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TRACKING ACOUSTIC GUITARS

 

Takamine acoustic guitar

Takamine acoustic guitar

 

If you take a close listen to the sound of acoustic guitars on a lot of recordings, they sound pretty average in a lot of cases.

This is largely when they are functioning as a rhythm instrument, strumming either alone or doubled, or even tripled or quadrupled.  It can also happen whenever there are a lot of instruments playing at the same time.

The acoustic guitar, strummed across al six strings rhythmically, can take up a sizeable chunk of sonic real estate in a mix if left as a full-frequency sound, so it is common to band-limit the acoustic guitar tracks, which simply means that some of the frequencies in their sound are discarded, to allow more room for other sounds sharing the mix space.

There is always a priority to what is the loudest sound in a mix at any moment during the song, and the acoustic guitar is not likely to be particularly high on the list unless its the main (or only) instrument in the song, and very often where it is used alone in an intro before any other instruments start playing.  Even then, it is commonly band-limited by automation of an EQ.  First, so that it is full-sounding and natural in the intro but then changing to a different filter setting (and/or EQ setting) so that it thins out adequately when the bass and drums and keyboards are all in, carving a space for them as it were.

USE A GOOD GUITAR

Assuming you remember to check your tuning regularly between takes, it all starts with a good acoustic guitar.   The spot in the room you choose to play in can also make a big difference.  I suggest walking around the house strumming and picking and seeing where the sound comes alive the most.  Not in the sense of excess reverb (bathrooms) but in the sense of a musical zest, a liveliness to the sound and a rich bloom of overtones.

Change the strings and play the guitar for at least an hour or more if you can before recording.  Ideally, you would play the guitar for a few hours two days running and then record if you want to have the optimum balance of bright added zing (from newness) and richer, fuller tone (from having calmed down a bit by being “played in”).  If strings are played in, this allows the tuning to remain stable for longer periods but you should still check at regular intervals that you are not drifting.

Walk around your home studio (and the rest of your home) looking for places where playing the guitar really sounds great to you, then record yourself playing it there.

Watch out for excessive booming qualities in the low mids and for sympathetic rattling from nearby cutlery drawers, cupboards, display shelves, things like that.

Remember that you can always “edit” your acoustic surroundings by changing them before recording begins.  You might buy a sheet or half-sheet of plywood to keep around and lay it on the floor or lean it against a wall to enliven the sound of your acoustic guitar.

If there are nearby forced air vents or loud humming appliances, it would be wise to turn them off temporarily while you record.  Leave a big note about powering them on again so you don’t lose your frozen food stash.

NASHVILLE TUNING

Using alternate tunings can add a lot of spice.  There are many great alternatives to standard tuning of acoustics, such as DADGBD, DADGAD, EADGAD, EAEGBE and so on.

Very popular due to its excellent functionality within a mix and its bright, feathery jangle is the Nashville Tuning.  To work in this tuning, you will need a set of strings for a 12-string and a set for a normal acoustic, using only some of the strings from each set.

You simply use the thinner “octave” strings from the 12-string guitar set of as replacements for the low E and also the A, D, and G strings on a standard acoustic, tuning them an octave higher than normal, as they would be on a 12-string acoustic guitar.  The B and the high E are normal strings from a set for standard acoustic guitar.

Recording acoustic guitars twice playing the same part (double-tracking) while tuned to the Nashville Tuning, is an excellent way to get bright jangles into your music, and to minimize the accumulation of  muddy lows that tracking multiple passes of acoustic guitars can introduce.  You can also layer a standard guitar tuned instrument and then a Nashvllle-tuned one as a less airy, more solid take on this.

RECORDING IN STEREO

Ideally, all your acoustic guitars would be recorded in stereo because it sounds so good, but in practice, you need to consider the instrumental density of your song’s production.

There is only so much room in a mix in terms of numbers of sounds playing at once.  The more things play at once, the more frequencies are deployed, and you can only have so much energy in each frequency band in a well-balanced, genre-appropriate broadcast-quality mix.

