Multiple Microphones on Guitar Cabinets

For those who still insist on sticking mics in front of guitar cabinets, here’s an old one I wrote for recordingproject.com

Introduction

A lot of this came from following around the God of Metal Engineering: Bill Metoyer. (Check the back of your records; if you don’t see his name on anything, you need a trip to the record store). I am sharing this because I see many posts on many online forums concerning recording guitars with multiple microphones. It is my hope that this tutorial will serve you well. Follow all that is suggested, and be on your way to glorious guitar tones whenever, and whatever you record with. Multiple mic’s on guitars doesn’t have to produce horrible phase artifacts if approached right. Here we go!

Intonation

Make sure your guitar is in tune, and intonated properly. Different intonations, even slightly different, can make completely separate flavors of distortion so get it as close as you can. If you know the difference in distortion sound between a 24 3/4″ scale guitar neck and a 25 1/2″ one then you know what I’m saying. In addition, guitars and basses that are not intonated together will surely fight each other in the mix, causing one or the other to dominate, and never blend perfectly. If you are not skilled in intonating your guitar, it is best to take it into a luthier that is reputable!

Preamp Gain

Most of the best guitar tones, especially in “metal” genres, come from less, a whole lot less (that’s right LESS), distortion/preamp gain than you would use live. For riffs and chord changes, the real heaviness comes from dynamics – the fact that it gets louder when your pick hits the string than when the string is just resonating.

This seems obvious, but it’s not really. You need to maximize the dynamic range at this stage because from here on out, the signal is going to be compressed and degraded in all sorts of ways. In most cases the gain should be about where a chord actually comes out clean when you strum softly. Transistor amps/pedals may not do this (some will), which is another reason tubes are usually preferred for this type of thing. Not all preamps are created equal! Having a preamp that works with your genre is essential! Pick wisely, and pick from a lot of experimentation. Keep in mind too that pickup/preamp combinations work differently from each other. A Seymour Duncan Invader pickup will drive just about any preamp to distortion a lot quicker than a stock Fender Strat single coil pickup will. So much more could be said about selecting the right pickup and preamp for your “sound”, but that would regress this tutorial. Therefore, we move on!

Tone

Scooped mids, cranked bass and treble right? WRONG!!! For recording you will need a lot more mids than you normally would live. You need to be heard. The way our ears work, we take most of our cues from the midrange. Get as much body in the tone as you can…. not bottom, body. You can always scoop it out later if you must. As the carpenter says, “Always cut long.” Again, we could talk a long time about the tonal characteristics of different amps, but that would regress this tutorial.

Power Amp and Speaker

Ok, on to the power amp or the power section of your head if you use one. Here is where you start the dynamic reduction process. You want to get a sound with enough sustain to work, but, being careful whether or not you want to actually hear power tube saturation or speaker distortion. Nothing right or wrong here, you are only limited to what sound is right for your production. Get a good sound that you enjoy – that is what counts.

Make sure (if you can at this point in the recording) that the sound fits with the other tracks. You will probably use a speaker that you wouldn’t like live for this process. A speaker with more mids than normal, like a Celestion Vintage 30, or maybe a Kendrick. Greenbacks are good live, but sometimes lose that all-important midrange on tape. Watch the speaker distortion! Get a power level that makes comfortable dynamics for you, maybe on the less compressed side so you gotta work just a wee bit harder than normal to crunch it up.

Initial Mic Placement

Now, stand in the room with the amp. Get your head moving around until you find the one speaker that sounds better than the others, or maybe just a real good spot where it seems to sound best. I am assuming we are not going after a “room” sound at this point. Stick a 57 right there, where your ear was.

Now, at the console, first verify that this is roughly the sound you heard out there. Be sure levels are where they should be etc… No EQ at this point on the console. Have someone move the mic back towards or away from the cab (or do it yourself with headphones). You are doing two things with this:

1) Changing the ratio of direct (from the speaker) vs. reflected (yeah you might be only a few inches from the cab but the room still is playing a huge part) sound coming into the mic.

2) Changing the amount of dynamic compression that the actual volume of the speaker is causing in the mic’s diaphragm, ribbon or voice coil. You are changing the behavior of the sound here.

Once you like the placement of your mic, its time to get very tricky.

The Second Mic: Dealing with Phase

One mic is almost never enough, but with two or more, phase cancellation rears its ugly head. Nevertheless, we got a trick for that right?

Here it comes.

Put the guitar down. Make it make noise, or take the cable off and stick it on something that will make noise. This noise has to be stable and constant…. a fender strat’s hum is perfect for this assuming it has some midrange harmonics to it.

Using your console’s meters, bring that noise up to wherever your “zero” is. This will probably require a lot of mic pre gain so make sure your speakers are turned down. Don’t let anyone touch the guitar or whatever the noise source is. Once you’ve got the signal to zero, mute the channel.

Next go into the room with the amp, and put your second mic about equidistant from the speaker as the first mic … Be careful not to disturb Mic#1.

Back in the control room, bring Mic#2 up to zero.

Now, very importantly, pull Mic#2’s fader (NOT mic pre) down to -infinity. Unmute Mic#1. Slowly push Mic#2’s fader up towards zero.

If the volume at your final Left Right Mix buss on your console goes up, you need to flip the phase of Mic#2. If your console doesn’t have a phase switch, make an out of phase cable. Just reverse pins 2 and 3 on an XLR, and make sure you label that cable so later on you don’t screw up some overheads or something. Remember: if the volume goes up, flip the phase.

If the volume goes down, we can proceed… keep flipping the phase until the volume goes down when they are at their zeros.

Now pick up a bat, knife or gun. Whatever you are best with. Threaten anyone in the control room with it and say, “DO NOT touch that guitar! I am going to have headphones on at extreme gain levels and am risking it all so you can have a good guitar sound.” Wave the weapon around menacingly until you are sure that they get the point. Kick them out and lock the door if you can’t trust em… now is not the time for gags.

Go out to the amp with headphones on. You will hear a hiss or buzz or hum… make sure the hum in the phones is louder than the one you can hear directly from the amp.

Do not cough; you will blow your eardrums right into each other. Be careful of any noise that may be present.

Now, extremely carefully, move Mic#2 back and forth, left and right. Slowly. You should hear a whoosh sound, much like a flanger pedal would make.

The trick here is to find the spot where the least amount noise is coming out of the headphones. Keep moving the mic until you find it.

Have you caught the theory yet? We are looking for the spot where the two mics are the most in phase with each other. If one is phase flipped, then at the most in phase spot, they will nearly cancel each other out. Find that spot! Once you get it, take off the phones and go back to the console.

Turn both mic preamp gains all the way down. Put fader one at the unity position on your console. Play your guitar and turn up the mic pre gain until you hit zero. Now mute Mic#1. Now turn fader two to the unity position. Bring up mic pre #2 until you hit zero.

Unflip the phase on Mic#2 at this point so that both mics are in phase.

Unmute Mic#1 and mess with the faders. Those two faders now become the best EQ money can buy! Turn up one, then the other, experiment to your heart’s content. Once you get a sound you like, buss them together and send em to a track… or keep them separate if you want some choices later.

Revel in your glorious new tone!

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