The 3:1 Rule

Bil VornDick always uses the 3:1 Rule when mic’ing instruments in stereo. Here’s how it works: If your two microphones are each one unit— for example, 1'—away from the instrument, then there should be three units (3' in this example) between the two microphones. VornDick also recommends keeping the two microphones between 90 and 120 degrees of each other.

Following the 3:1 Rule ensures that your recordings will be in phase, without danger of cancellation problems later in the mixing process.

Let’s talk specifics. How do you mic up Béla Fleck’s banjo?
I use a 3:1 mic’ing technique normally on Béla [see sidebar, “The 3:1 Rule”]. As to which mics I use, it really depends on what banjo he’s playing. It depends on the timbre of the instrument. With Earl Scruggs, I’d normally used a [Neumann] KM 84 and a [Neumann] U 87. I used the KM 84 on the high side and the U 87 on the low side. That’s what he liked. But every banjo is different. If it was a very mellow banjo, then I would probably put a Milab DC-96B on the low side or a Sony ECM-33P on the low side and a KM 84 or a Miktek C5 on the high—I’m using that one a lot. But you really have to listen to the instrument first before you just stick mics up.

How important is the room that you’re recording in to the final result you get?
Very important. I have the musician move around in the room to find the spot that translates best for the overtones of the instrument. The bass is very particular to axial modes [resonances caused by sound bouncing between two parallel surfaces] in the room, where the guitar wouldn’t be as much. So if I’m going into a new room, I’ll have the musician walk around and play, sit, and then move around some more. Find where the instrument sounds like the instrument to them, then the rest of it’s easy.

Do you mic acoustic guitar the same way that you do banjo, using two microphones?
Yes, I do. Because I hear in three dimensions and you can’t get three dimensions with one mic.

Do you have go-to acoustic guitar mics?
Yeah, I have a pair of [Neumann] KM 54s that I like a lot. Then the Miktek C5s—I’m using those a lot more than the KM 84s. I used to use KM 84s all the time, but the C5, I really believe in that mic.

That’s great to hear because that mic is fairly affordable compared to the others you mentioned.
When it comes down to it, it’s the performance. You could record it on a Shure SM57, and if you’ve got the performance, that’s what the people driving down the road are going for. A lot of people use SM81s. The KSM141s, the new mics by Shure, a lot of people are using those. It depends on the budget that you have.

How far away do you place the two mics when you’re recording acoustic guitar?
They’re about 8" off. If you’re sitting with the guitar in your lap, there’s one coming in to where the curve reaches the neck; it’s not faced toward the hole. And the other one is off the player’s shoulder, the right shoulder coming down. If you look at the symmetry and the angles, they’re facing to the back of the hole on the guitar, which is where the sound comes resonating from.

You’re trying to capture the sound of the whole body of the instrument, not just getting the surface of it?

So you place the mics fairly close up?
It depends … if it’s a solo guitar, I move them back. But if it’s in an ensemble, with a bunch of people sitting around, it’s usually about 8" or so.

I use the 3:1 rule, then move the mics around with the artist playing the instrument. If you’re going to mic in stereo, put the headphones on and make sure that the left mic is left and the right mic is right and then move them around, and ask the player, “Does this sound like your guitar?”

You’d be amazed, if you move a microphone just a little bit in, a little bit to the left, a little bit to the right, what a difference that will make, depending on the overtone series of the instrument and the key that it’s in. And the instrument, of course, is going to resonate in different keys.

Do you end up panning those two microphones across the stereo field or do you bring them pretty close together?
I bring them to 9 and 3 o’clock. If you pan them all the way left and right, once it gets to a transmitter on a radio station you could have phase cancellation. I’m still old school, making records for radio. But if I were stacking a couple of guitars, I wouldn’t have them both panned that way. I’d have one at 8 o’clock and 1 o’clock and the other one at 10 o’clock and 4 o’clock.

Do you worry about bleed between the instruments when you record multiple musicians at the same time?
If you get your angles and your positioning of your microphones, and you have them pretty much out of phase with the mics on the other players, then there really isn’t that much problem if you’re in a cardioid pattern. A good example: I had Jerry Douglas, Tony Rice, and Earl Scruggs sitting within three feet of each other on one of Jerry’s recent albums, and I was able to punch some stuff in fine.

You’ve been involved with some very interesting projects for Fishman, creating the guitar images for the Aura system, and also the new Retro series guitars for Martin. The idea was that you took guitars into the studio and recorded “images” of them, which are then embedded in the guitar electronics. Were those guitars recorded in a tightly controlled room?
Yes, I had them in an environment where there was a baffle behind the guitar, so I wasn’t receiving any environment in the signal path. All you were hearing was the guitar.