How to spot phase issues in the studio!

Posted: Fri May 23, 2008 2:26 pm

I have been learning about audio engineering for many years now as a kid but what I still have never had anyone explain to me is the topic of phase issues. For instance, I was reading that there will be phase problems if you mic the top of a snare and the bottom if the mics are at a similar distance. I can see that being a problem but how can you spot phase problems? and how to you flip the phase to get rid of it?

Forgive me for I have much to learn!
Thanks for your patience! Smile

Posted: Fri May 23, 2008 2:46 pm

Does this help?

http://www.eqmag.com/article/beating-phase-issues/oct-07/31791

Kapt.Krunch

Posted: Fri May 23, 2008 3:48 pm

RobXmas wrote:

...how can you spot phase problems?

You don't really "spot" phase problems. You hear them. Any time you are using multiple microphones on a single source you have the potential for phasing issues. Not only things like 2 mics on a snare but a mic on a guitar cabinet could have phasing issues with another mic somewhere else in the room, like overheads or something like that...although it may not be as pronounced.

So then the questions becomes, "how do you know if you have a phase problem?" If you don't hear a problem outright, you need to check for it. Taking the example of a snare drum with 2 mics and assuming you are using some sort of software to record with, solo the two channels for the mics. The audio software should have a switch/button that allows you to invert the phase of the audio. Basically you flip that switch back and forth and it should sound good one way and probably not good the other way. That other way would be because the mics are out of phase and you flipping the switch puts them back in phase.

RobXmas wrote:

...how to you flip the phase to get rid of it?

As I mentioned above hopefully your software has a button to invert the phase of the channel. If you are using a console for recording it may have a button on it to invert the phase for each channel.

Other ways to handle phasing problems with multiple microphones is by moving one of the mics so that it's not out of phase. Moving it closer or farther away from the source should do the trick.

If you are recording into software and can't find or it does have a phase inverter, you can nudge the audio of one of the tracks left or right to get it into phase. To do this zoom in close and pick a particular peak of the waveforms and drag one of the tracks so that the peaks match up.

Posted: Fri May 23, 2008 3:52 pm

It really does help. So let me see if I've got this right. If you have a track in-Phase, the sound is reinforced and becomes bigger. But if it is out-of-phase, the sound cancels out because both tracks are working against eachother.

I get it! Smile

Thanks!

Posted: Fri May 23, 2008 4:04 pm

Thanks Pr0gr4m! I really appreciate it. It makes so much more sense now.

Posted: Mon May 26, 2008 3:12 pm

Another way to flip phase on the mic end, in case you have limits on mic placement, is to have a few mic cables with the two signal leads (pins 2 and 3, I think?) reverse soldered at one end. Make sure you label them as phase reversed!!!
The problem with nudging a track to align it with another when using multiple mics is that you end up with any transients (especially with a snare, for instance) being out of time alignment with one another, so you now have a slight delay between the two tracks at the transient.

Posted: Mon May 26, 2008 5:08 pm

I think an XLR to XLR adapter built as a polarity fip is a better idea

please don't confuse polarity with phase
and
slight delay can seem like a phase issue and here a bump or nudge can be the solution

desks should never have been labelled Phase Switch ON / OFF

it's not that simple

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