Understanding Nearfield Miking

Extreme close miking can be an aesthetic choice or an uncomfortable necessity. Either way, it’s important to know how to get it right.

Ever since multitrack recording was invented, it’s been common to mic every instrument individually. That’s true both for live ensemble recordings and for more ‘produced’ records built up through layers of overdubbing. Sometimes the individual mics are used to augment the capture from more distant mic arrays, as with spot mics on orchestral instruments, or close mics on snare and toms in a drum kit. Often, though, it’s the individual mics that provide the main or the only capture of each source.

When we record like this, one of the main concerns is separation. If there is more than one instrument playing in a single space, we want to be able to capture the sound of each instrument to a separate track, minimising bleed or crosstalk between them. Depending on the circumstances, we may also want to capture the sound of the instrument without a strong acoustic imprint from its environment.

There are several factors in play here, but usually the most significant one is distance. The nearer the mic is to the instrument, the higher the ratio of wanted sound from that instrument to unwanted sound from other sources and room reflections. In a close position, the mic also encounters a greater absolute sound pressure level from the instrument. This can be an important consideration with quiet acoustic sources, because it helps to deliver a higher signal‑to‑noise ratio.

The importance of keeping the distances from source to mic short is well known to live sound engineers. In a typical stage environment, not only is there no baffling or other acoustic separation to block spill from other instruments, but the sound from our mics is being amplified and played out through stage monitors and front‑of‑house speakers. Moving the mics close to the sources is therefore essential, not only to achieve separation but also to avoid feedback.

Experienced studio engineers, by contrast, are sometimes suspicious of very close miking. In fact, you could say that what we look for in a studio live room is an acoustic environment that makes close miking unnecessary, or at least optional. The beauty of a space like Abbey Road Studio 2 is that you can pull the mics further back from the source without unpleasant coloration, excessive reverberation or problematic leakage creeping in. We’re often told that we shouldn’t be afraid of spill: even that it can supply the ‘glue’ that helps a recording come together. So are there any circumstances in which very close miking might be a positive choice in a studio environment? And what considerations do we need to bear in mind when making this choice? This is a topic that Eddy Brixen has been researching for DPA Microphones, and in this article, I’ll be sharing some of his insights.

It’s no surprise that musicians often prefer a nearfield miking approach, because it is more likely to produce a sound that they are familiar with.

Zooming In

First of all, let’s quickly introduce some theoretical concepts. What we’re talking about here is nearfield miking: positioning the microphone so close to the source that its capture is dominated by sound radiating immediately from the instrument. We are defining the nearfield as the zone around an instrument where the ratio of direct sound to reflected sound from walls, floor and ceiling is high enough that the latter is basically negligible.

The Chapterhouse at Wells Cathedral: some spaces are so reverberant that nearfield miking isn’t really practical!It’s important to note that the extent and location of this nearfield zone varies a lot. In some cases, the shape of the instrument and the properties of the environment might make nearfield miking altogether impractical. I’ve had the good fortune to record a couple of sessions in the Chapterhouse at Wells Cathedral, which is a large octagonal space faced entirely with stone, and capturing a ‘dry’ sound in there would be impossible. By contrast, an anechoic chamber extends the ‘nearfield’ throughout the entire space.

It’s also vital to bear in mind the differences between different musical instruments. In the abstract, we can think of three types of ‘ideal’ sound source: a point source, a line source and a plane source. An ideal point source emits sound equally in all three dimensions. A line source radiates in two dimensions only — for example, it might emit sound horizontally but not upwards or downwards. An ideal plane source would beam sound only in one dimension.

Musical instruments typically display a complex mixture of all three behaviours. Different parts of the instrument can radiate sound in different patterns, which can vary with frequency. In the distant field, all these elements merge together with reflections from the environment to create the sound of the instrument as it would be heard by the audience, at least in an unamplified performance. In the nearfield, there is a tendency for instruments or their component parts to approximate plane sources, and these different elements are less integrated. The upshot of this is that placing the mic very close to the source introduces a number of interesting considerations.

Breaking It Down

With most instruments, very close miking will deliver a sound that’s noticeably different from the integrated whole heard by a distant mic. This is not only due to the fact that less reflected sound is being captured. It’s because any given close‑mic placements will tend to exaggerate some elements of the sound and underplay others. Consider, for example, the various positions where you might place a mic to capture the sound of an acoustic guitar. If the mic is positioned behind the guitar, its capture will be dominated by the resonance of the body. A mic pointing directly at the player’s right hand will pick up a combination of percussive pick noise, direct vibrations from the strings and body resonances. Miking near the soundhole delivers a boomy, woolly low‑frequency sound. Placing the mic halfway up the neck, by contrast, would give you a thin sound dominated by the strings themselves, and would tend to foreground incidental noise from the left hand such as string squeaks.

