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is phase checking necessary? Direct Injection & Re-amp Boxes
Old 20th March 2010
  #1
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payne104's Avatar
is phase checking necessary?

If you're recording everything to seperate tracks in pro tools... doesn't it make sense to align the phase of some things in pro tools, after you have recorded, once you can see whats going on with the waveform....

what's all the fuss about getting the phase right during tracking... it doesn't seem worth the worry for something like guitar cab and DI
Old 20th March 2010
  #2
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narcoman's Avatar
 

cus you cant really change the phase once it's done. It's about mic positions.
Old 20th March 2010
  #3
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gear is cool's Avatar
Getting the phase right before it's recorded is very important.
If you do it before there is no need to "worry" about doing it later.
Although I tend to double check when setting up for a mix.
Simply aligning tracks after doesn't fix the phase issues.
Maybe Jonathan Little could chime in about the technical reasons why this is so.
One reason NOT to align them after is the distance between, say your overheads to the kick is the distance between them gives the kit its natural sound. I would would never move the overheads/rooms to hit right with the kick drum. There would be no room for air to breath.
The distance between them is what makes the kit come alive.
Sometimes its hard to hear to difference between say the snare when you have the kick and oh's in.
A trick I learned hear actually is to boost the low end eq on snare to find it, then disengage the eq
-Joe
Old 20th March 2010
  #4
Quote:
Originally Posted by StudioDan View Post
PS: Lots of engineers tend to look at techniques like a dichotomy (a full-stop yes or no), instead of a science full of many minor details. Beware of simple responses, research how sound works, and craft technique through a mixture of education, skepticism, logic, and experience. This is art, so let your emotion guide your love for it,
Yeah, yeah, yeah.
But don't you think this simple answer is just basically right......
Get the best drum sound you can at the moment you record it.
Afterwards, if you can improve on it all the better.
But saying it'll do we can fix it later is the worst way to go about recording.
So it is very simple in a way.
Get a good sound from the first moment (mic choice, mic position, position of the instrument in the room).
Everything else is icing on the cake.
Old 20th March 2010
  #5
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Quote:
Originally Posted by payne104 View Post
once you can see whats going on with the waveform....
See..? Are you a graphic designer?
Old 20th March 2010
  #6
Gear Maniac
 

Yeah, totally unimportant. They got a plug-in for that right?

Try going a week without wiping...see what happens.

Ok, seriously they're are too many reasons to go into it here...but, YES PHASE COHERENCY IS VERY IMPORTANT!!!

Unless, of course, you don't care and whoever mixes your material has a rack full of Little Labs IBP's...then don't worry about it.

Nudging tracks in protools will not get tracks to sound right, in fact it will just make matters worst.

JMHO, proceed at your own risk.



Nathan.
Old 20th March 2010
  #7
Gear Maniac
 

As always the answer is "it depends". Drums can be tricky to fix, but I've had a lot of luck fixing phasey DI and amp bass tracks in Tools. Some phase problems can be fixed by ditching unnecessary tracks to start with - who really needs 6 mics on a guitar amp, for instance?
Old 20th March 2010
  #8
Gear Maniac
 

To StudioDan, sorry I should have phrased it: "in most cases it will make matters worse." Thanks.

In most cases (98%) of the time I've found that simply nudging wont get you there. Just as plug in phase "switches" don't seem to sound as good as the 180 deg. switches on an analog console.

hibakusha: those are usually the situations that i resort to nudging on tracks.


My point is not checking phase with your EAR's is a huge problem with recording(s) today as there is an ignorance to the importance of phase coherency.

ok, fire up the flame throwers...lol

Nathan.
Old 20th March 2010
  #9
Quote:
Originally Posted by StudioDan View Post

Is it really necessary to make such bold claims? It CAN make things worse, but it depends on what you are moving!

I'm thinking about writing a song called "Audio Dichotomy" now... lol
(that's a logical fallacy btw... hint hint)
Whilst you made some very good points in your detailed post Dan, the OP said "what's the fuss - can't you fix it afterwards?!" which shows a total misunderstanding about the difference between phase and time aligning, and a lack of experience.

