Help! unwanted "flanger"

[Ajak]

We recorded some songs for our demo. I did the "engineering" and since I don't have a lot of experience yet I wanted to try out a couple of mics.

Right now we're doing a rough mix to record the vocals. With the first song everything went well (the recordings aren't perfect, but I understood what I did wrong).
Now while mixing the second song, we noticed that the guitar tracks have some kind of flanger on them. We checked every insert and every send and sub-groups and fx-channels and muted everything exept for the raw guitar tracks. There still was this flanger sound.

I uploaded an example of the 4 tracks mixed. Soloed every track sounds fine.
http://soundcloud.com/ajak-1/weird-guitartracks

I used 4 mics and I was very pleased with the sound of the first song. We recorded both songs in one session and I made sure no one touched the mics or the amp.

Has anyone an idea what might be the issue?

 

[mambo4]

It's not Flanging, technically it's Phasing.

Simply described, the mics are placed in different spots and angles,
so when one mic senses air pushing 'in' , another mic is sensing pushing "out".
The resulting signals, when combined, suffer from phase cancellation.

Sometimes stereo panning can fix it, but with 4 mics it could be tough.

Google "phase cancellation"

 

[Ajak]

That was my first thought as well. Indeed panning helped a bit, but it didn't disappear completely.
What I really don't understand is that the first song is okay. And I am sure the mics weren't moved during recording.

I also tried every possible combination using only 2 mics.

Is phase cancellation the only possible cause for this noise or could it also be some kind of a sample rate issue (not sure if this this makes sense at all, but we've been having problems due to sample rate settings).

Thanks anyway

 

[DuraMorte]

It's not Flanging, technically it's Phasing.

Simply described, the mics are placed in different spots and angles,
so when one mic senses air pushing 'in' , another mic is sensing pushing "out".
The resulting signals, when combined, suffer from phase cancellation.

Sometimes stereo panning can fix it, but with 4 mics it could be tough.

Google "phase cancellation"

+1
Zoom in on the waveforms, and move them so they all line up. Find a good spike in the waveform, if possible; that will make it easier to see where the inconsistency is.

Edit:

Is phase cancellation the only possible cause for this noise or could it also be some kind of a sample rate issue (not sure if this this makes sense at all, but we've been having problems due to sample rate settings).
Thanks anyway

Unlikely. Most modern DAWs auto-detect samplerate and resample if necessary.
However, it is always a possibility. I would check the waveforms first, though. They don't lie.

 

[Ajak]

Zoom in on the waveforms, and move them so they all line up. Find a good spike in the waveform, if possible; that will make it easier to see where the inconsistency is.

Thanks! That's a great idea. I'll try that tomorrow. I hate the thought of using only one mic when that combination sounds so much better.

 

[megafiddle]

To get an effect like that, the phase has to be continuously changing. The phase
cancellation from fixed position mics will alter the tone, but won't produce that effect.

With effects boxes like plangers, phasers, and chorusers, there is a low frequency
oscillator which continuously varies the phase or frequency. If you reduce the "sweep",
(the oscillator amplitude) to zero, the effect dissappears. The cancellation is still there
in that case, but it is no longer changing. It's the sweep of the frequency notches (the
cancellations) that produce the effect.

I would say something is either changing the pitch of one or more of the tracks, or one
or more tracks is being continuously delayed. If your sample rate problem was that of
some tracks being very slightly different, I think that could do it. Or something in the
processing is causing a track to be delayed later and later.

 

[seamonkey]

It happens enough that Plugin makers actually have tools to help with phase issues
http://www.waves.com/content.aspx?id=11948

But you can usually fix things by just nudging the track over a little.

A cardioid mic pointed at a speaker also pics up sound reflected from the speaker.
A cardioid itself will cancel sound coming from the rear, but it can't do this for reflected sound. Isolate sound sources and mics from each other, like walls or partitions, or roll the dice.

 

[testing1two]

You can also try flipping the polarity of one or two of the mic channels in your DAW (aka phase reverse). If you're not familiar, the polarity button looks like this:

 

[mambo4]

To get an effect like that, the phase has to be continuously changing. The phase
cancellation from fixed position mics will alter the tone, but won't produce that effect.

mega fiddle is correct, and I was wrong. You need to do some trouble shooting.

either one of your tracks is off somehow or there IS and effect operating somewhere.

To find if one of your tracks has something hinky with it, You need to bring up track 1, and bring in and out 2,3,4 one at a time and see what starts sounding odd. then repeat with track 2, 3 and 4.

To find if there is a effect operating, instead of soloing, mute 3 of the tracks. If you still hear it, then you have a must have post channel effects send operating somewhere.

 

[Ajak]

You can also try flipping the polarity of one or two of the mic channels in your DAW (aka phase reverse).QUOTE]

I tried that before but it didn't help.

either one of your tracks is off somehow or there IS and effect operating somewhere.

To find if one of your tracks has something hinky with it, You need to bring up track 1, and bring in and out 2,3,4 one at a time and see what starts sounding odd. then repeat with track 2, 3 and 4.

