Advanced Guitar Mic'ing and Mixing

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Another long guide on the art of mic'ing a guitar cab with 2 different microphones to achieve a fuller sound. Also includes tips for use on mixdown to get that "pro" sound.

Electric Guitar Mic'ing.

Technical Skill Level: 3 / 5

Foreword:

There are two fields of thought on Mic usage when mic'ing guitar cabinets / amps. Using a Dynamic mic like a Shure SM-57 gives a very "gritty" sound, but often lacks top end sparkle that makes the sound cut through in a mix meaning you have to apply lots of EQ and / or reverb to get a usable sound. Using a Condenser mic will often give a more detailed sound with more "fizz", but often lacks lower-frequency response and as a result can sound too "thin" and "transparent".

In this tutorial I will outline the setup and procedures for combining these two mic's to enjoy the benefits of both, allowing you to achieve a "richer" electric guitar sound from your home studio setup. I will also be covering some basics on treatment and practices to employ to push that sound even further upon mixdown.

Equipment used:

Guitar Amp - The amp you use is pretty much down to what you have - bear in mind that the bigger the amp, the "phatter" the end sound (in most cases). Also, bear in mind that it is best to drive the amp pretty hard when recording the sound, as the desirable distortion elements will not kick in at low volumes (especially when mic'ing Tube (Valve) Amps. As a result, it is sometimes more desirable to crank up a small amp and record that, rather than using a large amp, but having to run it at lower "power levels" due to neighbors, or the wife :) If you have a range of practice and "stage" amps, try them out, find the one which one sounds best at the volume levels you can operate at.

Dynamic Mic - In this tutorial I will be using a Shure SM-58 - ideally an SM-57 is more desirable (but I don't have one! :), however nearly any dynamic mic will do the role sufficiently. Dynamic mics can take very extreme SPL's (Sound Pressure Levels) and as a result, you can shove them right next to the cone to really pick up the "roar" of the amp. Dynamic mics, due to their build design, also have a tendency to have a slower "transient response" - I won't go into detail here, but this is again very desirable to close mic'ing a cab.

Condenser Mic - In this tutorial I will be using a Rode NT-1 (or NT1A), however any LARGE DIAPHRAGM condenser mic will be sufficient (note that you should use a large diaphragm mic, a small diaphragm mic will not capture the same tonality - feel free to experiment, by all means, but that's not how I work :) Condenser mic's are quite a bit more delicate than dynamic mic's, as a result you shouldn't shove one of these right next to the cone, the high SPL's could possibly damage the mic - keep it at least 4 inches away and you should be fine. Condenser mics will usually have a very good "transient response" leading to a very dynamic and "open" sound.

Pre Amps / Mixing Console - In this tutorial I will be using 2 mics, one of which (The NT-1) requires Phantom Powering. I personally use my Behringer MX3282a, however any desk should do the job nicely (Even the MX802 is capable for this task). If you have the option of using a high quality channel strip (like a Joe Meek VC3Q for example) then use it to feed the Condenser Mic in this setup and you can use the compression settings to you advantage when tracking.

Recording Medium - Most of you will be recording onto computer, I will leave how to hook everything up and getting your software running smoothly until another tutorial.

Method:

Wherever possible, set the guitar amp up in a separate room to your studio / control room. If you have a vocal booth, nearby spare bedroom or even a cupboard, use that. Set up the amp as usual, dial in your preferred settings and have a quick jam to check that everything is working ok and sounding the way you like it. Remember that if you are using a Tube Amp you need to let it "warm up" for at least an hour before you start recording or the tonality of the sound may change as the valves change in temperature.

Start off by positioning the condenser mic. Using a stand set it up about 12-15 inches away from the speaker and so that the capsule is facing towards one of the cones. If your cab has 2 or more cones then concentrate on just one cone, try not to place the mic's in between the cones as the sound will nearly always be weaker.

