why is it?

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larrye

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Why is it if you split a commercial cd track then reverse the phase on one channel (leave the pans straight up) the instruments aren't cancelled like the vocals?

The way I thought it worked was the only thing thst would NOT BE cancelled would be those sounds that were out of phase. If this is true how come there is so much sound still left after a phase reversal?

Thanks,
Larrye
 
Vox is up the middle, so a split creates a copy that an places equal parts in both L/R. Phase reverse cancels because the L and R are identical. At least for most vocals. Typically the instruments are panned away from the vox with some type of delay to minimize phasing between L and R channels. Since the L and R are not identical the phase reversal won't create a complete null like the vox will.


SoMm
 
OK,
So the instruments are a little out of phase?

If you pan only, with NO effects, would there be TOTAL cancellation? Assuming, for discussion, there is not a summing issue.

The reason I ask is when I mix I will put various short delays (3-12 ms) on some of the instruments of a mix to get them out of the way of the vocal and to spread the stereo field. I like the sound but I wondered if that is how other people do it.
Larrye
 
I usually record everything twice if its going to be panned anywhere but 12:00. I'd try using more delay...like 37ms or so, play with the delay around there and youll see that 12ms just isn't enough to fend off phase problems. If your using delay to get separation, removing it will result in some phase cancellation if you flip the phase... not entirely. I always hear something.



SoMm
 
It has nothing to do with phase. You are not, and can not, reverse "phase". What you are doing is inverting the polarity. Phase is an issue of time, polarity is an issue of electrical direction, positive or negative. When you invert the polarity, and switch to mono, anything which was electrically identical on both sides (most commonly vocals, snare drum, kick drum, and bass guitar) will cancel out. Anything which is different on both sides will be effected less, and if an instrument is only on one side, it will not be effected at all.

This thread has every a great deal of good information about phase and polarity. They are two different things which many people don't understand well.


Light

"Cowards can never be moral."
M.K. Gandhi
 
larrye said:
The reason I ask is when I mix I will put various short delays (3-12 ms) on some of the instruments of a mix to get them out of the way of the vocal and to spread the stereo field. I like the sound but I wondered if that is how other people do it.
Larrye

Do what SOMM says, and track it twice. Nothing screams "amateur recording" like doubling something and wide panning it with short delays. :D
 
Ok, now I understand I used the incorrect term as far as phase reversal is concerned. I guess I should have said I inverted the polarity.

I wish I had the expertise to play a lot of instruments, but I don't. I use midi for strings, piano and other instruments for tracks to go with vocals. These midi files may have a little reverb and or chorus. I then record them as audio in stereo, then add a short delay to one of the channels. I realize that may scream amateur. That is why I ask "how do they do that". I know some CD are made with synths and samples for strings, piano's and etc. SO:

Why do the centered instuments (kick,vocals, base) disappear, while the strings, piano, and other instruments remain, when polarity is reversed on one channel?

Thanks,
Larrye
 
Light said:
It has nothing to do with phase.

Actually, were talking both. (But its not my fault) Only because of audio gear labeling. Im used to it... :) My polarity switch is labeled.... Phase! And the CEP2 says...phase.... And wavelab says phase.... and my preamps.... well some of them say "pol rev" Whew!

I forgot about that thread on phase and polarity!

I vote for Lights link to be a sticky in the newbie section under deciphering common audio marketing misconceptions.



Here is a pdf I found a while ago...

http://www.live-audio.com/studyhall/polarity_and_phase.pdf


Light said:

They are two different things which many console manufacturers don't understand well.

Light

"Cowards can never be moral."
M.K. Gandhi

Light is right :)


Chessrock... I never put delays on panned double tracks....Thats like faking an orgasm! I need to have my delays free for the guitar solo extrodinaire :)


SoMm
 
larrye said:
Why do the centered instuments (kick,vocals, base) disappear, while the strings, piano, and other instruments remain, when polarity is reversed on one channel?

When you invert the polarity of one track then mix it with the other track you only lose stuff that originally was on BOTH tracks. If the piano, strings, etc are only on one track to begin with then there is nothing on that inverted track to cancel out the other track.

If a track was panned to 80%R and 20%L and you inverted the L track you would lose 20% of the overall volume (more or less). If you lowered the volume of the R track and raised the volume of the L track you would eventually completely cancel out the part.
 
Son of Mixerman said:
I vote for Lights link to be a sticky in the newbie section under deciphering common audio marketing misconceptions.

Light is right :)


Thank you, though many others contributed good information to that thread. I just believe that fundamentals are very important, so I like to help with info about it, particularly things which are as misunderstood as phase polarity.


Light

"Cowards can never be moral."
M.K. Gandhi
 
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