To find if there is a effect operating, instead of soloing, mute 3 of the tracks. If you still hear it, then you have a must have post channel effects send operating somewhere.

I did both these things as well. As soon as two tracks are playing the issue comes up.

I haven't had time yet to try moving the parts or using the plugin. I'll post when I did it.

Thanks again

 

[D1on]

If i'm reading this right you used 4 mics for 4 tracks on one amp for one guitar at one time? If so can you diagram the setup.

 

[Ajak]

If i'm reading this right you used 4 mics for 4 tracks on one amp for one guitar at one time? If so can you diagram the setup.

At the bandroom we have a Presonus StudioLive 16.4.2 digital mixer that allows us to record 16 tracks simultaneously.

Here are some pictures of the battlefield:

These mics (+ a DI which I decided not to use) -> mixer -> PC (firewire)

Does that answer your question?

Originally I wanted to use only one or two mics (just pick the best ones) but I ended up liking a mix of all four better.

By the way: I checked the first song in a pretty professional studio (of a friend) and the phase correlation was pretty high up.

 

[Ajak]

Here a screenshot of the waveforms, which are pretty much in phase. But not perfectly.

Anyway, I tried to move one track a little (two of the others muted) and it eliminated that phasing noise, but the noise didn't disappear completely before it started to sound like a delay (which makes the guitar sound not very tight...).

Would that InPhase-plugin still help me?

 

[Ajak]

I just made another screenshot of the first song guitar tracks: the lower three tracks are very well alligned, but the first one is behind the others. No phasing sound there.

Weird is, that if I move one track only 0.001 seconds there's a huge change in the sound (worse). Not sure if this helps but I found it interesting.

So I think it has to be something about the processing like Megafiddle said. What can I do about that?

These are only the raw tracks. I mixed them to a sound I like but only using the faders, no fx or eq involved. I had pretty big Cubase project that used a lot of computer capacity problems and why would that appear now?

It kind of looks like magic to me. (hallelujah, I want to study audio engineering next year)

 

[seamonkey]

The plugin has a demo, give it a try.

Also check this article out
http://www.soundonsound.com/sos/jul01/articles/micdi.asp
Which seems like what you already tried.

That gobo wall is good for isolation.
4 mics on a cab is extreme, but just pick one of the mic tracks.

You look to be well on your way to becoming a audio engineer. You're willing to spend the time and effort to get this right. That's good

 

[D1on]

Each of those Mic's has a different response curve that can be contributing to your issue. Take a look at your second screen shot and you can see the differences in the wave forms.

You're probably also getting some reflections off the wall on the right, the ceiling and what may be in front of the cab.

Like Seamonkey pic the Mic track you like the best then You might try re-recording with that Mic and a direct track to blend into the the mix.

You have the luxury to keep trying different things without paying by the hour

Record and enhance, not record and correct.

 

[Ajak]

I downloaded InPhase and tried the mono and the stereo mode. I could move the tracks in the plugin but it didn't do anything else than I did moving the tracks without the plugin. There are some other things you can do exept for delaying and since I could not find any useful tutorial I just clicked some stuff without knowing what I did to see what it's supposed to do, but that didn't get me anywhere.
For using the mono mode I'd have to use sidechaining which isn't possible in Cubase (searched the manual...).

So that didn't help me (if anyone knows how to use this plugin right, advice would be welcome). But thanks for the idea.

Per accident I noticed something else. I always just checked the beginning of the song for waveforms that were out of phase. Now I found out that somewhere in the middle of the songs the waves make a complete mess. So the tracks start more or less together and then drift apart more and more. Which led me to the conclusion that the tracks don't run with the same speed (does that make sense?).

How could that happen? That looks more and more mysterious to me.

 

[Ajak]

Hm. It's a shame. The mics sound so much better together than each on it's own...
Well it's still better than that phasing noise I guess.

But what still doesn't make sense to me is why one song has issues and the other one doesn't when they were recorded in the same session and with the very same setup.

 

[Hellbastard]

The question you should be asking yourself is, do you really need all those mics? How does each mic sound with the rest of the instruments? If you really like the sound of the mixed mics then re-record the tracks and try placing the mics in the same place or closer together, that way you won't have as many phase problems as you have placing one mic at each speaker.

 

[Ajak]

The question you should be asking yourself is, do you really need all those mics? How does each mic sound with the rest of the instruments? If you really like the sound of the mixed mics then re-record the tracks and try placing the mics in the same place or closer together, that way you won't have as many phase problems as you have placing one mic at each speaker.

I decided to use only one mic and the direct signal. It sounds quite good, but next time I'll try to place the mics closer together. To use at least two (I like the sound of the Beta 58A and of the AT2035) would be cool, so I don't have amp-plugins which just sound as great as a real amp.
Probably using less mics is also the key to a more open and transparent sound.

I thought it'd be better if I just move on, but if somebody has a possible explanation (even some kind of approaching theory (does that make sense, I'm not a native English speaking person)) for the things I told you about, I'm all ears.

Thanks for your help!