By pick-up range of a source (e.g. an acoustic guitar) we mean the degree of proximity of a microphone to the source, also referred to as 'presence'.

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Microphone fields

Various factors must be considered when defining a microphone field, such as:

• the side of the source from which the shot is taken (front, side, back)
• the amplitude of the instrument's sound front (small for a woodwind, medium in the case of a flute or guitar, large for a drum kit or grand piano, very large in the case of a pipe organ, large choir or symphony orchestra)
• the distance of the shooting point from the source
• the directional characteristics of the microphone, i.e. its polar figure, which make it capable of 'embracing' a wider or narrower pick-up angle

Having said that, let's start by defining what, in phonics practice, turn out to be the six main fields of view, which in turn can be organised into two distinct categories:

Main fields

1. internal field
2. proximity field (or presence field)
3. resonant field (or body field, or quality field)

Secondary fields

4. long range
5. field set
6. reverberation field

Main fields

Internal field

It will not always be possible to use the Internal Field because it presupposes that the microphone is placed inside the instrument.

The resulting acoustic pressure will be very high, as will be the isolation from other sources, but the quality of this pick-up will never be excellent, because the natural sound will be strongly compromised by various very strong dominant resonances, due to the extreme proximity of the microphone to certain sound elements emitted by the instrument with respect to others.

Some components of the sound, in fact, will tend to clearly predominate over the others, so it will be easier to use this technique with percussion instruments with fixed pitch, such as drums, provided that you work hard with the equaliser, during the tuning phase, to restore an optimal balance between the aforementioned elements that make up the totality of the sound, sometimes obtaining very good results despite being quite different from the sonority that can be experienced when listening to the instrument acoustically.

As is well known, internal field imaging is used as standard for rock-pop bass drums, inserting the microphone through the hole in the skin behind it.

The same shooting technique, which was very popular in the 1970s and 1980s, can be implemented with certain types of tomtoms without the lower skin.

Some uncommon snare drum and tomtom models are equipped with a hole in the drum, into which a small microphone can be inserted, to be placed somewhere between the two opposing skins of the drum.

As an alternative to the above, it is good to know that there are mechanisms available that can be mounted inside the drums of all drum models; they allow any type of microphone to be fixed internally (e.g. consider the Randall May International kits), achieving a result of high practical utility that, however, not everyone appreciates in terms of sound quality.

As is obvious, it is also possible to insert a microphone inside the guitar pit or inside the lid (even closed) of a grand or upright piano; despite careful intervention with the eq, even if it improves it, it will almost never be possible to obtain excellent results, even if it is possible to optimise the result provided you use special microphones created especially for this extreme use.

Beyond the controversial opinions, here is an objective summary of the pros and cons of using this shooting technique:

Pro

• sharp reduction in sensitivity to themicrophone trigger (Larsen) caused by the return of the P.A. and/or stage monitors during amplified concerts, which makes it especially favoured in live performances, as well as the following characteristic
• extreme isolation of the microphone from other very close sources (e.g. from the other 'pieces' of a drum kit, including cymbals),
• almost total isolation from environmental influences such as noise and room reverberation
• very high pick-up sound pressure, capable of optimising the signal-to-noise ratio to the highest degree during amplification (live) or recording

Against

• deformation of the tonal spectrum and to some extent also of the dynamic balance of the sound; these drawbacks will be more easily resolved on instruments with constant pitch such as percussion instruments, while they will be more difficult to resolve on instruments with variable pitch; the technique must be combined with a very sophisticated equalisation intervention to restore a sufficient level of tonal linearity to the instrument
• risk of mechanical distortion of the microphone diaphragm (or, worse, its rupture) if microphones with low mechanical resistance are used; for example, a microphone placed inside a snare drum could pick up sound pressures in excess of 150 dB
• risk of distortion of the electroacoustic signal and/or digital clipping if the PAD attenuation filter on the GAIN of the preamplifier or mixer is missing

Proximity field

The Proximity Field and the Camp Resonance, which we will consider in a moment, are both and rightly the most widely used in most applications, both live and in the studio.