Now you need to plug the Condenser Mic into a channel on your Mixer / Preamp. Ensure that the Phantom power on your Mixing desk / preamp is turned Off, this is important, plugging an XLR lead into a Condenser mic when the Phantom Power is on can easily damage the Microphone. Once it is plugged in at both ends (Mic and Channel Strip), then turn on the Phantom Power, wait about 10 seconds for it to level out. Bring the channel fader up to Unity (0dB) and set all the EQ's flat. Start off with the gain all the way down. Get a friend, your sessionist or anyone else to play the guitar while you adjust the gain trim - make sure that the signal does not peak and averages around 0dB on the mixer (Note, we are only dealing with the MIXER here, not the recording medium yet!).

Now we need to setup a "headphone mix". Plug a pair of headphones into the "headphone" out of your mixer / preamp. You should now be able to hear the guitar in your headphones via the Condenser mic - so far so good :)

Turn up the headphone volume nice and loud and venture back into the room where the Guitar Amp is setup. You need the headphones nice and loud so that you hear the sound that the mic is picking up rather than the sound of the actual cab. Now position the Condenser mic so that it is in the sweet-spot. Spend a good few minutes moving the mic around slightly until you are confident it is picking up the best possible sound - it should sound "airy" and "open" - don't worry that it does have much "grit" about it, we will address that in a minute :).

Once you are happy with the positioning, go back into your control room. Make sure you shut all the doors between the two locations and use pillows / towels / duvets / quilts / family pets to block any gaps where sound is leaking through. Now listen to the sound of the cab back through on your studio monitors - if you are happy with the sound, you are ready to move onto the next mic - if not, put the headphones back on and venture back into the "live room" to reposition the mic again.

When you have got the sound you are after with the one condenser mic, you are ready to place the dynamic mic (SM-58 in my case) to add more "depth" and "grit" to the sound. When placing the Dynamic mic ensure that you don't knock the Condenser mic accidentally as you will then have to reposition it to get an optimal sound. Get the dynamic mic right up next to the grill, I place mine about 2inches away slightly off axis pointing towards the centre of the speaker - These close mic'ing techniques are already covered in another tutorial available here at Home Recording Central.

Now that the mic is in position it is time to head back into the control room. Turn the fader all the way down to -Inf on the Condensers's channel and turn the Dynamic's channel up to Unity - as before, make sure the EQ is set to flat and then slowly adjust the gain until you get a strong signal that fluctuates around 0dB. The dynamic mic should sound pretty good by itself - we're done! both mic's are in place and we are ready to record?

Nah, that's far too easy...

Here comes the real catch of using two or more mics on a single sound source - our good friend "phasing" - this bit is FUN!

From here on the Condenser Mic (Rode NT-1) will be running on Channel 1 and the Dynamic Mic (Sure SM-58) on channel 2; just for the sake of simplicity.

Set channel 2's fader to -Inf dB so that you are now not hearing any sound from either of the mics. Bring up channel 1's fader to Unity again and you will now only be getting the sound from the condenser Mic, now, bring up channel 2's fader ... whats happening ... the sounds getting thinner?! Yep - that'll be the phasing.

Phasing occurs because the Mics are receiving two different "waveforms" (like you see on the computer screen in your Sample editing program) - Because the mic's are recording from the same source (the guitar amp) and are very close together, these waveforms will cancel each other out when they are mixed together resulting in a very thin sound as opposed to what the two mics would sound like if they were "in-phase" (which would be "phatter" than just the one mic).

Obviously this is not a good guitar sound, what the hell are you going on about jues, you made me read all this way and you have created a crap guitar sound. Hold on, this bit's a touch fiddily, but you'll be pleasantly supprised when we get it right :)

Have both channels set to unity and both panned centrally - pop on the headphones again and go back into the "live room". Do not adjust the position of the Condenser Mic, that is find where it is, the easiest one to adjust is the dynamic mic (the SM-58), pick it up and move it about very slowly while someone else is playing the guitar - as you move the position of the mic, so the phasing will shift - it will sound a bit like a jet plane going overhead and sounds a bit wierd - eventually you will find the meeting point of the waveforms and as if by magic the signals will go "in phase" - go back into your control room and check it on the monitor speakers - you will know when you get it because the sound will no longer sound thin and lifeless, but all phat and creamy. If you have a very willing friend, it's preferable to send them into the control room to move the Dynamic Mic around while you listen on the speakers. Shout at him to stop when he finally gets it in the right position and the two signals go "in-phase".