Yamaha FG-420L acoustic guitar

Yamaha FG-420L acoustic guitar

 

Recording the acoustic guitar in stereo adds the WOW factor immediately, but, of course, phase cancellation is a risk factor here that must be considered.

You can either use a single stereo microphone, or a “matched pair” of microphones, which means they were factory-matched for their frequency response, allocated consecutive serial numbers and sold as a matched pair.  They may or may not have been consecutive in their manufacture, since the matching frequency response within tolerance is the important part of the equation.  Consecutive manufacture does significantly improve the odds of a good pairing.

If you like, try using any two microphones in your collection to experiment and see what you come up with.  It is not obligatory to match pairs, but that does assist with a polished, classy acoustic guitar tonality in the mix that works well across the stereo image.

I’ve had great results using a Neumann TLM102 (a medium-size condenser) aimed at the bridge and a Shure SM81 (a small-diaphragm “pencil” condenser) aimed towards the 12th fret, and on a budget an AKC C1000s can get bright (sometimes brittle) results.

Pencil mics have the strong advantage of allowing the player to move more freely relative to the mic positions, since they exhibit much less unwanted tone changes than will occur using their larger cousins when the guitar moves around in front of the mics a lot.

Alternatively, you can try using two condenser mics that can be set to an omnidirectional pattern.  This has the advantage that there is no proximity effect, so less booming, and there is no off-axis aspect to the sound, since all sound is on-axis to an omni capsule.   Together, these two points mean that the player can again move freely relative to the mic positions, within reason.

THE 3:1 RULE FOR USING MULTIPLE MICS

Using the famous 3:1 Rule will save you from phase problems when using two separate mics to record in stereo.  The mics need to be at least three times as far apart from each other as they are from the guitar in order to prevent phase issues arising.  If you place a microphone about 12 inches from the guitar, you need to be at least 36 inches away from the other mic.  For a pair of mics 8 inches from the guitar, keep them at least two feet apart from each other’s capsules.  And so on.

Remember the 3:1 Rule, and use it at all times when you use more than one mic on a single source, such as when capturing a drum kit.

Using one microphone only, you can get a good sound, but do avoid aiming directly at the booming noise emanating from the soundhole – that is there to project at a distance, and allow the lows to build and blossom towards the audience, but typically your mics are placed very much closer than an audience would be sitting.  You don’t want this boom, since it simply eats up precious sonic real estate (headroom) in your mix, forcing you to have a quieter level master at the end of the day, and potentially muddying up the tone of the entire mix, obscuring other important elements.  Try aiming around the 12th fret where the harmonic overtones are rich and prominent, adding interest and brightness, and the boom is minimal.

Warm, rich sustain is fine, but booming low mids and swirling clouds of muddy tone are not.  The difference is usually made by cutting a gentle and mildly narrow dip across the 250Hz to 350Hz area somewhere, maybe one or two dBs will do it, wherever it seems to provide the magic result of opening up the sound and letting other elements breathe in that frequency area, but without emasculating the acoustic.

Gentle EQs are helpful with acoustic guitars, but remember that the more dramatically you EQ them, the more trouble you will have fitting them into a mix.

Over-use of EQ is a serious problem in getting the overall balance of instruments right throughout a mix.  Corrective EQ is fine, of course, but do try to get the sound in the ballpark as you record it.  you may need to do a few brief trial and error recording takes to establish what you are getting, since the guitar will be loud in the room acoustically as well as in your headphones (assuming you send yourself a click to play to).

FRET NOISE AND ROOM TONE

Fret squeals are not usually a big problem, though brand new strings will squeak like crazy for the first hour or two, so do play them in a little bit if you can!

Fret noise is actually a component of the sound that I think adds great realism and humanity, so I like to minimize it and keep what I get.  Trying to remove it entirely does not produce a satisfying result, I think.  De-essers can help with this, if you insist!

