If I have two lines (for example, two bass lines that one of them is inverted one of the other), after I mono the track, (for example listen it on my mobile phone), these two lines will cancel each other, and I wont be able to hear any bass sound. but is that the only side effect? I mean, is there a chance that this anti-phase problem, create some kind of bad distortion or something?

2 Answers 2


Phase cancellation is a phenomenon that sound engineers usually address during mixing and recording to minimize its impact on normal listening conditions, including mono outputs. It’s mostly a concern for electronic instruments that use samples or synthesis to create sounds with fixed pitches and phase. Acoustic instruments have fewer problems with phase, because the sounds they produce have a much greater variability in phase and pitch even when nominally playing in unison. Instead of phase cancellation, you normally get a “chorus” sound from acoustic instruments.

That said, electronic pickups & microphones can still cause some phase problems even with acoustic instruments, especially if you use stereo microphone configurations. Again, this is a problem that recording engineers test for and resolve, either at performance time or at mixing time. If your final mix ends up phase-canceled, then the recording or mixing engineer made a mistake, presuming it wasn’t done for deliberate artistic effect.

Artists do occasionally use phasing for artistic effect, in which case you typically get the sound of a phaser or flanger, two common effects for electronic guitars and keyboards.

If you mix your own music, and you don’t control for phase, then you will see unpredictable results ranging from weak drum hits to random volume fluctuations to weird filtering effects. You don’t even need to reduce a stereo mix to mono to hear this; simply mixing down multiple mics or tracks into one stereo channel can cause it.

  • thanks. but maybe i asked badly.for example i want to stereo wide my pad sound, i use that alot, coz it has some cool stereo sound. i use s1 imager , now it sound nice and wide on my monitoring speakers, but when i use analyzer it has a lot of anti phase problem. i want to know if i master and listen it on my mobile, does it have any other side effect problem beside reducing the pad sound volume??? thanks alot
    – dana
    Jan 23, 2018 at 22:37
  • I’m not totally sure what you’re asking, but I think you are running into the sort of problems that my two links talk about. If you don’t correct it, then you will likely get weird artifacts like phasing & flanging (caused by the underlying comb filtering mentioned in another answer). Best case, you’ll get weak drum sounds and random volume cut-outs. Layered & stereo drum effects are especially prone to this, so you should fix it in mixing. Jan 23, 2018 at 22:41
  • I added a paragraph to address what results you are likely to get if you don’t control phase in your mixes. Jan 23, 2018 at 22:50
  • @dana By the way, I recommend editing some of that detail into your question, so that any additional answers can get to the root of what you want to know. Especially the parts about making your own mixes and getting phase warnings from your DAW. Jan 23, 2018 at 23:01
  • i dont know how to add any other detail.i mean. its simple.i just dont know how to say that.you know there are lot of plugins that could stereo wide your sound image.like waves s1 and izotope imager. but when you use them (and if you push them hard to get wider sound) you will end up having anti phase issue( you could see this anti phases on any analyzer) . well i think that in digital music, anti phase isnt a problem on stereo speakers, but when we listen the music on mono devices, we see the problem,coz it will reduce the sound of anything that have anti phase.but is there other side effect?
    – dana
    Jan 23, 2018 at 23:12

Comb filtering.

If the two basslines are exactly the same and you invert the phase 180 degrees then yes they will cancel out. But in a lot of real world scenarios you might not be dealing with that theoretical purity. You might have two microphones that are picking up the same thing at slightly different distances for example.

So at times the waves will align and at times they won't causing a mix of adding and subtracting to the combined signal. The auditory effect of that is called "comb filtering" and you can search YouTube to hear what it sounds like.

  • aha. thank you. so you say that it only create phase cancellation when it is inverted 180 degree. and the other time it doesnt make real problems( i mean the times when some of my signals are out of 90 degree range and my correlation meter start to go down the zero to -1 ) (i mean it happen briefly but not all the time.) am i right?
    – dana
    Jan 24, 2018 at 10:47
  • 2
    @dana no, you get partial cancellation and comb filtering effects with complex signals whatever the phase difference is - it's just that only the 180 degree difference will result in complete cancellation. Jan 24, 2018 at 12:38
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    I was about to answer exactly this. This is the most common problem with phase mis-alignment. @dana Comb filtering happens at all phase misalignments. As the phase is changed, the frequencies cancelled out by the comb filter change. That is what a phaser effect or pedal does. Only when the sounds are perfectly synchronized or separated by a phase that is too large does the comb filtering go away. In the case of a very large phase difference, the comb filtered frequencies are outside of the range of human hearing so they don't matter. Jan 24, 2018 at 16:27

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