During the last days I've been using a sine wave generator ("SineGen") to find peaks in my headphones and equalize them. Yesterday I noticed that this software has an option to adjust the phase of the wave, and I decided to try it out. I did several tests moving the slider with my eyes closed trying to center the sound and I always got a similar value, far from the default of zero degrees! Something was wrong...
To see if it was the headphones, I first centered the sound moving the slider and then I flipped my headphones so the left driver was in the right ear and vice versa. After doing this I noticed the audio was now very offset, suggesting it was not the headphones but my ears instead. To confirm this, I got other headphones and I repeated the blind test... I was getting very similar values with the phase slider. My ears are out of phase!! I have never seen anyone talk about this issue before. Maybe it's because my ear canals don't measure the same or my eardrums are different? I have no idea.
I had always heard slightly differently with my left and right ears. The left one was always louder and had more "resolution". No matter how much I adjusted the decibels in each channel, I wasn't able to fix the stereo image. The vocals were always a bit displaced to the left side. Our brains are very sensitive to phase, especially under 1 kHz. You can't trick the brain only changing the amplitude. After finding this out, I have added a delay corresponding to the degrees of phase shift to one of the audio channels and... although my ears aren't still perfect, the stereo image has improved A LOT! I can finally hear the vocals exactly in the center! I'm quite happy now!
If anybody wants to try this out, I'm writing here a tutorial:
(This is mainly for headphones. In speakers everything is a little different and I don't know if it would be a good idea to change the phase. You can try it and tell me):
1. Download SineGen (or use a similar program). SineGen is freeware but the original website doesn't exist anymore. You can find and download it on a website called "LO4D".
2. In "Frequency" (red arrow) write "500". I think this frequency could be the best option for testing, since it's one of the most sensible frequencies to phase mismatch and it's also important for vocals imaging.
3. Now click on "Power". You will hear a 500 Hz sine wave. Adjust the volume to pleasant levels, click on the "Phase Difference" slider (green arrow) and move it around until you perfectly center the sound in your head. I personally prefer to close my eyes and sometimes I touch the tip of my nose with a finger in order to better focus on the center of my head.
4. If you do a couple of tries and you get very close to 0º (±5º) then your ears and headphones are perfect! If you get a bigger value (I was getting always around 23º) then you should test if it's the headphones or your ears! To check this you can flip the headphones or try another headphones. If it's just the headphones, check if it's only affecting certain frequencies, since the difference could be negligible in general listening. If your headphones are still under warranty, you could return them.
5. If you want to fix the phase mismatch you will need an equalizer. I'm using Equealizer APO for this. First you need to translate your degrees of phase difference to milliseconds of delay. You can use an online "phase shift calculator". Remember to use here the same frequency that you used in SineGen (e.g. 500 Hz). For example, you'll need 0.156 ms of delay in order to fix a 28º phase difference.
6. Add the delay to your EQ and load it in Equalizer APO. If you got a positive degree value in SineGen, then you'll need to add the delay to the left channel. If you got a negative value, you'll need to add the delay to the right channel instead. Apply the equalization file and check it out. If it's not perfect try again until you find the best delay for you.
NOTE: The "delay" filter doesn't seem to work with "Peace GUI", but it's working with the stock "Configurator Editor" of Equalizer APO.
In order to further improve your correction, you can use mono music (e.g. using the "Downmix channels to mono" DSP in foobar2000) and tune the ms delay a bit. I added/removed 0.01 ms each time and checked the results with mono music until I found the best match for my ears.
Note: Sometimes headphones can have a phase mismatch in certain frequencies but behave correctly with the rest of them. If your headphone has a phase shift in your testing frequency (e.g. 500 Hz) and you use this method, you'll change the phase for all the frequencies and you may get worse imaging than before. That was not my case though!
If anyone knows a better way to do this (e.g. correct the phase of other frequency ranges as well), I'd appreciate it. With this method very low frequencies are still a bit out of phase to my ears, but despite this the improvement after using the delay is still huge!
To see if it was the headphones, I first centered the sound moving the slider and then I flipped my headphones so the left driver was in the right ear and vice versa. After doing this I noticed the audio was now very offset, suggesting it was not the headphones but my ears instead. To confirm this, I got other headphones and I repeated the blind test... I was getting very similar values with the phase slider. My ears are out of phase!! I have never seen anyone talk about this issue before. Maybe it's because my ear canals don't measure the same or my eardrums are different? I have no idea.
I had always heard slightly differently with my left and right ears. The left one was always louder and had more "resolution". No matter how much I adjusted the decibels in each channel, I wasn't able to fix the stereo image. The vocals were always a bit displaced to the left side. Our brains are very sensitive to phase, especially under 1 kHz. You can't trick the brain only changing the amplitude. After finding this out, I have added a delay corresponding to the degrees of phase shift to one of the audio channels and... although my ears aren't still perfect, the stereo image has improved A LOT! I can finally hear the vocals exactly in the center! I'm quite happy now!
If anybody wants to try this out, I'm writing here a tutorial:
(This is mainly for headphones. In speakers everything is a little different and I don't know if it would be a good idea to change the phase. You can try it and tell me):
1. Download SineGen (or use a similar program). SineGen is freeware but the original website doesn't exist anymore. You can find and download it on a website called "LO4D".
2. In "Frequency" (red arrow) write "500". I think this frequency could be the best option for testing, since it's one of the most sensible frequencies to phase mismatch and it's also important for vocals imaging.
3. Now click on "Power". You will hear a 500 Hz sine wave. Adjust the volume to pleasant levels, click on the "Phase Difference" slider (green arrow) and move it around until you perfectly center the sound in your head. I personally prefer to close my eyes and sometimes I touch the tip of my nose with a finger in order to better focus on the center of my head.
4. If you do a couple of tries and you get very close to 0º (±5º) then your ears and headphones are perfect! If you get a bigger value (I was getting always around 23º) then you should test if it's the headphones or your ears! To check this you can flip the headphones or try another headphones. If it's just the headphones, check if it's only affecting certain frequencies, since the difference could be negligible in general listening. If your headphones are still under warranty, you could return them.
5. If you want to fix the phase mismatch you will need an equalizer. I'm using Equealizer APO for this. First you need to translate your degrees of phase difference to milliseconds of delay. You can use an online "phase shift calculator". Remember to use here the same frequency that you used in SineGen (e.g. 500 Hz). For example, you'll need 0.156 ms of delay in order to fix a 28º phase difference.
6. Add the delay to your EQ and load it in Equalizer APO. If you got a positive degree value in SineGen, then you'll need to add the delay to the left channel. If you got a negative value, you'll need to add the delay to the right channel instead. Apply the equalization file and check it out. If it's not perfect try again until you find the best delay for you.
NOTE: The "delay" filter doesn't seem to work with "Peace GUI", but it's working with the stock "Configurator Editor" of Equalizer APO.
In order to further improve your correction, you can use mono music (e.g. using the "Downmix channels to mono" DSP in foobar2000) and tune the ms delay a bit. I added/removed 0.01 ms each time and checked the results with mono music until I found the best match for my ears.
Note: Sometimes headphones can have a phase mismatch in certain frequencies but behave correctly with the rest of them. If your headphone has a phase shift in your testing frequency (e.g. 500 Hz) and you use this method, you'll change the phase for all the frequencies and you may get worse imaging than before. That was not my case though!
If anyone knows a better way to do this (e.g. correct the phase of other frequency ranges as well), I'd appreciate it. With this method very low frequencies are still a bit out of phase to my ears, but despite this the improvement after using the delay is still huge!
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