Your post delves into a lot of advanced techniques, when the OP really needs to be told "yes - it's VERY important!". You need to learn the rules before you can break them (ie walk before running) - and I don't think the OP is at that point yet.
Old 20th March 2010
  #10
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trondned's Avatar
 

Even if we tend to call it "rules" it really is more of a guide. Like if you're learning a C major scale on your guitar - doesn't mean you're not allowed to use other notes in your music.

I agree that it's ok to nudge a two-mic recording of a guitar-amp. But multi-micd drums are too complex for any of us to foresee the result of doing so. One of the reasons it's best to get it right when recording is because when you realign the snare for instance, to make better phase-relationship with the overheads, you'll make things change between the snare and hi-hat. If you wanna record a bad sounding kit and just say "I'm sure I can fix it later by nudging tracks" I'd say go ahead, but it's not very professional. A professional wants to take the guesswork, the hopes and the prayers out of the equation.

If you then want to experiment with nudging on a copy of the session, go ahead. If it makes the result even better - great. All I know is I wouldn't sleep well at night if I sent the drummer home and had a crap sound "on tape".
Old 20th March 2010
  #11
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Sigma's Avatar
if we brought a tape measure in the studio to measure distance between mics we woulda been laughed outta the business..

1/2 the time when i was an assistant , the engineers never even looked or asked about a mics placement unless when they pushed up the fader it sounded wrong to them
Old 20th March 2010
  #12
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Sigma's Avatar
Quote:
Originally Posted by zboy2854 View Post
Same here. IME, the process was always, put the mics up, bring up the faders one at a time. If the next fader up diminished the sound at all or didn't add body or punch to the sound, hit the polarity reverse button or move the mic, whichever worked. Rinse and repeat.
exactly..
Old 20th March 2010
  #13
Quote:
Originally Posted by Joe Porto View Post
Well, I actually use a patch cord to measure distance, I do this with OHs to insure the snare is in the middle of the stereo field, and I also do this when micing multiple guitar amps with a single distance mic. And to be honest, I wouldn't care if someone laughed at my process, because it works.
Ditto. Sometimes things sound ok before you check phase, then you flip the snare against the OHs, and it sounds even better.

Quote:
Originally Posted by trondned View Post
Even if we tend to call it "rules" it really is more of a guide. Like if you're learning a C major scale on your guitar - doesn't mean you're not allowed to use other notes in your music.

I agree that it's ok to nudge a two-mic recording of a guitar-amp. But multi-micd drums are too complex for any of us to foresee the result of doing so. One of the reasons it's best to get it right when recording is because when you realign the snare for instance, to make better phase-relationship with the overheads, you'll make things change between the snare and hi-hat. If you wanna record a bad sounding kit and just say "I'm sure I can fix it later by nudging tracks" I'd say go ahead, but it's not very professional. A professional wants to take the guesswork, the hopes and the prayers out of the equation.

If you then want to experiment with nudging on a copy of the session, go ahead. If it makes the result even better - great. All I know is I wouldn't sleep well at night if I sent the drummer home and had a crap sound "on tape".
Totally agree. Of course there's no "rules" - but to use your learning music simile, it generally helps to learn the "sound" of a major scale to be able to write and play music - it helps in all areas. Of course there are the exceptions, people born with an inherent musical genius, but for us mortals it's pretty useful.
Old 20th March 2010
  #14
ark
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You can't fix phase errors by nudging tracks, because that will affect the phase of different frequencies differently. If you have a way of inverting the phase of a track after you've recorded it, I can't see any reason that the effect wouldn't be the same as that of inverting the phase after you've recorded it.

However...As a general rule, the earlier in a multi-step process you fix a problem, the less of a problem it is. In other words, the easiest way to deal with a phase problem is to get the phase right in the first place. If you can't do that, the second easiest way to deal with it is to correct the track's phase (i.e. invert it) as soon as possible after recording.
Old 20th March 2010
  #15
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doorknocker's Avatar
Quote:
Originally Posted by payne104 View Post
what's all the fuss about getting the phase right during tracking? Am I missing something???
Check everythign in mono on one-speaker, especially things like multi-miced drums and guitar cabs. But remember that the punchiest sound is not also the best one.
Old 20th March 2010
  #16
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evangelista's Avatar
 

I wouldn't say that recording a drum set with more than one mic is natural in the first place. So nudging tracks doesn't really seem like that much of a departure in philosophy.