If you start a song with an acoustic guitar on it’s own, or any solitary sounds, which is very common as an arrangement technique, then you should capture a little room tone, and the acoustic guitar mic is a good place to do this.

Simply leave the mic set up and recording from where it is placed for capturing the intro part, and, with nobody in the room, record the silence of the room for a minute or so on a spare track.  Make that track inactive and save it as a useful audio file for mastering purposes when you come to master the song.  It will make it far easier for you to place this song next to another song in a natural, engaging manner (at each end as required) in an album or EP’s running order.

DYNAMICS PROCESSING DURING RECORDING

It’s not necessary to compress the acoustic guitar at the time of recording these days, since the DAW can do it all later and there is no noticeable penalty for keeping the input levels low enough to avoid sudden peaks clipping the input.

Using a plug-in will introduce unacceptable latency in most cases, unless set up appropriately in your DAW (see the DAW manual) and I prefer to use hardware compressors for this purpose anyway.

In order to manage the transients that leap out when someone strums an acoustic guitar vigorously, it is helpful to compress, but it can be left safely until later if you just keep the peaks at no more than,say,  -6dBFS or so.   Compression is next to impossible to remove once you’ve added it, so be very careful.  It’s very easy to overdo this and you can’t fix it later.  It can take quite a few years of critical listening to really develop a good ear for the subtleties of a compressor’s action upon a signal.

Settings to consider depend on the model of guitar and it’s construction method, the player, the strings, the room you are in, and so on and so forth, so there is no set way to do this.  Using general principles, however, I can offer the following likely settings to try.  Remember, you can’t undo the compression later, so be gentle.

Start with a 4:1 ratio, 5 ms attack, 35 ms release, and use the hard knee setting if you have a choice.  Once you get that ready, set the threshold.  This is the really important part – the lower the threshold, the more the compressor will react, and you don’t want that.  You need to get the compressor to work on only the sudden peaks that MUST be evened out to prevent clipping.  It should not be audible at any other time.

You can also use limiting for this purpose, but the ratios are very, very high in limiting, such as 20:1, and so you may well find it safer to deal with compression while you get the hang of setting these controls up, and then try limiting the acoustics for comparison with compressing them at much lower ratios.

The end result of your compression settings being set up incorrectly could be a pumping effect.  This may actually be good for the song, although queasy if overused, but remember it can’t be removed or undone.

The pumping effect usually only works when it’s related to the tempo of the track, and you can use the attack and release settings to tweak this aspect.  You can always do this in the mix rather than while you are  tracking.  Again, pumping effects are permanent – be careful out there!

ACOUSTIC GUITAR SOLOS

Regardless of the type of strings you fit to the guitar, you will usually get the best sound from a ‘live’ environment.   If the room is quite dead-sounding, add a sheet of plywood on the floor to help the mics pick up some subtle early reflections from the plywood.

Although it can vary with what you are after, normally it’s important to make the solo as upfront as the lead vocal, passing the baton if you will, so the solo leaps from the speakers to the forefront of the mix and gets all the attention.

Take a listen to what you hear at different distances from the guitar to find a good position for the placement of your microphone(s).   Getting a rich sound in the room makes a big difference in the solo’s character.  The distances to choose depend on the part, the player, the instrument and the room sound, so there’s no right answer here.

Usually, stereo is ideal for a solo, and the AB stereo miking method will give you the slightly exaggerated width expected of a typical pop or rock acoustic guitar solo.  This is the method where you aim your two mics from opposite ends of the guitar, one at the bridge and one at the 12th fret, as described already, following the 3:1 Rule in their placement relative to each other.

XY miking a Takamine acoustic guitar with a matched pair of Neumann MK184 mics

XY miking a Takamine acoustic guitar with a matched pair of Neumann MK184 mics

 

For a more natural sound, less impressive but quite elegant and very mono-compatible (very phase-coherent), you can try the XY method of stereo miking, where a matched pair of pencil condensers are mounted a few inches apart on an XY mounting arm (a little attachment for a micstand) and turned such that their capsules meet so they can form the shape of an X together.  This is also called the coincident placement technique.

