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Microphone Techniques For Guitar

September 21, 2013

Often times, in our quest for the ultimate tone, we guitarists are so focused on finding the perfect guitar, amp, or pedal that we forget one of the most important parts of the signal chain - the microphone.  Whether you’re rocking a live show or recording an album in the studio, you’ll be depending on a properly placed microphone to faithfully translate your “ultimate tone” to the audience.  In this article we will focus on the “properly placed” part of this equation and cover some tried-and-true mic techniques you can use to get great guitar tones.

 

Distance & Depth

Perhaps the most crucial element of good mic technique is finding the optimum distance from the mic to the sound source. Your wall of sound will crumble quickly without an understanding of the profound affect distance has on your microphone’s bass response and clarity, as well as the sense of depth heard in the final product.

Shure SM57

Mics with directional polar patterns (cardioid or figure-8) will show a marked increase in bass response the closer they are to the sound source. The technical term for this phenomenon is “proximity effect”, and all directional microphones are subject to it in varying degrees.  A good example is the Shure SM57, easily the most common cardioid mic used on guitar cabinets. In common use the ’57 will often be shoved right up onto the grill of a speaker cabinet to maximize the proximity effect. This technique works well with the SM57 because it complements the ‘57’s natural frequency response, which exhibits a sharp bass roll-off below 150Hz and a sharp increase in mid and treble frequencies above 3000Hz.  The natural frequency curve of the Shure SM57, with added low-end from proximity effect, results in a guitar sound that exhibits both good clarity and respectable low-end.

Microphones with flatter frequency response and deeper bass, like the Sennheiser MD421, or the Royer R121 ribbon mic that we use here at the PGS studios, often need to be placed further away from the speaker to avoid the low-end mud and distortion that can result from a build up of proximity effect.  For example, we usually place our Royer figure-8 ribbon microphone 6-8 inches from the speaker of our Fender Deluxe.  In addition to achieving a more balanced overall tone, moving the mic back further from the amp also gives the sound space to “breathe” and interact with the room before it hits the microphone diaphragm, making for a lively, organic guitar tone that sounds more like what your ears hear in the room.

 

 

On or Off-Axis?

microphone off axis

Microphone off axis, photo from recordingbible.com

The most common way to mic a guitar amp is to simply aim the diaphragm of the microphone in a direct line at the center of the speaker cone.  This can often work splendidly with the right mic and guitar amp, but it can also result in harsh treble and a constipated, overly “cone-y” tonal quality.  One solution to this problem is to use what is referred to as an “off-axis” mic technique.

Off-axis means that the microphone is not aimed with the diaphragm pointed straight at the speaker cone, but angled slightly.  Directional microphones will respond quite differently when aimed off-axis, often exhibiting a high end roll-off that can be very helpful in smoothing out treble response for a warmer tone.   The slight angle can also allow more indirect room sound to come into play, which can do wonders to liven up a sterile close- mic’ed tone.

A variation on this theme is to keep the diaphragm of the microphone on-axis, but point it just off the edge of the speaker cone, rather than right in the center. The end result is similar to turning the microphone off-axis, in that it will attenuate high end somewhat, making this technique excellent for rounding off a slightly-too-aggressive distorted tone.

 

 

Multi-Mic Techniques

If you have the time and resources, using two (or more!) microphones on a single amplifier can add depth, width, and detail to your guitar sound that just isn’t possible with a single mic.  The idea with multi-mic’ing is that one microphone should capture the direct sound from the speaker, while the second microphone captures the ambient sound from further back in the room. The two signals can then be panned in various ways in the mix stage for a very realistic guitar sound that mimics the way your ears would hear the amp in the room.

Multiple Microphones

 

Image from uaudio.com

Here at the PGS studios we are constantly striving to achieve the most realistic recorded guitar tones we can in an effort to represent the gear we demo accurately. With that in mind we generally place our Royer R121 ribbon mic about 6-8 inches away from our Deluxe for our main close mic’ed sound, and a Shure KSM27 condenser mic several feet back, usually in a direct line behind the Royer.  At mix time we pan the Royer slightly off-center, with the signal from the Shure panned further left or right.

Another useful multi-mic technique is to place your second microphone at the rear of your speaker, directly in line with the mic at the front of the speaker, and then reverse the phase on one of the microphone channels.  The mic at the rear of the speaker will only pick up low end, due to the omnidirectional quality of bass frequencies, making this technique perfect for adding low-end “thud” to a small combo amp during a recording session.

When using a multi-mic setup it’s very important to be aware of possible phase cancellation issues between microphones.  This is possible whenever multiple mics are picking up the same sound source from different locations.  Symptoms to watch out for are phase-y, hollow sounds, or a very thin sound when the two mic signals are combined in the mix. If you suspect phase cancellation, simply move your distant mic slightly and check again. Often moving the microphone a few inches to one side or the other will do the trick. You might also try reversing the phase one on channel of your mixer or audio recording software.

In Summation

Hopefully this article enlightened you with regards to this crucial, oft-overlooked final element in your guitar’s signal chain.  We have covered just a few of many possible ways to mic a guitar amp, so we would encourage you to explore the subject further.  Information abounds! As with anything else, mastering these techniques requires practice and experience with your available microphones, amps, and other gear.  So get out there, throw a mic or three on your amp, and let your ears lead the way.