Unlike the internal field, the proximity field is implemented with an external shot very close to the instrument, called close-mic (close miking).

It is directed towards a point that, while not being able to homogenously embrace the entire resonant body of the instrument, allows it to express 'the substantial part' of its timbral content, without introducing too many acoustic defects.

Each sound source has its own ideal shooting point for the best performance and it will be up to the sound engineer to 'find it', positioning the microphone (or stereo microphone set) appropriately and with great care, knowing that at such a close shooting distance, the slightest movement of the microphones or the performer will result in considerable timbre and volume shifts.

Here, then, is a summary of the pros and cons of using this shooting technique:

Pro

• great incisiveness and clarity of attack transients
• good isolation from ambient noise and room reverberation
• good sound pressurewith moderate risk of mechanical and electroacoustic signal distortion in the case of very dynamic sources
• good resistance to triggers (in live events)
• good compromise between quality (in terms of sound completeness) and presence, in favour of the latter in particular

Against

• excessive incidence of mechanical noise and resonances compared to the body of sound
• relative harmonic poverty in the timbral fabric of the sound tail (which is the support of the audible sound after the attack transient)
• risk of distortion of the microphone diaphragm or preamplifier input when shooting very dynamic sources
• even considerable tonal and volume swings in the event of even slight movements of the sources from the microphones during performances

Resonance Field

A correct resumption of the Resonance Field (also called body field o body fieldor even quality field) is achieved when the pick-up angle of the microphone can fairly evenly embrace the entire resonant body of the instrument, 'straying' a little outside it.

This is achieved by simply moving the microphone as far away from the source as necessary.

This technique is widely used in recording studios as it is generally the one that allows the best timbre response of the source in comparison with acoustic listening at an 'intimate' distance; however, it requires good acoustic treatment of the recording room due to the 'important' level of penetration of acoustic reflections returned by the room walls.

This technique is often not recommended for amplifying sources during live concerts, especially in the case of many neighbouring concurrent sources, or a high amplification volume of the P.A. or monitors, while it is very effective for recording-only footage even during a live event.

The following are the pros and cons of this shooting technique:

Pro

• excellent sound fidelity in relation to the acoustic original
• great timbral richness and tonal balance
• good attack transients
• still a good compromise between presence and quality, especially in favour of the latter
• low risk of mechanical and electroacoustic distortion during filming
• good tolerance in case of small source displacements relative to the microphone
• lower incidence of mechanical noise occurring during sound production

Against

• high possibility of triggering (in live events)
• excessive incidence of reverberation in poorly acoustically treated rooms
• excessive incidence of unwanted environmental noise in poorly insulated environments

N.B.

The aforementioned presence fields are the most commonly used, as a basis, for live and studio sound recordings.

Environment fields

Long field

Compared to the resonant field, the Long Field is obtained by moving the microphone further away from the source, but keeping it perfectly on axis so as not to lose the "focus" on it, while including a significantly higher percentage of reverberation in the shot, which should however not predominate but at most equal that returned by ambient reflections (thus the length of the field should be commensurate with the characteristics of the room resonance).

In all cases of music production, it will be imperative that the recording environment is properly treated to provide a pleasant and balanced sound, as free as possible from resonances on particular frequency bands (typically stationary resonances and modal frequency cancellation nodes).

The long field makes it possible to obtain very lifelike recordings, similar to those heard by the ear at an acoustic concert, so it is suitable for recordings (typically in stereo) of large orchestral and/or choral ensembles or for obtaining footage capable of recreating the suggestion of an acoustic concert in a theatre (sometimes used in combination with other, closer, sectional filming techniques).

The technique is often used for sound recordings aimed at video production, when a sound corresponding to the same field represented through images is desired.

With this technique, the sound and musical content of the performances still retain a good definition, although they are represented with less 'presence'.

The long field can also be used in the recording studio, in combination with the proximity field, to be able to dose the presence, body and ambience of the sound in the mix.

Setting field and reverberation field

These two techniques alone are used for special effects or even in videography to suggest the idea of an 'off-screen' or even an 'outside field' sound.

