G
Gabriel Sousa
New member
Hello, what is phase problems ? can i ear it ? can i fix it ?
thanks
thanks
dachay2tnr
One Hit Wonder
I'll try from a non-techies point-of-view. I'm sure someone will come along and tell you if I'm full of s*&t.
I presume that you are aware if you take a sound signal and reverse the phase of it and then play the two signals together, you will get nothing. No sound. In other words, the two signals will cancel each other out because they are completely out of phase with each other.
Well you can kind of get a partial effect of the same thing when recording the same source from multiple inputs (e.g., two mics on a guitar). If the mics are not the same distance from the source, the sound signal will reach each one at a different time. When that happens it is possible for some of the frequencies to cancel each other because of the differenet phasing, resulting in a "thin" sound, because you are not getting all the frequencies that the source put out.
So, yes, you can hear it.
I presume that you are aware if you take a sound signal and reverse the phase of it and then play the two signals together, you will get nothing. No sound. In other words, the two signals will cancel each other out because they are completely out of phase with each other.
Well you can kind of get a partial effect of the same thing when recording the same source from multiple inputs (e.g., two mics on a guitar). If the mics are not the same distance from the source, the sound signal will reach each one at a different time. When that happens it is possible for some of the frequencies to cancel each other because of the differenet phasing, resulting in a "thin" sound, because you are not getting all the frequencies that the source put out.
So, yes, you can hear it.
fprod south
Member
If you're working in digital try this. Record a track. Duplicate it. Then slide the duplication forward by about 50-100 samples. I think the best adjective to describe the sound you will hear is "hollow".
G
Gabriel Sousa
New member
thanks fprod south, but can a EQ, reverb or compresser plugin cause it ? can i fix a phase problem ? there are plugins to see if there are phase problems ?
thanks
thanks
fprod south
Member
Fixing phase problems is a bit over my head so hopefully someone else can help out.
But plug-ins can cause phase problems because the processing involved in the plug in will create some latency. I think the way to fix it would be to zoom in to sample level. Slide the track with the plug in back by a few samples. Look at the wave forms, but more importantly listen to make sure that the parts are lined up.
The only time I ever get this anal is when I re-amp. I record bass direct because I don't have a good bass amp. When I borrow a friend's amp, I send the direct bass part out and into the amp. I mic the amp and record it. I usually end up sliding the reamped part back by about 50-100 samples and it really makes a difference.
Sorry - I'm good at creating phase problems but don't know much about fixing them. I guess the best idea is to listen carefully as you're recording and move the mics around until you minimize the phase issues.
But plug-ins can cause phase problems because the processing involved in the plug in will create some latency. I think the way to fix it would be to zoom in to sample level. Slide the track with the plug in back by a few samples. Look at the wave forms, but more importantly listen to make sure that the parts are lined up.
The only time I ever get this anal is when I re-amp. I record bass direct because I don't have a good bass amp. When I borrow a friend's amp, I send the direct bass part out and into the amp. I mic the amp and record it. I usually end up sliding the reamped part back by about 50-100 samples and it really makes a difference.
Sorry - I'm good at creating phase problems but don't know much about fixing them. I guess the best idea is to listen carefully as you're recording and move the mics around until you minimize the phase issues.
C
chessrock
Banned
This is one of those things where it's tough to deny that DAWs have an edge over analog. One of the few instances, so give credit the few times it's due. 
Like FProd says, zoom in on the wave forms and line them up so the peaks and troughs match up as close as possible.
It's tougher to do it by ear, but the way you'd do it is slide the tracks around untill their combined volume is the loudest. When they're not lined up, the volume will decrease and/or it will sound like it has a phaser or chorus effect on it. For me, it's easier to just zoom in and do it visually.
Like FProd says, zoom in on the wave forms and line them up so the peaks and troughs match up as close as possible.
It's tougher to do it by ear, but the way you'd do it is slide the tracks around untill their combined volume is the loudest. When they're not lined up, the volume will decrease and/or it will sound like it has a phaser or chorus effect on it. For me, it's easier to just zoom in and do it visually.
fprod south
Member
I was intrigued so I looked this up. I use ProTools LE, but I imagine there's something similar with other software.
If you command click twice on the box that shows the volume level it shows how many samples the track is delayed due to plug ins. I checked it out and compressor, eq, and limiter all have a 2 sample delay.
And I also realized that you probably wouldn't be able to line up the waveforms by sight because I don't think you're seeing the processed wave form. I think you see it as it was recorded. When you reamp though you can line them up by sight.
Anyway...
If you command click twice on the box that shows the volume level it shows how many samples the track is delayed due to plug ins. I checked it out and compressor, eq, and limiter all have a 2 sample delay.
