Invert phases ?

[kara]

I have a question to our sound gurus... 

On another forum somebody asked how best to create a simulation of a live recording.
He got the standard answers, reverb,eq... but there was also another answer, which intrigued me.

The suggestion was to let the mix play trough a PA and rerecord it with mic's. Then mix the second recording with the first one.
Until here I could follow, but then the poster stated : Be sure, when you do this that you invert the phases of your recording when you mix it with the original recording...
And here he lost me.
Can someone explain what this is and why you should do it ?

k
 

[Marc JX8P]

Inverting the phase of a waveform is simply flipping it around its vertical axis in a program. Or - outside of the digital realm - simply by switching around the audio signal coming out of the mic.

I have heard people tend to do this with parallel recordings (say of two mics recording one snare drum) but in this case I don't think there's an issue; the original and the 'processed' signal should be different enough that there won't be any comb filter effects. Still, you might want to try both (normal and inverted).

[rharv]

There are plugins that alter the phase for you. Some free.
 A little searching may find many.
 I think 'phaseBug' is one.

[Laguna Rising]

Yes, I use phaseBug, it's very easy and free !
Probably there are many others..

Cheers