Sometimes they are used in the studio for secondary roles, in combination with the proximity field or the resonance field, in order to be able to dose the desired amount of room reverberation in the mix.

For Ambient Field refers to a shot taken from a point far away from the source, where the reflected sound clearly predominates in intensity compared to the direct sound.

For an atmospheric, 'phased' shot of the room, the Blumlein-type stereo panoramic shot technique can be used using two bidirectional microphones with a 'figure-of-eight' polar figure (shooting from the front and back of the microphone but not from the two sides).

To accentuate reflected sound as opposed to direct sound, the XY technique can be used instead of the Blumlein, turning the pick-up axis towards the ceiling or a wall opposite the source

The Reverberation FieldOn the other hand, it is obtained by ensuring that the stereo shot (typically carried out using the Blumlein technique) does not contain the direct sound, but only the reverberation; to obtain this condition, the microphones of the stereo set can be arranged exactly as for the ambient field, but interposing a large acoustic screen between the source and the microphones (but not too close to the latter), so as to cancel the capture of the direct sound of the source and the first reflections, and thus capture only the sound of the ambient reverberation.

Mono, stereo and mixed shots

With the exception of the indoor field all other fields can be shot in mono or stereo.

For stereo proximity imaging and stereo resonance imaging, it will be possible to use the XY technique, with the capsules overlapping or side-by-side (as the case may be) but always offset from each other at an angle typically between 60° and 90°, and arranged so as to direct the intermediate pick-up axis of the two microphones towards the source (see the figure below regarding stereo imaging, visible on the right).

As is obvious, this will bring the microphones even closer to the source due to the increased total pick-up angle.

This solution is particularly interesting for the proximity field, as the double microphoning required by the stereo set will make it possible to reduce to a large extent the acoustic distortions induced by the extreme proximity  of the source to the microphones.

In this way, thanks to the XY stereo set, the proximity field will be able to capture the entire resonance field of the instrument, while maintaining the extreme presence, brilliance and incisiveness of the proximity field's own transients.

In certain cases, one might decide to shoot the source in mono or stereo through a proximity shot and, in addition, with a second stereo set in the resonance or long range, and then dose the 2 sources in the mix phase.

Time lag in multi-field shooting

Consider that by using several microphones aimed at the same source but placed at different distances from it, the pick-up times will vary, creating more or less temporally offset tracks in the mix, with the following result:

• attack transients not perfectly coincident
• changes in the tonal spectrum due to the onset of the comb filter

The issue will be of little importance when one only intends to add a pinch of ambient field to the presence field, while maintaining the proportional acoustic volumes of the shot (volumes which, due to the different distance between the two microphones, will be very high for the presence shot and very moderate for the ambient shot); in this case the shift will be able to determine very pleasant effects, and the phase shift will be acceptable due to the lower volume incidence of the farthest shots compared to the closest ones.

Example 1

A shot of a guitar taken in the proximity field at a distance of 20 cm and, at the same time, a shot of the same guitar, on axis, in the resonance field at a distance of 85 cm. At such distances, the resonance recovery delay will be approximately 2 ms. As we know, the intensity of the sound pressure decreases quadratically as a function of doubling the distance, so at 85 cm it will be about 1/16 (which would mean a natural reduction of the direct sound of about 12 db (partially attenuated by the reflected part of the sound, which will instead have a similar volume in both microphones). A 'natural' shot and mix would respect these proportions, making the time lag absolutely negligible.

Example 2

The opposite is the case if you want the 2 tracks to be reproduced at identical or very similar volumes, which will be achieved through adequate enhancement of the gain of the more distant shots (in this case about 8-12 db); the aim in this case would be to create a 'whole' between the two shots, so that the volumes of the two fields can be dosed at will until the preferred effect is obtained. In this case, therefore, the attack transients of the tracks corresponding to the two fields should be positioned in perfect synchrony.

