Out of phase.

ICN

Bit of a technical novice here Guys - SO - apologies in advance for my basic way of describing this phenomenon!

Self taught all the way.. so there are definite gaps in my knowledge.


What confuses me is the whole "Out of phase" thing.


To explain..

When you have your track in Stereo, everything is grand on the surface.

When you go Mono - The volume halves & parts are missing.


Fair enough - It sounds grand in Stereo - why bother.. but surely something is really ****ing wrong when your track goes like that.


I know why it happens - Its out of phase! :pac:

I accept that it actually happens, as the evidence is there of course.. but I'd love to know how to fix it.


I always make sure that I am positioning my percussion slightly to one side.. Hats to the other.. A pad to the left, a noise to the right..

Nothing crazy.. Nothing would be panned hard left or right here.. I would rarely go past "a quarter past" or "a quarter to".

Kicks & (sometimes..) Claps/Snares are in mono & in the centre.

Basslines have no chorus, are in mono & in the centre.



Are there any best practices that can be used to prevent it?


If something is "Out of phase" as I've described.. How do you begin to resolve it?

Is it to do with "rogue" freq's clashing off each other? Just wondering.. as I can sometimes hear "comb-filtering" in evolving pads clashing with hats etc..

Apologies if the scattergun approach to getting to the root of something is being used Guys! Just trying to give you an "in-phase" image of whats going on


I use Logic Express - There is a phase meter in it.. & it shows a leaning to one side obviously - So its out of phase..the mono test proves it.. but I'm lost as to how to fix it.

Is this do-able? or is it like me asking how to do a DIY operation on the Brain surgery forum? LOL!

Possibly opening a whole can of worms here.

I've got a feeling that this is asking for a whole 101 on mixing etc.. :rolleyes:


I'm moving house @ the moment. Big relocation for us.. From Dublin to Roscommon. Anyway.. My whole life - literally - has been packed into boxes & is sitting in my new house, ready to be unleashed, sometime next week. Cant wait to get back to my Mac again. I've been spending the last few weeks, passing my time looking up "Music Stuff" on the Internet.. Mainly tutorials etc.. (not porn - :pac:)

I've tried Googling it.. but possibly have been searching really retardly for it & that is why I've got nowt useful back..

Any pointers Gentlemen?

PaulBrewer

Are you sure the speakers themselves are wired 'in phase'?

ICN

Thats simply making sure that the wires / polarity etc.. are correct, Yup?

If its that.. then yes, they are fine.

ogy

mono the entire track again and start panning again. you have to keep checking the phase as you mix, not just hope for the best at the end. If a pan position is causing phase cancellation in mono, you have to move it somewhere else!
its not neccesarily how wide or thin it is.

Remember also that you can flip the phase on tracks. If it is obvious from listening which tracks are causing the phasing (i.e. which ones are dissapearing or sounding washy when mono'd) flip the phase of one of the two instruments that are interfering with each other (not both obviously as this would keep the phasing in place:)).

Things that typically cause massive phasing problems are stereo widening effects and sometimes reverbs too, so check if the dry tracks still cancel

hope that helps!

Neurojazz

Just in laymens terms phasing = 2 parts in stereo field that occupy the same *frequency* and the same power - so maybe if you do mono/phase checks on effects busses, tracks together and tracks one by one etc... and then use a spectrum analyser to see what frequencies go when the phasing occurs... then you can eq that set of frequencies out from *ONE SIDE ONLY*.

The mono check is for radio - (Like the AM band) - that sums the track into mono for broadcast....

progsound

(information below is taken from another forum hope it helps you)

PHASE

"Right. There are two different things going on here: phase and polarity are only the same thing at one specific special-case point, really. Phase is a much more complex topic.

When two signals have exactly opposite voltages at each and every point in time, they are said to be "opposite polarity". They also happen to be 180deg out of phase with each other: that is the most gross phase error possible, and it happens to apply equally at all frequencies for this one special case. Add 'em together, you get zero: everybody knows that.

However, when you introduce *time* delays by spacing mics apart, the simple "opposite polarity" special case doesn't occur: because the sound takes time to go from here to there, and the wavelengths differ according to frequency, you have differing amounts of phase shift at different frequencies. This "different-phase-shift-per-frequency" thing is what gives you the "phasey" sound with a pair of mics at different distances from a source: you are creating a comb filter, where some frequencies are 180deg out of phase and cancel, and other frequencies aren't quite out and don't quite cancel, and others still are exactly in phase and *add* instead of cancel. What you really work with in mic placement is this parasitic comb filtering: it comes for free, because of the time delay.

Let's work an example, just for ****s and grins. Sound moves about 1100 feet per second (close enough for this example). So let's stick a pair of mics on a guitar amp: one right up against the cone, and one back a few feet. The picker graunches a chord, and the resulting signal has all sorts of components at different frequencies, from the lowest string's fundamental at 100Hz, say, all the way up to high harmonics up at 10kHz or so.

The wavelength of a 100Hz sine wave is 1100/100: 11 feet (nice, round number, eh?). So theoretically, to perfectly cancel that 100Hz out between the two mics, you'd put the second mic back 5.5 feet: one half wavelength. Ignoring reflections and all that unpleasant real-world dreck, when the pressure was just hitting its max positive value at the close-in mic, it'd just be hitting its max _negative_ value at the mic 5.5 feet away: one half wavelength, 180deg phase shift. With me so far?

Now let's look at some 1kHz stuff in the same signal. That 1kHz stuff has a much shorter wavelength: 1100/1000, or 1.1 feet (start to see the relationship?). So to completely cancel that 1kHz, you'd only have to move back .55 foot: 6.6 inches. The perfect cancellation distance for any given frequency is _not_ the perfect concellation distance for any other frequency, because the wavelengths differ. Make sense?

