Stereo miking and phase....

[bigwillz24]

I tried stereo miking (SM-81's) a guitar a couple of days ago using the ortf technique...

During tracking it sounded great...

After tracking and listening back from the HD24 I put the console in mono and my awesome sounding guitar track all but disappeared...

What do I do wrong?

I guess a better question would be how do you combat phase when using a stereo miking technique?

 

[mshilarious]

I tried stereo miking (SM-81's) a guitar a couple of days ago using the ortf technique...

During tracking it sounded great...

After tracking and listening back from the HD24 I put the console in mono and my awesome sounding guitar track all but disappeared...

What do I do wrong?

I guess a better question would be how do you combat phase when using a stereo miking technique?

You can't really combat it, because the phase difference is an inherent part of the stereo signal you are creating.

Once you move away from coincident stereo techniques, you lose some amount of mono compatibility. Use XY or MS if you need mono.

 

[Alexbt]

I don't know what the mic technique is, but maybe this article would be useful.

http://www.recordingproject.com/articles/article.php?article=25

 

[bigwillz24]

Errrrrrrrrr...maybe mono the tracks on the mixer while you are doing your placement?

Almost always something really simple isn't it?

 

[SouthSIDE Glen]

If you used ORTF, you most likely encountered a single-instrument version of the 3:1 rule normally quoted for multiple instruments. While the specific 3:1 distance rule may not always be the case here (it depends on the nature and size of the instrument), if you're inside the nearfield of the instrument, stereo mic placements falling in the range between coincident pairs and close spot miking can often encounter phase problems. In this case the ORTF mics places a few inches apart could indeed have phase issues with an acoustic guitar if the are placed between (very approximately) 10" and 3 feet from the guitar.

You'd have to combat that by switching to tight coincident (X/Y or M/S) or, (better yet) widening the mics to spot mic the guitar following the 3:1 rule (e.g. one body, one neck). Another alternative that also often works good on acoustic is staggered ambient miking with ome mic in a sweet spot inside the guitar's nearfield and a second one well outside the nearfield and picking up some room ambience along with the git.

HTH,

G.

 

[reshp1]

ORTF is SUPPOSE to have phase issues in mono. When played in stereo (hard panned L/R) it's the phase relationship that gives it such a realistic stereo image. ORTF simulates the slight delays between when each ear receives sounds from different directions, delays that our brain uses to decode directionality.

 

[mixsit]

... and my awesome sounding guitar track all but disappeared...

That sounds like it could be a bit more than comb filtering. Assuming the mics were equal-distant from the guit', any chance it's polarity?
Wayne

 

[EleKtriKaz]

If you like the tracks that you've already recorded with the ORTF technique and want to use those, you can use a wave editor to phase align the tracks.

You'll be able to do this in any basic recording software package. I just recently did it with some electric tracks I recorded in Pro Tools. I had a Shure Unidyne 545 III up on the grill of the cab and an AT4033 a few feet back. After phase aligning things sounded a lot better. Granted this wasn't meant as a stereo recording, just dual mono for blending the two signals.

If you have access to any program like Cubase or Pro Tools, just go in and look at both of the tracks side by side and line up the waveforms as best you can.

If you do this, you're technically getting away from the intent of ORTF micing, like someone already mentioned, but it may end up sounding better.

 

[mixsit]

If you like the tracks that you've already recorded with the ORTF technique and want to use those, you can use a wave editor to phase align the tracks.

I hope Bigwillz' comes back and talks about the mic placement factor. It'd be fun to see what else is going on here.
wayne

 

[mshilarious]

If you like the tracks that you've already recorded with the ORTF technique and want to use those, you can use a wave editor to phase align the tracks.

That's the right way to deal with your guitar tracks, but ORTF is trickier. It captures the stereo spectrum partially by creating a phase difference between left and right channels for left and right sources. So if you phase align a left source, the right source gets worse.

 

[prestomation]

It disappears in mono, so what? If you want it to be mono compatible, don't use ORTF, if you don't care about mono compatibility, then don't worry about it.

As far as phase aligning the tracks manually, that can work great as well. I record my piano using ORTF all the time, and phase aligning really can improve it. Try it out

 

[mixsit]

As far as phase aligning the tracks manually, that can work great as well. I record my piano using ORTF all the time, and phase aligning really can improve it. Try it out

Where I'm not following time alignment for this application is that if the mics are set at the same distance from the source, then would you be aligning for depth (forward/back) or for a piano example, the distance to the high strings vs distance to the low strings?
My understanding ORTF is that the intentional phase effects with the 6-7" spread are in the top octaves only, and apply foremost to arrival from the left-right axis. But whether that rules out odd results if the source is too close, or things aren't square' to the pair...?
Wayne

'Know what, let's go with a simple answer; When there are multiple arrivals, you can't actually 're-align' them. What we can do is play with the filter point combinations.
For crying out loud, cut to the frikin' chase Wayne.

 

[ds21]

If you need to keep the tracks, and nothing else works, just pick the best sounding one and only use that and fake the stereo.