Double miking acoustic; placement and mix techniques

[upsidedown]

I use GarageBand to record demos, and the lightbulb went on recently that I should double mic the acoustic. For the recording process, my "method" is to point one mic (AT2035) at the bridge, the other (AT2020), spaced about 3 feet away, at the 12th fret. Works well enough and I get nice signals to work with.

When it comes to the mix, I'm winging it. I've put the "body" track at 12 o'clock, the "neck" track at 3 or 9. And I've done it the other way 'round. On their own they sound ok regardless of their final positions in the mix. But when vocals or other instruments are added, the issues (phase cancellation for one) crop up.

I'd love some suggestions - with the mix especially. But I'll admit to probably missing something obvious with the miking too!

[buzzardwhiskey]

First it needs to be said that I am not a pro, so take what I write with a grain of salt. But phase is often due to microphone distance differences. Consider making your distances similar. Or you can play with the signal alignment within your DAW (push one track back and forth in time until the phase issue goes away).

[Wyllys]

First of all, put on your headphones and listen for phase issues starting with your two mics panned hard L/R, then pan both toward the center, listening as you go.
You'll be able to hear what's best easily enough.

[Bob Womack]

I am a recording engineer. For solo guitar, I've found the spaced pair you've described (one at the body,one at the neck) to be problematic because of the vastly different frequency spectra of the two mic locations. Unless you EQ the crap out of the mics they don't any where near match, even with matched mics.

Instead, I've moved to coincident pairs or to a rather interesting system first proposed by George Massenberg back around the time he engineered the Trio album for Parton, Ronstadt, and Harris in the '90s:



This is a pair of cardioid condensers set 7" apart at an angle of 110', sort of a reversed ORTF pair. The combination of exact spacing and capsule orientation reduces phase issues just like the ORTF array does and the vertical orientation of the array eliminates the mismatched spectra problem. I aim the array at the fingerboard near the body joint and start at a distance of 12-14" in a good room and move in or out from there as needed. To those who are discombobulated by the vertical alignment I say two things:
1. Try it and listen to the results.
2. Remember that the mic has no idea of its spacial orientation, only of the sound waves presented to it.

It's done well for me on dozens of sessions.

I hope that helps a wee bit for you.

Bob

[Wyllys]

I also work as a recording/live broadcast person. There are many "array" techniques to try, but in the beginning there is a cardinal rule regarding mic placement and phase anomaly/comb filtering issues...the 3:1 rule.

http://en.wikiaudio.org/3:1_rule

It's good to know how, better to know how and why. Here's a link with nice pics of common set-ups. I'm a fan of Blumlein if the room is good.

https://www.cakewalk.com/Support/Kno...coustic-Guitar

[rick-slo]

The principle behind the 3:1 rule regards multiple mic'ing of multiple sound sources, not multiple mic'ing of a single sound source. Regarding this thread Bob has good reasoning given about coincident mic'ing, though if the guitar is just part of a mix of instruments and is not the main focus of the recording then a single mike recording of the guitar would probably be just fine.

[Doug Young]

Originally Posted by upsidedown

I use GarageBand to record demos, and the lightbulb went on recently that I should double mic the acoustic. For the recording process, my "method" is to point one mic (AT2035) at the bridge, the other (AT2020), spaced about 3 feet away, at the 12th fret. Works well enough and I get nice signals to work with.

When it comes to the mix, I'm winging it. I've put the "body" track at 12 o'clock, the "neck" track at 3 or 9. And I've done it the other way 'round. On their own they sound ok regardless of their final positions in the mix. But when vocals or other instruments are added, the issues (phase cancellation for one) crop up.

I'd love some suggestions - with the mix especially. But I'll admit to probably missing something obvious with the miking too!

When doing spaced pairs, the intent is usually to keep them separated, panned hard left and right - spaced mics inherently have phase differences, it's part of why that mic setup sounds the way it does. It's only an issue when you pan them together, so the solution is to not do that. Keep them panned hard right and left. If the sound is too wide for you, change the mic positioning until you get a sound you like. As Rick and others have said, if you're mixing other instruments or voice, maybe you don't even want stereo guitar - try a single mic. Or try a coincident setup like X/Y or Bob's vertical near-XY. You'd still want to keep the tracks panned hard left and right in most cases with those mics setups. So in short, my suggestion is to use mic placement to dial in the sound you want, not panning.

But, a question. You say phase cancellation occurs when adding other instruments. Are you overdubbing? Or singing into yet another mic at the same time?

[KevWind]

Originally Posted by Doug Young

When doing spaced pairs, the intent is usually to keep them separated, panned hard left and right - spaced mics inherently have phase differences, it's part of why that mic setup sounds the way it does. It's only an issue when you pan them together, so the solution is to not do that. Keep them panned hard right and left. If the sound is too wide for you, change the mic positioning until you get a sound you like. As Rick and others have said, if you're mixing other instruments or voice, maybe you don't even want stereo guitar - try a single mic. Or try a coincident setup like X/Y or Bob's vertical near-XY. You'd still want to keep the tracks panned hard left and right in most cases with those mics setups. So in short, my suggestion is to use mic placement to dial in the sound you want, not panning.

But, a question. You say phase cancellation occurs when adding other instruments. Are you overdubbing? Or singing into yet another mic at the same time?

Agree with everything above.

