Why would you invert the polarity on an audio track?
- Thread starter calmAss
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bandcoach
Zukatoku - Mod Scientist
Phase inversion (what I think you mean by polarity) is a simple solution to a common audio problem. Sometimes the signal on a particular track is out of phase with the rest of the music, leading it to sound thin and without body or presence. So, it becomes important to flip the phase of the signal 180 degrees. This may not resolve all of the issues but will probably go a long way towards solving the problems created.
Of course the phase inversion may only lead to a conclusion that that the phase of the signal is not the problem - but at least it should form part of the troubleshooting on inter-modulation distortion issues with multiple audio tracks.
Of course the phase inversion may only lead to a conclusion that that the phase of the signal is not the problem - but at least it should form part of the troubleshooting on inter-modulation distortion issues with multiple audio tracks.
chris carter
New member
First, please don't confuse POLARITY with PHASE. The (mislabeled for goofy reasons) "phase" button is really a polarity reverse button. It's flips the polarity.
Among other reasons, the two most common reasons to use this button are:
1) When working with live signals with multiple mics, if things aren't mic'd well, you can get phase problems. Sometimes the phase is convenientaly close to the point where one signal is a half cycle away from it's related signal, in which case hitting the "phase" button (which is really a polarity reverse button!) will get you closer to a good sound. This is mainly only an issue with very complicated micing schemes like live drums.
2) Some sounds will sound different, plain and simple. There are two categories: transient and tone. Transient things like kicks are a big issue and you want the initial transient to push the speaker forward as opposed to backwards. It makes a subtle difference. With tone, things can go horribly wrong. Certain vowel sounds and many brass instruments have more of a sawtooth wave shape and flipping the polarity will drastically affect the tone. If the track was recorded with polarity reversed (miswired cable, for example, or the wrong side of a figure 8), then you can correct it with the magic button.
And of course, in hip-hop when you have things like layered kicks if they have opposite polarity it will sound more squishy than punchy. Common problem. I catch this kind of crap all the time when I mix records.
Among other reasons, the two most common reasons to use this button are:
1) When working with live signals with multiple mics, if things aren't mic'd well, you can get phase problems. Sometimes the phase is convenientaly close to the point where one signal is a half cycle away from it's related signal, in which case hitting the "phase" button (which is really a polarity reverse button!) will get you closer to a good sound. This is mainly only an issue with very complicated micing schemes like live drums.
2) Some sounds will sound different, plain and simple. There are two categories: transient and tone. Transient things like kicks are a big issue and you want the initial transient to push the speaker forward as opposed to backwards. It makes a subtle difference. With tone, things can go horribly wrong. Certain vowel sounds and many brass instruments have more of a sawtooth wave shape and flipping the polarity will drastically affect the tone. If the track was recorded with polarity reversed (miswired cable, for example, or the wrong side of a figure 8), then you can correct it with the magic button.
And of course, in hip-hop when you have things like layered kicks if they have opposite polarity it will sound more squishy than punchy. Common problem. I catch this kind of crap all the time when I mix records.
SafeandSound
Mastering Engineer
If you mic a snare drum with 2 mics one on top and one under (to pick up the snare springs underneath for more sizzle) You would probably want to phase invert the mic on the bottom so they are "in phase". (in any event you would listen and determine what is right)
This is one example, phase in recording and music in general is very important to understand.
It is also very useful for test purposes, null testing etc.
cheers
This is one example, phase in recording and music in general is very important to understand.
It is also very useful for test purposes, null testing etc.
cheers
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SafeandSound
Mastering Engineer
Yes but not phase inversion which is something entirely different.
In a mix you would use it only to correct a problem of a signal being "out of phase"
In a mix you would use it only to correct a problem of a signal being "out of phase"
Departure
New member
To solve phase issues (often used when mic'ing top and bottom of a drum in live applications) to create a phase effect (note that this track may dissapear in mono if you flip phase) or, if the track was recorded with the phase inverted, to revert it so that the initial punch of the sound is positive rather than negative.
Positive side of a waveform (the top side) is the amount the speaker moves away from the driver (compression), while the bottom side is the distance the speaker pulls back to complete the cycle (rarefaction). Reversing these doesn't necessarily effect the quality of a sound, but if there's a large initial punch, you can usually tell if that first smack is compression or rarefaction. This is typically only done on low-frequency percussive sounds. High frequencies complete cycles too quickly to really make any difference.
---------- Post added at 01:35 PM ---------- Previous post was at 01:31 PM ----------
Phase is just a term for where a waveform is in its cycle. If you have two sinewaves that begin and end a cycle at the same time, they're going to double the amplitude. if you move one of these 180 degrees out of phase, the waves will be in exact opposition and completely cancel eachother out (in theory... there's no such thing as perfect cancellation, or even perfect sine waves for that matter.)
Phase has nothing to do with key, pitch, tamber, etc. But moving two signals out of phase from eachother slightly CAN effect those things... it just depends on the sound and depends on the application and depth of the changes to a signal's phase you're applying.
Positive side of a waveform (the top side) is the amount the speaker moves away from the driver (compression), while the bottom side is the distance the speaker pulls back to complete the cycle (rarefaction). Reversing these doesn't necessarily effect the quality of a sound, but if there's a large initial punch, you can usually tell if that first smack is compression or rarefaction. This is typically only done on low-frequency percussive sounds. High frequencies complete cycles too quickly to really make any difference.
---------- Post added at 01:35 PM ---------- Previous post was at 01:31 PM ----------
Phase is just a term for where a waveform is in its cycle. If you have two sinewaves that begin and end a cycle at the same time, they're going to double the amplitude. if you move one of these 180 degrees out of phase, the waves will be in exact opposition and completely cancel eachother out (in theory... there's no such thing as perfect cancellation, or even perfect sine waves for that matter.)
Phase has nothing to do with key, pitch, tamber, etc. But moving two signals out of phase from eachother slightly CAN effect those things... it just depends on the sound and depends on the application and depth of the changes to a signal's phase you're applying.
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