Most budget stereo mics, including those fitted to the Zoom range of portable stereo recorders, for example, will consist of an X-Y mounted pair of condenser capsules on a single body housing, requiring a single micstand but giving a stereo output signal of two channels.

The mics are angled towards each other.  Narrowing or increasing the angle of the X will shrink or expand the apparent width of the stereo image produced when hard-panning the resulting pair of tracks opposite each other in your DAW, and some fitted XY capsules allow you to rotate them to achieve this.  The natural sound of XY is good for non-pop music, classical, jazz, etc.  It sounds very real on headphones, for instance, and collapses to mono perfectly well.

For dance, electronic, pop and rock styles, you will want your acoustic guitar solo to be in AB stereo most of the time, for it’s greater dramatic presence and width.  You do need to pay attention to the 3:1 Rule for this, but you can have some huge sounds as a reward.

The Rode NT4 1/2″ condenser XY coincident stereo microphone is a great example at a reasonable price for a standalone stereo mic.

You might try M/S (Mid/Side) miking techniques too, both for strummed acoustics and for solos.

MID-SIDE TECHNIQUE

Many stereo mics can be set to work in a Mid/Side configuration.  It’s pretty simple to do if you have a cardioid mic (the MID mic) and a figure-8 pattern mic (bidirectional, for the SIDE mic).

Aim the cardioid pattern mic at the source (that’s your MID signal) and aim the figure-8 so that it’s null position faces the source (point of maximum rejection of sound, at right angles to the live sides of the mic) and it’s live sides are therefore now perpendicular to the source (the SIDE signals).

Record the MID mic’s output to a single mono track, panned to 12 o’clock for playbacks.  Simultaneously record the SIDES mic’s output to another pair of mono tracks, duplicating the signal to do so and panning them opposite each other, one hard left and the other hard right.

So you now have three mono channels (or one mono and one stereo) in your DAW for the acoustic guitar.

Panning, the MID channel goes at 12 o’clock and the two identical SIDE signals go fully hard-panned, each  opposite to the other.

When combined, the signals from the two opposite-panned copies of the SIDE mic are in opposite phase to each other (it’s a bipolar mic, remember) and so the opposite polarites cancel each other out upon summing to mono, leaving you with only the sound from the solid MID mic in your now mono mix.  The cardioid mono mic becomes your solo sound.

When you are in stereo, however, you have a lovely sound using MID and SIDE signals judiciously mixed together.  This provides a sound that can have it’s stereo width adjusted at will AFTER it has been recorded, since you can narrow the width of the image towards the mono version simply by reducing the level of the SIDE components in the mix, or alternatively by panning them inwards a little further towards the middle, which will narrow the apparent width of the sound you are getting in stereo.

The left/right stereo is created in M/S recording from combining the sum of MID and SIDE signals for one side, and leaving the difference between MID and SIDE signals for the other side.  This is called sum and difference monitoring, and is interchangeable with stereo monitoring.

Literally all stereo signals, including all commercial stereo mixes, can be converted to M/S signals simply by performing the sum and difference moves on the signal and monitoring them that way.  Then you can convert them right back to stereo by doing the reverse.  It is just another way of dealing with the information contained within a stereo pair of channels.  It takes three channels to view it as M/S data, however, and you just collapse back to two for stereo conversion.

It’s a very natural and unforced sound, with not much drama, but it’s beautiful to listen to, has wonderful phase compatibility in mono by collapsing to MID only, and has the unique advantage of letting you change the size of the image after the fact at mixing time.  This can be very useful to make space in a busy mix.

The only real issue is that you don’t want to raise the SIDE signals louder than the MID signal because this will cause the mono centre to become poorly defined, provoking a “hole” in the middle of the image, or a “phantom centre”.

