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How to mic a cab - the easy way that always works

by Mattias Girstmair, 2018.

Miking a cab can be tough. Most inexperienced people don’t really know what to listen for and end up with an unbalanced sound or a sound which doesn’t capture “the thing“ which is missing in the mix and end up reamping over and over again or use some kind of preset of an amp sim. While there is nothing wrong with using presets or amp sims you give up the chance of sounding more unique or outstanding. There is also nothing wrong with reamping over and over again but even if you learn something during the process it’s very, very time consuming.

 

So here is a very simple technique to mic a cab using only one microphone to get a good sound which doesn’t need a boatload of processing in the mix.

 

While this approach is tailored for metal and rock it doesn’t mean it can’t work for other styles of music too.

 

If you don’t mic up real cabs you can select your IRs using the same principles.

 

HERE IS WHAT YOU NEED:

- One microphone (I like using a Shure SM57 for guitar cabs and a Sennheiser MD421 for Bass cabs)

 

- A Pink noise generator (usually every DAW comes with one and if not, there are some free ones out there)

 

- Headphones with a very flat frequency response OR a frequency analyzer with a variable tilt setting (I prefer the analyzer since my headphones are open back ones and therefore they don’t isolate much)

 

- Optional: a clean power amp 

HERE IS HOW IT WORKS:

1.) Find a place in your room where you like the sound of your guitar amp.

Set all controls to noon and gain to your liking and play some riffs. Move the cab around until you are happy with the sound in the room. Every room and every position has a different impact on your sound. Bass is going to build up if you are too close to a corner and there can also be some weird reflections if the cab is facing a close wall.

 

2.) Connect your clean power amp with the cab.

If you don’t have a clean power amp turn down your master volume on your amp and set your power amp controls (depth and presence) to noon so your power amp has as little impact on the sound as possible.

 

3.) Send pink noise to your power amp.

If you are using your guitar amp send it to your FX return so you bypass the EQ section of the amp. Some guitar amps also have a direct power amp input – you can also use this input.

 

4.) Position the mic as close to the grill without touching it, pointing straight to the center of your speaker and start moving it towards the edge of your speaker.

 

5.a) Listen.

When the microphone is pointing straight to the center of the speaker you are going to hear a very high/treble noise. When the mic is moved to the edge of the speaker the high noise is getting quieter and you’ll hear a low noise starting to get louder. Move the mic to the edge and stop right before the low noise is starting to get louder than the high noise. This is where you have the most even frequency response in conjunction with your cab, mic and room.

 

5.b) Watch.

 

Put a frequency analyzer on the microphone channel in your DAW. Set the tilt on the analyzer to 3db. You’re going to see two bumps in the frequency spectrum. One in the low end and one in the high end. Move the microphone to the edge of the speaker and stop right there where both frequency bumps are peaking at the same height. This is where you have the most even frequency response in conjunction with your cab, mic and room.

Here you can see both frequency bumps. The low bump from 60Hz to 900Hz and the high bump from 1.5kHz to 6kHz. Both bumps are peaking at the same height.

6.) Start tweaking your amp to your liking and have fun recording or reamping.

 

Tips:

- Start by setting everything at noon and tweak from there.

- Play it like you mean it! If you want to sound aggressive you have to play aggressive.

- Don’t rely on high gain settings on your amp. Show your guitar who the boss is and drive your amp with your picking hand as much as possible.

USE THIS TECHNIQUE WHEN SELECTING IRS:

Put your pink noise generator first in the chain. Followed by your favorite IR-loader. The third plugin is going to be your frequency analyzer. Now switch through your IR collection while having your analyzer open and use the most even looking ones.

THE THEORIES BEHIND THIS TECHNIQUE:

Pink noise:

The pink noise, also referred to as 1/f noise, is a noise whose amplitude decreases with increasing frequency. In acoustics, pink noise is perceived as a noise in which an average person feels all frequency ranges of the audible sound spectrum and equally loud.

 

How a speaker works:

A regular speaker consists of the so-called dust cap in the center and the cone diaphragm on the side which are both producing the sound.

(have a look: https://www.researchgate.net/figure/Schematic-of-an-electrodynamic-loudspeaker_fig1_268425316)

The dust cap produces the highs and the cone diaphragm produces the lows. With this miking technique you’ll find the spot where the highs from the dust cap and the lows from the cone diaphragm are equally loud and therefore you have an even frequency response.

 

 

Since pink noise has a decreasing amplitude (3db per octave) you have to set your tilt setting on your analyzer to 3db to compensate for that otherwise it won’t look flat on the analyzer and it will give you the wrong reference.


I hope this article was helpful. Have fun recording and mixing! 


Write a comment

Comments: 3
  • #1

    Tom (Thursday, 02 May 2019 22:15)

    What if my amp only has Gain and Master, no 'depth' or 'presence'?

  • #2

    Mattias (Friday, 03 May 2019 10:48)

    Hi Tom! This shouldn't be a problem. Just follow the steps and leave out the part regarding the power amp controls.

  • #3

    Tom (Wednesday, 15 May 2019 06:48)

    Thank you!