That's not to say I nudge tracks as a matter of course, but I've done it when it yielded desirable results. Just get the mix done, move on with your life.
Old 20th March 2010
  #17
Quote:
Originally Posted by zboy2854 View Post
Same here. IME, the process was always, put the mics up, bring up the faders one at a time. If the next fader up diminished the sound at all or didn't add body or punch to the sound, hit the polarity reverse button or move the mic, whichever worked. Rinse and repeat.
+1,000!! Gosh, how the heck did those guys back in the 50's, 60's, and 70's get their tracks phased properly without a waveform to look at??

Uhhhhh... they used their ears and their knowledge of what phase anomalies occur in multi-mic situations!

Once I've got my tracks sounding good, I've never looked to see what the waveforms do in relation to each other. Don't get me wrong, there's plenty of times where looking at the waveforms comes in handy (editing, punch-ins, etc.), but if the track sounds good, then that's the end of it. The advent of DAW's and graphic representations of waveforms seems to me to have made recording and mixing more of a VISUAL exercise than a AURAL exercise. Don't get bogged down by the details. Just my opinion though.
Old 20th March 2010
  #18
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Quint's Avatar
Quote:
Originally Posted by hibakusha View Post
As always the answer is "it depends". Drums can be tricky to fix, but I've had a lot of luck fixing phasey DI and amp bass tracks in Tools. Some phase problems can be fixed by ditching unnecessary tracks to start with - who really needs 6 mics on a guitar amp, for instance?
Bass DI is a lot easier to do this with because the DI signal didn't involve a microphone. With mic'ed signals it isn't as easy to just slide a track over in the computer.
Old 20th March 2010
  #19
Quote:
Originally Posted by Quint View Post
Bass DI is a lot easier to do this with because the DI signal didn't involve a microphone. With mic'ed signals it isn't as easy to just slide a track over in the computer.
It's exactly the same situation - I'm assuming the bass cab has a mic on it?! i anything, it's MORE significant, at least the drum pitches stay relatively consistent - the bass line won't and the phase issues will change as the pitch changes.
Old 20th March 2010
  #20
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Quint's Avatar
Quote:
Originally Posted by psycho_monkey View Post
It's exactly the same situation - I'm assuming the bass cab has a mic on it?! i anything, it's MORE significant, at least the drum pitches stay relatively consistent - the bass line won't and the phase issues will change as the pitch changes.
Enlighten me on this. I'm not necessarily saying your wrong (although I think I'm right heh), I'd just like to hear your opinion on this. I totally understand how multi-miced sources are ripe for phase issues as I do the majority of my recording in a "band live in the room" setting and take a lot of care to make sure things are in phase. However, a DI signal involves no acoustic information. I don't see what the big problem is with moving the DI track to align with the mic'ed amp track? I haven't noticed near the problems in the bass DI scenario with phase as I've noticed in other situations.
Old 20th March 2010
  #21
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Sigma's Avatar
Quote:
Originally Posted by Joe Porto View Post
Well, I actually use a patch cord to measure distance, I do this with OHs to insure the snare is in the middle of the stereo field, and I also do this when micing multiple guitar amps with a single distance mic. And to be honest, I wouldn't care if someone laughed at my process, because it works.

Anyway, I'm glad you got your little morning jolt of superiority. I'm sure you needed it.
dude you are welcome to wear a tutu and chant druid prose while setting up mikes for all i care
Old 20th March 2010
  #22
Gear Nut
 

Correct me on this one if I'm wrong, but what I've always learned is:

Every sound consists of a lot of frequencies, every frequency has got it's own wavelength. 1Khz for example has a wavelength of 34 cm. 10Khz has a wavelength of 3.4cm. So if you move the TOTAL audio signal (the track in you DAW) that consists of all those frequencies together, you can align the phase of 1 frequency (or a range, more or less) but you will create problems with the other frequencies! In order to shift the "waveposition" of all the frequencies to the same degree, you will need the Little labs or a plugin like phasebug.
Old 20th March 2010
  #23
Gear Nut
 

Let my clarify that using the attached image.