It’s also worth bearing in mind that the isolation we achieve through nearfield miking can sometimes be undermined by the reflective properties of the instrument being miked. For instance, the open lid of a grand piano doesn’t just help project the sound of the strings outward towards the audience; it can also direct spill from other sources right into our microphones.

Extreme close miking on brass instruments produces a very different timbre from conventional distant miking, but in some genres, that’s become part of the sound we expect to hear.In many cases, musical genres have well‑defined aesthetics in which the use of nearfield or far‑field miking is normal. For example, in a jazz context, an instrument such as the saxophone might be miked up at some distance, or a close mic might be used only to support a distant stereo capture of the entire band. By contrast, a sax solo on a hard rock record would typically be recorded very close up, with any additional ambience added artificially after the fact. Likewise, in pop and rock contexts it’s usual for electric guitar sounds to be captured primarily using mics placed right in front of the cabinet. This is another situation where small changes in the mic position can make a big difference to the resulting sound.

Them & Us

From the recording engineer’s perspective, an alternative working definition of ‘near’ and ‘far’ is sometimes more useful than the technical one outlined above. Understood this way, the nearfield is the soundfield as perceived by the musician, whilst the far field is the soundfield as perceived by an audience. When we look at it this way, it’s no surprise that musicians often prefer a nearfield miking approach, because it is more likely to produce a sound that they are familiar with. The relationship between a musician and his or her instrument is an intimate one, and distant miking can lose that sense of intimacy. There is an important element of feedback involved in playing an instrument, whereby the musician hears what’s emerging and reacts to it. With some instruments, that reaction is captured most effectively using carefully judged nearfield miking. With some orchestral instruments, by contrast, reflected sound within the hall is intentionally a key part of the sound, and must be captured in order to give a faithful representation. The classic example is the French horn, which is usually played pointing away from the audience so as to create a more reverberant sound.

Indiscriminate or inappropriate use of nearfield miking can also lead to problems at mixdown. For example, the player seated at a grand piano hears a wide spread of sound, with high notes to his or her right and low notes to the left. Close miking in stereo can deliver a faithful and satisfying capture of that spread, but it’s important to consider the context of the song. In a simple ballad that has just voice and piano, a big stereo piano sound might be perfect; but if the finished mix needs to balance many instruments playing together, it can be hard to incorporate a single instrument that appears to span the entire stereo field.

To put this another way, it’s often the case that the finished mix recreates or synthesizes the impression of an ‘audience perspective’, even if the band was recorded using only nearfield miking. If that’s so, we need to bear the end result in mind when choosing our miking arrangements.

Miking a piano very close can help retain a sense of intimacy that may be missing from distant placements, but can introduce difficulties of its own.

Miking Up

Whichever definition of ‘nearfield’ we consider, most studio live rooms are designed in such a way as to make this zone comfortably large for most instruments. In many cases, standard studio miking approaches for common sources are nearfield techniques. For instance, when we place a mic on a stand in front of a singer’s mouth, we aim to capture a high ratio of direct to indirect sound, and we also focus the capture on those aspects of the sound that are produced by the head rather than, say, the abdomen.

However, those conventional techniques aren’t always sufficient to meet the goals of nearfield miking. In a difficult acoustic environment, we may need to go even closer to the source to minimise pickup of reverberation or ambient noise. In a performance context, we may need to do more to exclude spill from other instruments. There may also be additional considerations such as the need for performers to move about freely, or for mics to be visually discreet.

For extreme close miking, conventional stand‑mounting is often problematic, especially with instruments that are not fixed in position. If we are miking a saxophone from six feet away, small movements on the player’s part won’t affect the sound that is captured; if we’re miking it from an inch or two, those motions can be all too apparent as changes in level and tonality. There’s also a constant risk of the mic being bumped.

Fixing The Mic

The solution, as experienced live sound engineers will know very well, is to attach the mic to the instrument itself rather than placing it on a separate stand. This is a technique that may be less familiar to studio engineers, and one which typically works best with miniature mics and specialised mounting hardware, though it’s sometimes possible to improvise with what’s available. Whatever method we choose has to meet a number of requirements.

It’s vital that mounting hardware for instrument mics poses no risk of damage to expensive instruments!Firstly and perhaps most importantly, attaching a mic must not place the instrument at risk of damage. The tools used by professional musicians can cost tens of thousands, and may well be irreplaceable, so it’s absolutely vital that whatever mounting system we adopt leaves the instrument unaltered once removed. This is something to be extra cautious about if you find yourself having to improvise or adapt a mount rather than using a high‑quality purpose‑designed system.