And I also realized that you probably wouldn't be able to line up the waveforms by sight because I don't think you're seeing the processed wave form. I think you see it as it was recorded. When you reamp though you can line them up by sight.
Anyway...
camn
Active member
its a real easy deal to visualize:
Imagine a wave from mic A.. .it starts at 0.. and goes up to 1 at a time=1ms.... then down to 0 at time =2ms... then down to -1 at time=3ms.... and back to 0 at time = 4 ms. heres a chart.
0ms...0
1ms...1
2ms...0
3ms...-1
4ms...0
5ms...1
6ms...0
NOW imagine you put a second identical mic roughly 1/500 of a foot behind the first. This gives you a wave offset 2ms... approx. it then looks like this:
0ms...0
1ms...-1
2ms...0
3ms...1
4ms...0
5ms...-1
6ms...0
SO... if you sum these two waves... you clearly get ZERO.
(be advised this is a simplified explanation.)
SOLUTIONS:
Mic things correctly.
Flip the offending waveform
Offset the offending waveform in time.
thank you,
xoxo
Imagine a wave from mic A.. .it starts at 0.. and goes up to 1 at a time=1ms.... then down to 0 at time =2ms... then down to -1 at time=3ms.... and back to 0 at time = 4 ms. heres a chart.
0ms...0
1ms...1
2ms...0
3ms...-1
4ms...0
5ms...1
6ms...0
NOW imagine you put a second identical mic roughly 1/500 of a foot behind the first. This gives you a wave offset 2ms... approx. it then looks like this:
0ms...0
1ms...-1
2ms...0
3ms...1
4ms...0
5ms...-1
6ms...0
SO... if you sum these two waves... you clearly get ZERO.
(be advised this is a simplified explanation.)
SOLUTIONS:
Mic things correctly.
Flip the offending waveform
Offset the offending waveform in time.
thank you,
xoxo
Light
New member
These posts are a little related, and should help you understand what phase is.
https://homerecording.com/bbs/showthread.php?threadid=62002
https://homerecording.com/bbs/showthread.php?threadid=57636
https://homerecording.com/bbs/showthread.php?threadid=59380
Can you hear phase issues? Sure. sum the two (or more) signals to mono, and then listen to them in stereo. If there are any phase issues, they will be very apparent.
Light
"Cowards can never be moral."
M.K. Gandhi
https://homerecording.com/bbs/showthread.php?threadid=62002
https://homerecording.com/bbs/showthread.php?threadid=57636
https://homerecording.com/bbs/showthread.php?threadid=59380
Can you hear phase issues? Sure. sum the two (or more) signals to mono, and then listen to them in stereo. If there are any phase issues, they will be very apparent.
Light
"Cowards can never be moral."
M.K. Gandhi
knightfly
GrouchyOldFartOnBatteries
Camn, you got the right idea except for the actual values - Since sound travels (in air at sea level at 70 degrees) at about 1135 feet per second, that means that it travels just over one foot per millisecond, so two milliseconds would be about 2.26 feet. Your example of 1/500 of a foot, would cause a delay of about 1/500 of a millisecond, or roughly 2 microseconds.
At 15 kHz, one cycle takes 66.6 microseconds to complete, so a 2 microsecond delay (in only one channel of a stereo source) would cause a phase shift (only at 15kHz, other freq's would be different) of just under 11 degrees. I doubt too many people would notice this small a phase change, at least in the context of an actual mix; perhaps while listening to test tones...
Still, the point is very valid that very small changes in mic location, whether micing in stereo or using two mics and blending the tracks, can cause phasing problems. These would usually be in the form of comb filtering, where different frequencies are affected differently. Some would be attenuated nearly to zero, while others would be either doubled or not affected, or anywhere in between. Small changes in the location of one mic can make large changes in the effect.
One important thing to remember is that phase relationships which are caused by timing delays, are DIFFERENT at EVERY frequency. This means that there is no constant condition that can compensate for phasing problems, such as the (mistakenly labeled) PHASE switch on a console strip.
For an example of what phasing sounds like, borrow an old guitar stompbox like the MXR Phase 90, and run your entire mix thru it. Cool for some effects, but not something you'd want to happen un-intentionally... Steve
At 15 kHz, one cycle takes 66.6 microseconds to complete, so a 2 microsecond delay (in only one channel of a stereo source) would cause a phase shift (only at 15kHz, other freq's would be different) of just under 11 degrees. I doubt too many people would notice this small a phase change, at least in the context of an actual mix; perhaps while listening to test tones...
Still, the point is very valid that very small changes in mic location, whether micing in stereo or using two mics and blending the tracks, can cause phasing problems. These would usually be in the form of comb filtering, where different frequencies are affected differently. Some would be attenuated nearly to zero, while others would be either doubled or not affected, or anywhere in between. Small changes in the location of one mic can make large changes in the effect.