Both waves are from the same track (i.e. rhythm guitar). A and B are both moments in time.
If you move your track from A to B, the low frequency shifts (roughly) from +90 to -90, which is a 180 degree phase shift.
The higher frequency shifts from -80 tot 0 degrees, resulting in a 80 degree phase shift. So when you move in time, you don't shift the phase equally for all frequencies!
The correct way is not to move from A to B, but to shift the phase of both frequencies by the same amount.
Attached Thumbnails
is phase checking necessary?-phase.jpg  
Old 20th March 2010
  #24
Quote:
Originally Posted by Quint View Post
Enlighten me on this. I'm not necessarily saying your wrong (although I think I'm right heh), I'd just like to hear your opinion on this. I totally understand how multi-miced sources are ripe for phase issues as I do the majority of my recording in a "band live in the room" setting and take a lot of care to make sure things are in phase. However, a DI signal involves no acoustic information. I don't see what the problem is with moving the DI track to align with the mic'ed amp track?
I'm pretty certain you're not

If what you said was true, you'd also be able to line up 2 mics on one source the same way (eg one mic 10cm away, one 15cm away, work out the time delay). However, we all know that causes problems. the difference in sources is 5cm, and so you can work out the time delay. But read twilight's post to see how you can't just time align one transient and expect the phase to stay the same for all frequencies.

Now physics doesn't differentiate between sources. Your DI is simply another soundwave, no different to the mic'd source in principle, but with a distance of 0cm from the source - so the distance between that and our 2 mics are 10cm and 15cm respectively. Thus you have exactly the same phase issues. If you really wanted to be anal about it, you could time align the transient attack of each source (which SHOULD stay constant), and use a phase adjuster like the LL box to get the best phase alignment. Alternately, use mic placement and your ears in the first place and get a solid tone, and don't fuss about.
Old 20th March 2010
  #25
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narcoman's Avatar
 

Quote:
Originally Posted by StudioDan View Post
That answer is too simplistic IMHO.
No - that answer is spot on. You can only change phase problem with a phase changing device or plugin like L.Labs device. And even then - it's not a cover all. The most appropriate thing to do is to get things as right as "sounds right" at source. Fixing stuff is for those of us who have to work with bad recordings from those who don't know what they are doing.

Get phase "problem" sorted at source. If they're not problems then fine.
Old 20th March 2010
  #26
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narcoman's Avatar
 

Quote:
Originally Posted by ark View Post
You can't fix phase errors by nudging tracks, because that will affect the phase of different frequencies differently. If you have a way of inverting the phase of a track after you've recorded it, I can't see any reason that the effect wouldn't be the same as that of inverting the phase after you've recorded it.

However...As a general rule, the earlier in a multi-step process you fix a problem, the less of a problem it is. In other words, the easiest way to deal with a phase problem is to get the phase right in the first place. If you can't do that, the second easiest way to deal with it is to correct the track's phase (i.e. invert it) as soon as possible after recording.
yup
Old 21st March 2010
  #27
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Quint's Avatar
Quote:
Originally Posted by psycho_monkey View Post
I'm pretty certain you're not

If what you said was true, you'd also be able to line up 2 mics on one source the same way (eg one mic 10cm away, one 15cm away, work out the time delay). However, we all know that causes problems. the difference in sources is 5cm, and so you can work out the time delay. But read twilight's post to see how you can't just time align one transient and expect the phase to stay the same for all frequencies.