The alignment of the attack transients can be obtained by suitably delaying the footage of the closest microphones by means of a delay plugin that can be installed on the track, after a precise calculation of the delay; to this end, we consider that 33-34 cm of distance (approx.) cause a delay of about 1 ms (1 millisecond) and that each ms contains 44.1 or 48 or 96 samples (in digital sessions at 44.1, 48 and 96 khz sampling frequency respectively), so with this data you can easily calculate the right compensation, adjusting the plug-in delay accordingly (which is usually expressed in samples and/or ms).

For a more reliable check of perfect alignment, a test recording of a few seconds duration could be made, and then the perfect alignment of the transients of the two tracks could be checked on the timeline. For better monitoring of the resulting sound already in the recording phase, it would be better if the alignment was done before recording, but in any case it will always be possible to perfect this alignment posthumously by delaying the near-field track until it collides perfectly with the other. At this point, it will be possible to freely decide on any proportion between the two fields, concentrating only on the desired type of sound, without incurring serious phasing problems and ensuring the perfect focus of the transients.

It goes without saying that the delay can be brought exactly into synchronisation or kept somewhat 'loose', should it be found that the sound result is more pleasant or more functional to the context; for a better choice, one should first listen while keeping the two fields at the same perceivable volume.

The directivity of microphones in the pick-up fields

The wider the pick-up angle of a microphone, the smaller the distance needed from the sources to obtain the above-described pick-up fields.

Example

For an acoustic guitar, position a super-cardioid microphone (i.e. with a useful pick-up angle of approximately 70°-90°) at the right distance to obtain a correct pick-up in the resonance field; replacing the microphone with a cardioid type with a pick-up angle of 90°-110° will allow you to get closer to the source while retaining a similar pick-up field; similarly, using a semi-panoramic (180°) or panoramic (360°) microphone will allow you to get even closer.

With the panoramic microphone, a slightly different effect will be achieved due to the higher incidence of ambient reflections picked up by the capsule.

It will then become clear that, for the same desired field of view, as the directivity angle of the microphone increases, it will be necessary to bring it closer to the source. Proximity will decrease the proportional incidence of ambient reverberation, also optimising the signal-to-noise ratio (relevant in the case of very weak sound sources). 

Extreme proximity will, however, make the instrument's sound components emitted in front of the microphone stand out more than the more peripheral ones, thus decreasing the linearity and thus the fidelity of the natural pick-up, which will be partly restored if a semi-panoramic or panoramic microphone (which is practically free of proximity effect) is used or if the cardioid microphone is moved away from the source.

Choice of shooting field according to role in the mix

A good rule of thumb would be for each microphone take to include the recording of several fields in different tracks, so that they can be appropriately chosen or dosed in the subsequent mix phase.

If, for example, one were to record an acoustic guitar using proximity and resonance pick-up at the same time, after precise alignment of the attack transients, it would be easy to adjust the balance between body and presence, and also between softness and attack, simply by adjusting the volume of the two audio tracks.

In this way, the judicious use of multi-field shooting could result in balanced and full colourations that may already be satisfying in the mix, without massive use of the equaliser and artificial reverbs.

This way of recording will be particularly relevant for sources with a solo role; it will also be relevant with rarefied arrangements, while it will be less important with denser ones (where it will often be preferable to avoid using multi-field tracks in order to make the tonal thickness of the sources smaller, rather than larger).

In situations where a source is a non-predominant element, one will often prefer to record using only the proximity field; in this way, the sound will be poorer and not very resonant but much drier, 'smaller' and more defined, and thus more suitable for embedding in a mix consisting of numerous sources (such a sound will in fact have a reduced capacity for tonal masking; in doubtful cases, one may decide to record both main fields and decide later on 'what to do'.

Use of environment fields

We have considered how the use of ambient fields, used on their own, is of secondary utility, being limited to videographic uses, to coherently accompany fields already represented visually with the sound element.

The long field is used where one wants to acoustically represent a source that is not very present, with a somewhat distant, moderately set field, in an acoustic live theatre dimension.

The ambient field and reverberation field, alternatively, can be easily simulated through the appropriate use of digital ambient processors.

As a possible alternative to the resonance field, it may be interesting to combine a long field or room shot with a proximity shot, to be dosed in the mix.

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