One important thing to remember is that phase relationships which are caused by timing delays, are DIFFERENT at EVERY frequency. This means that there is no constant condition that can compensate for phasing problems, such as the (mistakenly labeled) PHASE switch on a console strip.
For an example of what phasing sounds like, borrow an old guitar stompbox like the MXR Phase 90, and run your entire mix thru it. Cool for some effects, but not something you'd want to happen un-intentionally... Steve
B
bleyrad
New member
i'm interested in hearing if anyone can explain what EQ phase problems sound like.
i've been toying around with trying to hear it whilst doing huge boosts, but i've never been able to say to myself, "yeah, i hear a phase shift delay of 18 degrees at 1000-1300Hz after i made that boost"
what exactly do EQ phase problems end up sounding like in a mix? smearing? general lack of tightness?
i've been toying around with trying to hear it whilst doing huge boosts, but i've never been able to say to myself, "yeah, i hear a phase shift delay of 18 degrees at 1000-1300Hz after i made that boost"
what exactly do EQ phase problems end up sounding like in a mix? smearing? general lack of tightness?
Light
New member
bleyrad said:
It does not work quite that way. What you will hear is a thinness and brittleness. What is happening is subtly different from multiple mic phase issues. What EQ does, more or less, is it slows down the higher frequencies. One of the things you will really notice is that transients will sound kind of blurred.
Hope that helps.
Light
"Cowards can never be moral."
M.K. Gandhi
camn
Active member
dammit, knightfly! I was hung over!
I meant 1/500th of 1135 feet .. of course! Thank you for your attention to detail!
the funny thing is.. when I was typing it.. i thought..
"1/500th of a foot?? isn't it 2 feet??"...
then I immediately thought...
"I'd like a bloody mary".
And there you go.
xoxo
I meant 1/500th of 1135 feet .. of course! Thank you for your attention to detail!
the funny thing is.. when I was typing it.. i thought..
"1/500th of a foot?? isn't it 2 feet??"...
then I immediately thought...
"I'd like a bloody mary".
And there you go.
xoxo
M
MartyMcFly
New member
TRY THIS!!!
take a track...dupliate it and patch a compressor (waves) or something that has a phase reverse button on it to both track. Its usually the O with a line thru it. Now click the button on one of the tracks. If your doing it right and you put your head right in the middle of your monitors it will actually make you a little dizzy.
TRY IT!!
take a track...dupliate it and patch a compressor (waves) or something that has a phase reverse button on it to both track. Its usually the O with a line thru it. Now click the button on one of the tracks. If your doing it right and you put your head right in the middle of your monitors it will actually make you a little dizzy.
TRY IT!!
C
chessrock
Banned
Try this . . .
Lie on the ground, belly-down, put your hands behind your head clasped together. Have a friend grab you and lift your head off the floor by your arms. Have him hold you there for 2 minutes. Now have him slowly let your head and arms back down in your original position.
It feels like your arms (and head) are sinking through the floor. Seriously, try it sometime.
Lie on the ground, belly-down, put your hands behind your head clasped together. Have a friend grab you and lift your head off the floor by your arms. Have him hold you there for 2 minutes. Now have him slowly let your head and arms back down in your original position.
It feels like your arms (and head) are sinking through the floor. Seriously, try it sometime.
B
bleyrad
New member
or, if you don't have any friends, but want to do the same sort of thing....
lie on your back on the floor. close your eyes. hold one arm straight up in the air above you, 90 degrees to your body. make a fist and clench it as tight as possible. tense up all the muscles in your arm, but try to keep the rest of your body relaxed. keep your arm tensed for a good minute or two, should almost be shaking from the pressure. then, keeping it tense, very, very slowly lower your arm towards the floor. keep your arm straight at the elbow - just bend at the shoulder. go really slow and keep your eyes closed and your arm tense. the whole "arm going down to the floor" thing should take a good 40 seconds or so. eventually it will feel like your arm descends right through the floor.
trippy shit.
lie on your back on the floor. close your eyes. hold one arm straight up in the air above you, 90 degrees to your body. make a fist and clench it as tight as possible. tense up all the muscles in your arm, but try to keep the rest of your body relaxed. keep your arm tensed for a good minute or two, should almost be shaking from the pressure. then, keeping it tense, very, very slowly lower your arm towards the floor. keep your arm straight at the elbow - just bend at the shoulder. go really slow and keep your eyes closed and your arm tense. the whole "arm going down to the floor" thing should take a good 40 seconds or so. eventually it will feel like your arm descends right through the floor.
trippy shit.