Best practice is to begin with the MID side nicely loud in the centre of the mix at 12 o’clock pan position, then raise the SIDE signals together as a pair until the image widens nicely.  Don;t get louder than the MID.

MIC CHOICES

Pencil condensers are the best choice due to the detail and brightness, but many types of mic work well and really, the choice is not desperately important most of the time, since most of the time the acoustic guitar is joined by many other instruments on a recording.

Ribbon mics may be nice sometimes, being warm and mellow and rich, but may not be bright enough.  They also require rather high gain preamps, which can lead to high noise levels if incorrectly set.

If you can filter out frequencies below 100Hz at the mic, do so.  You should not need a pad engaged at the mic.

Dynamic mics will work, especially on percussive, rhythmic parts, but generally they don’t react as quickly to the transients and are not as bright as pencil mics.  The sound is simply too hard in the midrange, most of the time.  If you want a warm, rich, full sound with plenty of detail and airy highs, you will want to try a large diaphragm condenser mic, which is great too, but more expensive.

USING AN OMNI PATTERN

You should also try the omni pattern on your condensers, since they sound great on an acoustic IF the guitar sounds great in the room too.  Assuming your sound is good at source, the omni pattern can be very realistic and works very well for strummed acoustic guitars or mandolins.  Using an omnidirectional pattern also ensures there will be no proximity effect (no boosted lows) when the player gets within a few inches of the mic, which is possible if they are about six inches to eight inches away from the mic at the start of the take.

Another great advantage of omni patterns is that you can put more than one musician around the mic, and if they are the same distance they should sound balanced together well, since the players will acoustically balanced themselves by ear in the room as they play.  Musicians do this naturally, so if you have another good player playing with you, you simply need to allow for them to do the balancing and preserve what you get.  Automation may well be unnecessary.

This is as opposed to recording into two separate mics, balancing them yourself in the mix using automation, which can take a fair bit of time and may not work as well.  There is a certain sense of space in using omni mic patterns (due to room sound components) and it is easy to make use of them.  Put a circle of acoustic guitarists around an omni pattern large-diaphramg condenser and sound like a Traveling Wilbury.

ACOUSTIC GUITARS WITH A 1/4″ JACK OUTPUT

If there’s a jack socket mounted in the guitar body, then there’s a pickup system on the guitar.

There will be at least one knob somewhere on the instrument, often near where the neck joins the body, on the side of the guitar.

You may have tone controls, sometimes in the form a small graphic equalizer with lows, mids and highs, or in the form of a pair of rotary pots, one for bass, one for treble.  There will be a volume control and it often doubles as an On/Off switch.

Takamine onboard acpoustic guitar preamp with graphic EQ.  Note battery compartment and B-CHK (Battery check) for the active electronics

Takamine onboard acpoustic guitar preamp with graphic EQ. Note battery compartment and B-CHK (Battery check) for the active electronics

 

Note the Takamine acoustic/electric guitar shown above has a battery compartment, since the fitted active electronics require power to function, supplied by a 9v PP3 battery, the type usually found in guitar pedals.

The sound is distinctively acoustic/electric, and quite unlike an acoustic guitar that is recorded via a microphone.   It is simply not as engaging to my ears as the sound recorded in a real space with a microphone, and most people agree on this.  Make your own mind up, but I think you’ll probably find yourself using a mic a lot more than a DI.

It is extremely unusual for people to record the acoustic as a DI with the intention of making it the main guitar sound, but it is often captured as a DI for safety, and for an alternative tone.  None the less, it is the norm to record with a mic, and use the DI as a safety copy.  Its great to have the option of adding a bit of the DI to the sound when you are mixing, and if the mic recording is spoiled by room sound of some sort on a great take you can’t possibly repeat, the DI will be there to save you.

Enjoy the process, and experiment with different mics, different distances, different spaces in the room, different rooms, and with bits of plywood for reflective assistance.  Have fun!  There are no right answers with acoustics, since a million different sounds are available.

My next blogpost will be on recording electric guitars.  See you then!

 

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