oh, really Thanks for your reply.

Because i'm study alone and there's no manual written in my language, your reply is so meaningful.

 

So, in your opinion, the polarity inversion is more suitable labelling for that button,

and Polarity inversion and 180 degree inversion are different.

(I understand difference between them in my language but can't write with English hahahaha)

 

so I need to use that button when I feel phase cancelation with no worry about more cancelation, right?

 

 

Thank you!!!!

[David Nahmani]

The quick answer is, try turning that button on and off, and listen to determine which one sounds better. Let your ears be the judge. Turning that button on may result in less or more phase cancelation (depending on the signal and the delay time), but phase cancelation is not inherently bad, and you may like one result more than the other, independent of which one causes more phase cancelation than the other.

[dnine89]

Ooh that's so simple way of think, yes always my ear's judge is most important. I forgot it for moments.

 

Thank you too, David!!

[David Nahmani]

You're welcome!

[stardustmedia]

... and Polarity inversion and 180 degree inversion are different.

 

As far as I understand it, a polarity inversion is always and only 180 degree and does not inflict time. I think there is no inversion of e.g. 45 degree, or 59 degree. Not sure, but the term "180 degree" could be wrong in this scenario and it's just a vernacular use.

 

With phase shift (inflicting time) you can have all values from 0 to 360 degree.

 

As David wrote, depending on the situation, polarity inversion may sound better. If you are not sure about what you hear, you can solo the wet (delay) signal (maybe also test together with the dry signal). Put a phase correlation meter on the master buss, so you can see how much cancellation there is. If it goes too much to -1 (usually on the left side), you have too much phase cancellation. Double check it by setting the master buss to mono (use e.g. the gain plugin). Values close to -1 will result in lot of signal loss, but may sound very wide

[David Nahmani]

a polarity inversion is always and only 180 degree and does not inflict time.

180 degree indicates a phase shift (and therefore a time operation), not a polarity inversion. Unless you have a completely symmetrical signal (like a sine wave), the results are different: try a 180 phase shift and a polarity inversion on a sawtooth waveform for example:

 

[stardustmedia]

I understand the difference between inversion and phaseshift. So saying "180 degree" about a polarity inversion is wrong. I'd say it's a "wrong" vernacular expression then.