I also questioned the phase issue springing up when adding additional tracks ? If the recording of guitar has phase issues they would be present with just the guitar tracks playing. Thus it would seem what is happening when listening to additional tracks might be something other than phase related.

[upsidedown]

For the sake of clarification I should start by saying that what I'm usually getting is a less than optimal mix. As in, "nice, but could be better." Phase cancellation may be a part of that, and it no doubt is. But dropping that term may have taken the conversation down a too specific path.

Doug, thanks for the suggestion to pan hard L/R (when using the mic spacing I described). To answer your follow up, I am overdubbing. Usually a second acoustic guitar and almost always vocals. The use of the second acoustic leads to the next question; if I'm panning the first guitar hard L/R, where do I put the second? And do my mix options change if I employ a different mic placement, similar to the one suggested by Bob?

As mentioned, I'm using 2 AT large diaphram mics, so I'd probably go with the Blumlein technique that Wyllys recommended. I'm sure that will lead to a whole host of new questions for y'all.

Thanks for all of the replies. They're very much appreciated.

[rick-slo]

Originally Posted by upsidedown

For the sake of clarification I should start by saying that what I'm usually getting is a less than optimal mix. As in, "nice, but could be better." Phase cancellation may be a part of that, and it no doubt is. But dropping that term may have taken the conversation down a too specific path.

Doug, thanks for the suggestion to pan hard L/R (when using the mic spacing I described). To answer your follow up, I am overdubbing. Usually a second acoustic guitar and almost always vocals. The use of the second acoustic leads to the next question; if I'm panning the first guitar hard L/R, where do I put the second? And do my mix options change if I employ a different mic placement, similar to the one suggested by Bob?

As mentioned, I'm using 2 AT large diaphram mics, so I'd probably go with the Blumlein technique that Wyllys recommended. I'm sure that will lead to a whole host of new questions for y'all.

Thanks for all of the replies. They're very much appreciated.

Record mono and less issues about panning left or right - somewhat similar reduction of issues but to less of a degree with coincident stereo mic'ing. Probably pan one guitar a little right and the other a little left if both guitars prominently featured in the recording.

[upsidedown]

Originally Posted by rick-slo

Record mono and less issues about panning left or right - somewhat similar reduction of issues but to less of a degree with coincident stereo mic'ing. Probably pan one guitar a little right and the other a little left if both guitars prominently featured in the recording.

I do record in mono. Thanks Rick.

[rick-slo]

Originally Posted by upsidedown

I do record in mono. Thanks Rick.

Then things are simplified, and don't double mike.

[Bob Womack]

Originally Posted by upsidedown

And do my mix options change if I employ a different mic placement, similar to the one suggested by Bob?

Here's the deal with near-coincident and co-incident mic placements: When the two mics are recorded onto two separate tracks and those tracks are panned outboard in the mix, you should have a strong center image and some outboard interest in a stereo mix. Co-incident systems typically feature a strong center image but often don't have much outboard stereo interest. That is why many utilize near-coincident systems like the one I mentioned. Those systems are designed to protect the phase relationship of the stereo pair and thus provide a strong center image while providing more interest to the outboard portion of the sound field than a coincident pair can. If you find that the center image isn't as strong as you desire, you can pan the two channels back inboard by equal amounts, a little at a time, until you firm up the center to taste.

If you are recording mono it doesn't make a whole lot of sense to use two mics and introduce the possibility of phase issues. However, recording mono doesn't make much sense in the current market where everyone is used to stereo. My opinion.

Bob

[Doug Young]

Originally Posted by upsidedown

Doug, thanks for the suggestion to pan hard L/R (when using the mic spacing I described). To answer your follow up, I am overdubbing. Usually a second acoustic guitar and almost always vocals. The use of the second acoustic leads to the next question; if I'm panning the first guitar hard L/R, where do I put the second? And do my mix options change if I employ a different mic placement, similar to the one suggested by Bob?

I'm not really following, especially with your comment elsewhere that you're recording in mono. All these mic techniques - spaced pairs, XY, Bob's vertical setup are stereo techniques. If you don't need stereo, then just record mono. You basically (almost) never want to blend 2 mics to mono.

It seems you are recording multiple guitars and vocals? You could still record in stereo - I've done tracks where I recorded even multiple guitars in stereo, and either left them that way, or slightly shifted each to one side (not collapsing the stereo image - I record stereo tracks in Logic (not dual mono tracks) so that the "pan" control is really just lowering the level of one track, not panning them inward as you describe). But for the most part as soon as you are mixing multiple instruments, you are likely to just want mono. It's an artistic choice - maybe you want one guitar to be in stereo to create a big spread, and the others in mono, so you can place them anywhere. Could work. But this wouldn't be a very realistic sound. The starting point for many multi-instrument mixes is to create a "sound stage", so the listener hears something similar to what they might hear in a live performance, violins on the left, cellos on the right in an orchestra, for example. Or 2 guitars, mostly left and right with a singer in the middle for example. In that kind of approach, every single sound is mono, and you create a stereo sound by where you place each source.

[upsidedown]

Originally Posted by rick-slo

Then things are simplified, and don't double mike.

I like to double mic. I think it adds a dimension to the sound.

Since updating to GarageBand 10, I haven't been able to find the button for recording a track in stereo anyway. Too bad; especially seeing as how all the advice you guys have been giving me deals with stereo!

But I have been recording in mono and as Doug said, creating a stereo effect with pan and volume on the multiple tracks.