Secondly, mounting the mic should not in and of itself alter the sound that the instrument actually makes. This is a risk when attaching heavy weights or large pieces of soft material to a resonating surface, and again, specialised mounting hardware is designed in such a way as to have minimal influence on the sound.

On a related point, the miking technique we adopt must not hinder the player. This is not only an issue with mics attached to the instrument — stand‑mounted mic placement can be equally problematic. Our chosen miking system should not add significant extra weight to the instrument, or put cables and mics in the way of the player’s hands, restrict their movement unduly, or force them to adopt an unusual posture. At the same time, it needs to be stable and reliable: a mounting system is no use if it falls off or shifts during a take.

Finally, of course, the microphone and mount need to deliver the sound we actually want. Ideally, this means giving the engineer some control over where on the instrument it’s mounted, so that he or she can control which elements of its sound are favoured in the recorded signal.

Choosing The Mic

The choice of a mounting system and placement goes hand in hand with the choice of mic itself. As usual, we have the option of employing an omnidirectional or a directional mic. With stand‑mounted nearfield miking, the figure‑8 polar pattern can be useful, especially in situations where sound from one particular direction needs to be rejected. The most common application here is to achieve separation on voice and guitar signals when the singer is also the guitarist. Engineers sometimes neglect the potential of the figure‑8 pattern in other contexts, too; for example, if you’re recording a live band in a venue with a high ceiling, figure‑8 mics as drum overheads can achieve much better isolation than cardioids.

For very close miking, though, and especially in situations where mics need to be attached to instruments, we’re usually restricted to omni or cardioid options. Each has its own strengths. Omnidirectional mics are, in principle, capable of capturing an indefinitely extended low‑frequency response, and at the same time, do not exhibit proximity effect. They are also less vulnerable to wind and vibration noise. And, unlike cardioids, good omni mics do not impose problematic coloration on sound arriving from the rear and sides. This means that any spill or reverberation that is captured should sound relatively natural, but it can also have an impact on pickup of the wanted sound. When a directional mic is placed very close, parts of the instrument itself may be significantly off‑axis.

By their nature, however, omnidirectional mics don’t discriminate between sound arriving from different directions. This means that if we’re using them in a nearfield context to minimise spill, the only thing we can do to increase the ratio of wanted to unwanted sound is to move them even closer to the source. And even then, at a given distance, a cardioid mic pointed at the source will exhibit a noticeably better ratio.

Unlike omnis, cardioid mics exhibit proximity effect when used in this context; and, as explained in our November 2021 article (www.soundonsound.com/techniques/proximity-effect), this can have benefits as well as drawbacks. In the extreme nearfield, most instruments begin to behave more like plane than point sources, so the proximity effect is fairly consistent within a certain distance. A mic that’s placed three inches away from the source usually won’t encounter significantly more bass tip‑up than one placed six inches away.

The proximity effect also provides a helpful degree of free additional separation at low frequencies. Usually, only the instrument we’re actually miking is close enough to cause a significant degree of bass boost, so the proximity effect actually increases discrimination between wanted and unwanted sounds at low frequencies. In a difficult miking situation, even where we don’t want the additional low end, it might therefore be desirable to use a cardioid mic and compensate for the effect using EQ.

Many bass drum mics have a deliberately non‑flat frequency response; not so DPA’s new 4055, which is designed to deliver a faithful capture of the source.Finally, we shouldn’t forget that this bass boost is sometimes exactly what a source needs. Bass drums, floor toms, snares, double basses and other instruments often sound more impressive with the low end boosted, and nearfield miking provides a simple way to achieve this. Be aware, though, that directional mics are usually much less so at low frequencies, and also that their frequency response tends naturally to roll off in that region. Directional mics intended for close‑up use are often designed to have a curtailed low‑frequency response, too, anticipating that the engineer will want to compensate for proximity effect. Mics designed for particular applications sometimes have a frequency response that is deliberately non‑flat in other respects, also, as witness the many bass drum mics that have a very ‘scooped’ midrange.

Up Close & Personal

The important takeaway from the engineer’s point of view is that getting a good sound through extreme nearfield miking can be unpredictable, and often involves plenty of trial and error. Moving a mic a few inches along the body of an instrument can completely change the character of the sound that is captured, and the differences between mics are also very apparent in these circumstances. It’s important that your equipment supports the choices you might want to make here, making it easy to vary mic types and positions. Nearfield miking isn’t the right choice for every situation, but the skills and the equipment to handle it should be part of every engineer’s toolkit!  

Thanks to Eddy Brixen and DPA Microphones for their help with this article.