Once you have got the two mics "in-phase" you must do your best not to move them - very slight movements shouldn't be a major problem - but large knocks will almost certainly move them enough to put the signals out of phase again - in which case you will need to go back and readjust the positioning (and hit the person who just knocked the mic's :)

Right, so we have a phat, in-phase guitar sound coming though into the mics - excellent, we are now ready to track this sound onto your recording medium (in my case, I use Cubase SX). Ideally we want to record both mics separately so that we can apply different EQ, compression, reverb, delay, and volume settings to each one if we need to. As we are only using two channels, you need not worry about using AUX sends or groups - just pan Channel 1 hard left and Channel 2 hard right - you will now have one mic coming out of each of the two speakers and with a it of luck into the respective Left and Right inputs on your computer.

And away you go, play along to the track, monitoring on your studio speakers - remember not to monitor too loud or it may bleed across from the control room into the live room - if you are getting a bit of "bleed" then you need to use more pillows, etc to block any gaps that the sound is travelling though, or just turn it down in the control room a bit. When you have finished your take you will have two separate recordings - one for each mic.

Hurrah - we're done, you can now pan these signals central on the computer and adjust the level of them and apply a bit of EQ to get the sound you are after. As far as the levels go I will start with the condenser mic up at unity and then mix in the dynamic mic signal until it adds the required amount of "grind" to the sound...

"Okay, this sounds pretty phat - but it's not PHAT! C'mon, you promised PHAT guitar sound!" :)

Okay, here are my tips to using that mic setup to achieve a REALLY phat sound - but these are my tips - so be careful who you give them out to :D

First up is the good old time honoured classic of double tracking. I double track every single guitar part that I record. This very simply involves playing the part as per usual and then going back and recording it again (make sure that you solo the first performance, as it may put you off if you listen back to it when you record the second). Then just pan the first take hard left and the second take hard right. Obviously your playing needs to be pretty tight for this to work, but as long as you (or your sessionist) is fairly competent it will work great - this technique along will improve the phatness of the sound by a great amount. There is also a trick whereby you flip the phase of one of the takes, thus putting it out of phase with the other - this creates a psycho-acoustic illusion whereby there seems to be a very large "hole" in the middle of the stereo field, you'll find that vocals, bass and drums fit beautifully in this gap - tho it is entirely up to you as to whether you like this sound or not.

Next up is the use of compression. I'm not going to give a detailed explanation of compression here, there are plenty of articles available on that subject alone. The things to bear in mind is that you are after a really "crunchy" feel when compressing electric guitar (especially the distorted parts).

Set the ratio to about 4:1 and have the attack around 18-25ms and the release to about 20-30ms. Now lower the threshold slowly - get it to just the right spot and the sound will become a damn sight crunchier, push it too far and it will become too "flat" and "smooth" sounding - this maybe what you are after, but I'm personally not :) Clean guitar sounds can sometimes benefit from a slightly longer release to exaggerate the playing - experiment with the attack and release to get the sound you are after.

Because we used two mics we have the option of either compressing them individually or compressing the combined result - I personally go for the latter option (by placing the compressor on a bus and bussing the two signals to that), but you can easily experiment with different settings for the dynamic and condenser mics. Bear in mind that the dynamic mic is meant to add "grit" and so leans to the side of "over-compression" where as the condenser mic is used to capture the "air" and "fizz" and so probably wants a bit less - however, let your ears be the judge.

I personally wouldn't even touch EQ until you are doing the final mix of the tune when all the instruments are in place - go easy on the EQ, don't use too much and try to cut rather than boost - you may want to apply a Low Pass Cut under 120Hz to make a bit of room for the bass guitar if it's betting a bit lost - also, cutting at around 800Hz can give a bit more "thrash" to the sound.

