Sunday, April 8, 2012

HOW TO MIC A GUITAR AMP (a guide for dummies)

Hello and welcome to this week's article! Today we're going to talk about how to get a good tone miking a guitar amplifier.
First off let's say that miking a guitar amp is not particularly difficult, but it should be done on an acoustically treated room, otherwise, if you want to microphone an amplifier, especially a tube amp which needs to be pushed at a high volume in order to achieve that "roaring" sound, your room will be crowded with reverbs, and the final result will be a "live on a cathedral" type of sound.

Let's now talk about microphones: you can use dynamic microphones or condenser ones, which are more sensitive, delicate and faithful in terms of higher and lower frequencies, more suggested for acoustic guitars, clean electric guitars or low wattage amps;
my suggestion is, if you want to use just one microphone, to use a dynamic one, which is able to handle higher pressure levels, so it's better suited for rock and metal guitars, but if you want you can also use both dynamic and condenser in order to achieve a more harmonically rich tone (of course anyway you could experiment by using as many microphones as you want: rumor knows that Metallica used 9 or 10 mics to get the "...And Justice for All" guitar tone, and if you find that you don't need one, you can just delete it later on your Daw).
Two dynamic microphones which are the industry standard for both live and studio sound are the Shure SM57, which features a very strong eq curve made to cut throuhg every mix, and the Sennheiser E906, which under many points of view is the Sennheiser version of the Sm57.
Those two microphones represent the two standard ways of microphoning: the Shure SM57 and similiar microphones are directional ones, which means that they take the sound they're pointing at, while the Sennheiser E906 is of the "Lollipop" kind, which means they're flat and can be hung on the cab directly by the cable, so they eliminate the need for a mic stand.

How to get the right tone? The idea is to use your ear instead of the microphone, getting close with your ear to the speaker (use earplugs if needed) and moving your head as if you would place a microphone, while you, or someone else, play the guitar: that is the sound that is going to be grabbed by the microphone, so move the equalization and gain control of the amp accordingly, keeping in mind that on record usually is needed LESS gain and more mids than you think to obtain even the heaviest tones, preserving attack and clarity.
The optimal situation would be to hear the sound from a pair of monitors or headphones from an isolated room, so that you can hear exclusively what is going into the DAW. From there you can ask to the guy next to the cabinet to move the microphone closer or farther from the center of the cone, until you find the "sweet spot".

How to place the microphones? For a "Lollipop" style microphone, just hang it from the top of the cab, towards the center of the speaker. the more you move it off the center, the less treble it will catch, and the more the sound will be oriented towards the mid-lows. Find the "sweet spot" and you're done :)

For Directional microphones, instead, things gets a little bit trickier, since you can also decide the distance from the speaker, and wether to keep them on axis on the speaker or to put them off-axis, and of which amount. Here is some example of what you may obtain:

- On axis, 2,5 to 5 cm of distance, center of the dustcap: maximum presence, attack and high frequencies.
- On axis, 2,5 to 5 cm of distance, at the edge from the dustcap and the cone: a bit less attack and more bass.
- On axis, 2,5 to 5 cm of distance, halfway between the center and the edge of the speaker: a more balanced sound, compromise between attack and low-end.
- Off axis, 2,5 to 5 cm of distance, 22° or even 45° towards the dustcap: a mix between the sound you would get going on axis towards a point between the center and the border of the speaker, and the one you would get pointing at the dustcap.
- On axis, 15 to 30cm from the speaker, center of the speaker: Medium Attack, fuller sound.
- On axis, 60 to 90cm from the speaker, center of the speaker: Softer Attack, reduced low frequencies.

Move the microphone closer or farther the dustcap until you find the sweet spot that allows you to get a tone that holds all the tonal characteristics that you need!

Additional Awesomeness: you can also use a combination of two dynamic microphones: one pointing towards the speaker using one of the techniques listed above, the other pointing THE BACK of the cabinet. So now you'll have two tracks of the same sound, and if you listen them in mono (or check them with a SPECTRUM ANALIZER) you'll surely notice some phase problem: some frequency of one track will cancel some other frequency of the other. Try flipping the phase of the track recorded to the back of the cab, and choose the one that cancels less frequencies, this technique, although may need some practice to be mastered, may help you thickening your tone!

A very common microphonig technique for distorted guitars with two dynamic microphones consists into using a Shure Sm57 to catch the mid frequencies from the cone, and a Sennheiser MD421 for lowest and highest frequencies, this combination creates a very complete and usable spectrum (see picture on top).

A good technique for clean or slighly overdriven guitars instead, is to use a Shure Sm57 and a condenser microphone (a Neumann TLM for Vocals, on this example picture below): set the Shure close to the grill until you can capture the bulk of the midrange, then set condenser 10 to 20cm away from the cabinet, in a position that will allow you to catch that extra low end, the warmth and the harmonic richness of the tubes to make the sound really pleasant and "tri-dimensional".

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