 

Comments

  1. Abbacus says:

    Thanks 4 da info. Very helpful stuff!

    posted on September 21, 2013 at 8:51 am
  2. jim A says:

    If you are trying to capture a clean guitar sound and find the Sm57 too harsh and the Royer too expensive, I point to the Sennheiser E609.
    Don’t just hang it by the cable.
    Put it on a stand, straight on about halfway out from the center of the speaker cone.
    Remember the sound doesn’t actually come out of the dust cap in the center or the edge of the cone. So point it where the sound comes from.

    posted on September 21, 2013 at 9:31 am
  3. Bill Harrison says:

    Also, when using two mics, don’t forget the 3:1 rule. Phase cancellation problems can be minimized by placing the second mic at least 3 times farther from the source than the first mic. Nice article, guys.

    posted on September 21, 2013 at 10:52 am
  4. Willy says:

    I’ve had pretty good results doing phase correction by recording some “test clicks” at the beginning of each take, sort of like how a clapperboard is used to sync audio/video in the film industry. In editing I can zoom waaay in to the clicks and move the tracks to make the wave forms sync up.

    posted on September 21, 2013 at 11:24 am
  5. Sudsy100 says:

    Sennheiser E906 is what I use paired with an SM57, and maybe an LDC set back a few feet.

    posted on September 21, 2013 at 4:15 pm
  6. j3kz says:

    To avoid phase cancellation, you can to record each microphones separately. Then, nudging the audio tracks by few samples, they can be aligned to compensate different distances. Advanced AudioWaves just introduced a new plug-in to align audio tracks.

    posted on September 21, 2013 at 5:34 pm
  7. Mats says:

    If the Royer is a bit too pricy, I’d recommend a SE X1R. A really nice ribbon mike for recording guitar cabs…

    posted on September 21, 2013 at 9:43 pm
  8. Lixamps says:

    This is a good article as it sometimes does not record the way you hear it in the room. Getting it close as you can to what it sounds live is the goal. Trying different mics in different locations is a good thing so that you can approximate more closely the real sound. By the way, what software and hardware do you use for your recording as this is a very important aspect of recording?

    posted on September 22, 2013 at 3:55 am
  9. Dave in Broussard says:

    I assure you, the reason I don’t sound like Andy has nothing to do with mic selection or placement.

    posted on September 22, 2013 at 11:06 am
  10. Cliff Lang says:

    The e609 is great when a “pretty” guitar sound is what you’re after- a clean undistorted electric guitar, jazz guitar, country or ballad or what-have-you. For the more typical rock sound with distortion or overdrive- a little or a lot- I’ll use a crappier mic like an SM57 or 58. The SM58 in particular has a little more midrange body than the 57 and less harshness on top.

    posted on September 23, 2013 at 5:06 am
  11. Jim A says:

    Cliff,
    I agree about the SM58 sometimes being a better choice, for the reasons you state.

    posted on September 23, 2013 at 5:11 am
  12. christian louboutin says:
    posted on September 23, 2013 at 6:08 pm
  13. micaiah flores says:

    yeah i played with mic placement while over summer to start on my first real attempt at recording my music to get known and i found some KILLER tone out of a SM58 i think… about 6-8 inches out from my excelsior combo pointed center and found MY tone that match the styles i embody.

    I.E. death cab for cutie, lovedrug, coldoplay, the delgados, nirvana, and a bit of sigur ros

    posted on September 24, 2013 at 1:18 am
  14. Ken says:

    I inherited a Shure 55 from my father-in-law’s collection. Has anyone used one of these?

    posted on September 26, 2013 at 7:49 am
  15. Cliff Lang says:

    Yes a Shure 55.. that’s a classic dynamic vocal mic. Depending on age and condition you might have something of value there, collector market wise.

    Shure still makes 55-type mics but they’re not the same as the originals. I’ve have a pair of SH55-II’s and have used one to mic my live rig many times, and I love using it for live vocals as well as well as recorded vocals. Some voices just sound good through them. The new ones are similar to an SM58, so it sounds good. Yours, I don’t know. I’d probably save it for vocals.

    posted on September 26, 2013 at 8:27 am
  16. Ken says:

    Mine is an original 55. It’s had the diaphragm replaced, or whatever the working mechanism is, and it’s in fair shape except for the mounting threads. I plugged it I to my friends PA and it sounds warm with voice input. Is there anything I need to do to protect it from being overdriven?

    posted on September 26, 2013 at 8:43 am
  17. Cliff Lang says:

    Yes Ken, keep it away from in front of my guitar amp! ;-)

    Seriously, it’s a dynamic mic so if it’s in good shape it should be able to handle high sound levels. You’ve got something there though, even if it’s not all original. I’ve seen YouTube videos where guys take them apart and restore them.
    The mounting threads… I have some adaptors that screw on a mic stand and are threaded with the same threads on top. Sounds weird but they’re pretty common since mic stands get cross-threaded a lot I guess, or banged up getting in and out of trucks, and the threads get damaged. If you got one of those and managed to thread it into the base of your mic, that would be a way to work around your damaged mounting threads. Or you might find a machine shop that would re-tap your mic’s threads, either to the original size or to match an adaptor that would screw onto the stand.
    You lucked out getting that old mic. Wish I had one! Enjoy it. They don’t make ‘em like that any more!

    posted on September 26, 2013 at 11:11 pm
  18. Ken says:

    Thanks Cliff. I’ll look into those adapters to fix the mount. I wasn’t sure about overloading the mic because a speaker is basically a mic in reverse, (I’ve seen speakers used as mics in cheap electronics), and the worst thing you can do to a speaker is over drive it. Thanks again for the help!

    posted on September 27, 2013 at 4:37 am
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    posted on December 3, 2013 at 11:56 am

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