Go _very_ easy on reverb on the Distorted sound. If you really want to use a bit of 'verb, then choose either a plate program or a small room program and send only a small amount - if you can hear the reverb then you have probably applied a bit too much - too much reverb will only muddy the mix, stealing frequencies away from the other instruments resulting in your mix sounding a mess. Clean guitar is a different story - clean guitar will sound much warmer with a bit of plate, room, or even chamber reverb on it - make sure the decay times are not set too high unless the piece is very laid back - stay under about 2 seconds, and again, don't send too much or it will sound messy and amateur.

Tap delays can also sound really good on clean guitar (not distortion!), use small taps (start with one at around 40-75 depending on the tempo of the track) (remember BPM x 0.6 = Time in Milliseconds) - you can add up to two or three taps before things start getting a bit messy, if you plugin (or outboard) has filters built in, use them to good effect to "filter away" the later taps - if you also offset the taps in the stereo field it can sound VERY pleasing.

As a last pointer, I will recommend that it is a good idea to do a track in "sections" - if there are both clean and distorted parts in the song, then do a first take and get all the distortion parts down, then go back and do another take and get all the clean parts down on a separate track (as in Lane) - this way you will avoid any timing issues or noises created by pressing pedals / stomp boxes - it also makes it easier to apply effects only to certain sections of the song.

Well, guess I've waffled enough - enjoy, and let me know how you get on.

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User-submitted comments

LocoG
Feb 25, 2003 07:16 am
simple compressor question
How important is it to compress guitar before recording, rather than after? As you might have guessed, I dont own an outboard compressor. Im using Cubase vst. Is there any way to use the software to compress in real time? Anyway, thanks for the great article, I think the phasing info is really going to help me out.

Jues Replies:
Getting a good compression sound on the "way in" (eg: whilst the signal is still in the analouge domain) is very important in regards to achieving a "pro" sound. For the best results you will want a "tube" compressor - or at least one that models tube warming effects.

Unfortunatly there is no way to create this type of compression "on the way in" using a software plugin. However, these plugins are VERY usefull for adding extra "post" compression to give the sound even more crunch once it is in the digital realm.

brock
Jun 23, 2003 05:20 am
very good
very good explaination. i'm sure this will help alot of people out since this seems to be the biggest thing that people search for when they odn't know how to record and there trying to get a bigg guitar sound (i think they should be more worryed about drums but whateva) i think you should add in more about getting that layerd heavy metal sound. layering 2-4 layers on each side (right and left) can really add that power that people are looking for. i think you did an excelent job writing this

gwailoh
Jan 31, 2006 03:25 am
I think you mean high pass cut
When you mention "Low Pass Cut under 120Hz", I think you mean high pass. You're suggesting cutting the lows, passing the highs. That'll be a high pass filter. Not trying to be snotty, just hoping to avoid confusion for newbies. --Mark

bewst
Jun 06, 2006 11:22 am
In Phase?
Okay, I'm not a recording expert but I do know a little about physics. Unless I'm missing something, it's only possible to get two mics to be "in phase" w.r.t. particular frequencies. Getting the mics to hear the signal in phase depends on the spacing between them a multiple of the wavelength of the sound. If they're off by half a wavelength, they'll be perfectly out-of-phase. Since different frequencies correspond to different wavelengths, it seems to me you can never get them in phase for all the notes a guitar will play. What am I missing?


Dualflip
Apr 06, 2007 02:10 am
Good Article, somethings missing
I think you did a good job in this article, i just think that it should be useful in case of the 2 mic technique to explain a little bit about the 3 to 1 rule to avoid phase cancellation, and also i think that the compression parameters shouldnt be those you specified, dont get me wrong i use those ratio, attack, release parameters sometimes but it should be noted that the compressor should be adjusted to what the sound needs and not as a general rule.
In response to bewst question about different frequencies phase cancellation is this: whenever you use two mic's, you are going to get some frequencies cancelled, the thing is to place the mic where less frequencies are being affected, or to avoid placing the second mic where there is a 180 cancellation eg. two mic's facing each other front to front with the source in the middle of them, in which case you could use a phase invert switch(if your mix board has it) or a plug-in that makes the same job. That is another useful technique i use when miking guitar amps, one mic facing the speaker, and the other in the back of the amp (when you have a back open amp) but remember to invert the phase of the second mic in order to get both mics in phase.


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