Now physics doesn't differentiate between sources. Your DI is simply another soundwave, no different to the mic'd source in principle, but with a distance of 0cm from the source - so the distance between that and our 2 mics are 10cm and 15cm respectively. Thus you have exactly the same phase issues. If you really wanted to be anal about it, you could time align the transient attack of each source (which SHOULD stay constant), and use a phase adjuster like the LL box to get the best phase alignment. Alternately, use mic placement and your ears in the first place and get a solid tone, and don't fuss about.
Well bass is the only instrument I ever take a DI of and, if needed (lots of times it's not), I just slide it over to match the amp track and I've never had any issues with phase. I guess my point about bass DI was based on two things. First, a DI signal is essentially like having a mic zero distance from the source (all freq. waves hitting the "mic" at a starting point of phase equal to 0). That combined with the relatively long wavelengths of bass signals and the short distance between the amp and mic means that there is literally less room for things to get out of phase, enough anyway, so that I don't worry about it too much. I generally just use my ears and go with what sounds best. I have been known to use a tape measure or string on overheads for the Recorderman technique though. heh

What you and twilight are saying is correct and I don't disagree. I understand that simply sliding a track won't correct phase issues and can, in fact, cause more phase issues. I'm simply saying that, for the limited amount of sliding of tracks that I do, I haven't noticed any real issues in those limited scenarios, hence my response only pertained to bass DI. As simple as it is, the graphic and short explanation that Twilight posted is really all that the OP needs to see why phase and time alignment are two different things.
Old 21st March 2010
  #28
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rocksure's Avatar
Quote:
Originally Posted by Joe Porto View Post
Well, I actually use a patch cord to measure distance, I do this with OHs to insure the snare is in the middle of the stereo field, and I also do this when micing multiple guitar amps with a single distance mic. And to be honest, I wouldn't care if someone laughed at my process, because it works.

Anyway, I'm glad you got your little morning jolt of superiority. I'm sure you needed it.
I totally agree. I always use a cable or string to measure the distance from the overheads to the snare to keep it in the middle. I even do it with room mics to keep the distance from the snare consistent with the overheads (ie: usually double or four times).
No one has ever laughed at it, infact the precision usually gives them confidence that you know what you are doing ( or at least appear to lol).
Old 21st March 2010
  #29
Quote:
Originally Posted by Quint View Post
Well bass is the only instrument I ever take a DI of and, if needed (lots of times it's not), I just slide it over to match the amp track and I've never had any issues with phase. I guess my point about bass DI was based on two things. First, a DI signal is essentially like having a mic zero distance from the source (all freq. waves hitting the "mic" at a starting point of phase equal to 0). That combined with the relatively long wavelengths of bass signals and the short distance between the amp and mic means that there is literally less room for things to get out of phase, enough anyway, so that I don't worry about it too much. I generally just use my ears and go with what sounds best. I have been known to use a tape measure or string on overheads for the Recorderman technique though. heh
Well, if it works for you like this in practice, that's great.

However, there's still several points of inaccuracy above:

the fact that the DI is has a zero "delay" means nothing - it's the time delay between the sources that is important. Effectively with 2 mics, the first one has a zero "delay" - again, physics doesn't care where the sound capture device is in relation to the initial source, only in the relationship between multiple devices be they DI or mic.

secondly, though the fundamental of a bass sound might be a relatively long wavelength, the overtones certainly won't be. whether you hear this as a problem is another thing.

lastly, close micing a bass amp isn't always the best approach - sometimes that can cause more phase problems than a mic with a bit more space (and often bass sounds better miced at a bit more of a distance).

Again if it sounds right, don't worry about it. I also don't - I set up mic and DI, get a nice mic sound, get a nice DI sound, flip polarity, move mic back and forwards in small increments until I get the thinnest sound, flip polarity and that's generally a good sound.
Old 21st March 2010
  #30
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Quint's Avatar
Quote:
Originally Posted by psycho_monkey View Post
Again if it sounds right, don't worry about it. I also don't - I set up mic and DI, get a nice mic sound, get a nice DI sound, flip polarity, move mic back and forwards in small increments until I get the thinnest sound, flip polarity and that's generally a good sound.
This is exactly how I do things as well. Always seems to work for me. Flipping the polarity and finding the thinnest sound helps to take some of the subjectivity out of it for me so that I don't continue to wonder if a better sound was achievable. Granted, it's all subjective but the polarity flip helps to give me peace of mind and find the sound I want quickly.
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