If we move the second mic back that 6.6 inches behind the first, we have 180deg phase shift (cancellation) at 1kHz, and only 18deg phase shift at 100Hz: not much at all, and very little cancellation. The 1kHz stuff covers 10 wavelengths in 1 single wavelength of 100Hz. That's the key!

So phase shift is a function of frequency, when you're talking about spacing between mics. In the first example there, that perfect cancellation of 100hz at 5.5 feet would give you a perfect _doubling_ at 200hz (360deg phase shift, or perfectly in phase), and a perfect cancellation at 300hz (540deg phase shift, or effectively 180deg out of phase) and so on: so you end up with a frequency response that has a series of peaks and notches in it. Thus the term "comb filter".

Changing the spacing moves the notches around, and that's what you are doing when you play with mic placement. It also changes the contributions of reflections and all sort of that real-world stuff sweetnubs mentioned that is really a damned sight more important than this nerdy theoretical ****. So you never get the precise cancellation or reinforcement that this contrived and oversimplified example might seem to predict: the comb filtering can be pretty subtle. But that's how it works."

ICN

Cheers Lads.. So that comb filtering effect that I can hear is actually phasing.

I wonder what that phasing sound could be? LOL :pac::pac:

Seriously - Lots of good food for thought there.

Wish I could go to my Mac & have a look.



I'll just number these follow-ups to keep it organised:

1.In order to fix the problem, is it just a matter of Eq'ing them correctly / applying a cut & leaving "the instrument" positioned where it is?

2.Or can you simply fix phasing by moving "the instrument" to +12R from +10R? and leaving the Eq as is, minus any surgical cuts?

3. Does the delay that causes phasing originate from stereo panning / effects only? Would it be true to say that there is no phasing in Mono?

:pac:

Neurojazz

The problem may be a mono delay panned left and right etc... the obvious thing would be the sound that disappers or suffers from the comb filtering - as that is the one being affected.

One test to do would be to solo that sound and then to the mono check to see if it happens... if it does then you have your culprit, then check the FX being used/panning and learn to avoid doing whatever it was that happened to cause this...

I know in cubase that you can choose a few different types of panning (i didn't know there were more than one myself!) - maybe something has gone wrong there and the stereo field is restricted... god knows... there are many things that could cause it.

The only actual time i had it was with a pad sound that had identical left and right channels (i thought i was being clever by using 2 copies of the same sound left and right) - this cause combing/phasing...

Hope that helps!

ogy

1.In order to fix the problem, is it just a matter of Eq'ing them correctly / applying a cut & leaving "the instrument" positioned where it is?
2.Or can you simply fix phasing by moving "the instrument" to +12R from +10R? and leaving the Eq as is, minus any surgical cuts?

i think both approaches are valid, but adjusting a pan position is less destructive than eqing i think. however panning changes would probably have to be a bit more dramatic then 2 degress. obviously extreme panning (R100 L100) isn't always a great idea (although it can sound good in some circumstances) but this isn't because of a risk of phasing, it just doesnt usually sound great. don't be under the impression that panning stuff out further than 10 or 20 steps is gonna cause phasing.

3. Does the delay that causes phasing originate from stereo panning / effects only? Would it be true to say that there is no phasing in Mono?

No, the most common cause of phasing is mic positioning when the initial recording happens. It doesnt matter if your in mono or stereo, some bass drum frequencies could cause phasing with bass guitar frequencies. the problem can be much worse if you multi-mic the same source as you have to make sure these mics are in phase.

a lot of stereo widening effects use anti-phase signals to give an impression of width or depth but when summed to mono these signals can cause phase cancellation.

make sure when everything is panned to the centre theres no phasing, then start moving stuff out, but as you do keep checking that your not upsetting the phase coherence.

ICN

Cheers Guys.


I think I'lll have to get hands on with it. Do a bit of looking & listening.


1.What are the correct tools / apps for the job?

2.What do you use?

3.All of these are stuck onto the Master channel?

4.Positioned before or after Master compression etc..?

PaulBrewer

Lads, while there is some sense being spoken here,there's a whole heap of Ball Ox being talked.

Before I load up my sniping rifle I'll give some posters the opportunity to 'correct' their posts ......

ICN

PaulBrewer wrote: »

Lads, while there is some sense being spoken here,there's a whole heap of Ball Ox being talked.

Before I load up my sniping rifle I'll give some posters the opportunity to 'correct' their posts ......

In the land of the blind the one eyed man is King! :pac::pac::pac:

PaulBrewer

ICN wrote: »

In the land of the blind the one eyed man is King! :pac::pac::pac:

Indeed!

PaulBrewer

He'd be turning in his grave ....

http://news.bbc.co.uk/2/hi/technology/7538152.stm

ogy

Lads, while there is some sense being spoken here,there's a whole heap of Ball Ox being talked.

Before I load up my sniping rifle I'll give some posters the opportunity to 'correct' their posts ......

snipe away mr. brewer, im in the mood for a row:)

Neurojazz

Who needs professional advice from boards members when you can use this!.

ICN

ICN wrote: »

Cheers Guys.


I think I'lll have to get hands on with it. Do a bit of looking & listening.


1.What are the correct tools / apps for the job?

2.What do you use?

3.All of these are stuck onto the Master channel?

4.Positioned before or after Master compression etc..?

The BBC are getting the hits 2day ; )

Doing this reply from the mobile. How sad? Got the landline disconnected 2day as we're moving soon.

Serious withdrawal symptoms w/out BB.

I'm probably not going 2 be able 2 look @ this 4 a while.. So thanks 4 everything Lads!

Can anyone go through / answer what i mentioned in my previous post?