Miking

from Wikipedia, the free encyclopedia

Under miking or Mikrofonierungstechnik one understands the situation-based selection and preparation of suitable microphones for picking up sound sources. Their directional characteristics and frequency response determine the areas of application. A different sound is achieved depending on the location and the microphone arrangement as well as the mixing of the signals.

The term miking is often confused with microphony , which refers to a disruptive effect in which electroacoustic components not intended as microphones work unintentionally as sound transducers.

The approach to miking sound systems , recording sound in music or recording technical sounds is very different. When it comes to sound reinforcement , it is essential to reduce the risk of feedback from the loudspeakers . That is why one goes very close to the sound sources here, which u. a. leads to a proximity effect . The close-up effect is also used when recording speech. When recording singing and music, the microphones are often further away from the sound source , which means that the entire body of the sound is recorded more completely and the surrounding space is also included in the recording more naturally as room sound . When recording noises for measurement purposes or for further use as samples, recording is also carried out from a distance, but if possible in an anechoic room.

Influencing factors

The sound technical success of a recording depends on the following factors:

  • the acoustic properties of the recording room, e.g. B. of its influence on reverberation and standing waves
  • the type and quality of the microphone, e.g. B. the directional characteristic and frequency response, impulse behavior, inherent noise and distortion factor
  • the positioning of the individual microphones to the sound source :
    • the position in the room or distance to the sound source
    • the angle between the plane radiating sound sources and the microphone
  • the positioning of several microphones in the ensemble (sound amplification, in the negative case also cancellation due to interference )
  • the type and level of mixing of the signal sources

The recording room can be acoustically optimized by suitable measures, e.g. B. by means of absorbers for damping, resonators or reflectors / diffusers for bundling or scattering. These can be movable or variable elements.

Stereo imaging of acoustic recordings with loudspeaker playback

Near level

Individual sound sources or groups of sound sources are displayed at a distance that is perceived as pleasant when listening directly, close behind the loudspeaker level.

  • Example: chamber music ensemble, individual instruments, singers and other soloists
  • Usual miking: The distance between the microphones and the sound body is significantly smaller than the reverberation radius of the recording room .

Middle level

Sound source groups are displayed behind the loudspeaker level at a distance appropriate to the group size. During playback, one has the impression of a comfortable listening distance.

The impression of distance resulting from the mixing is smaller than the reverberation radius of the room.

Further level

Level of a deep, large sound body. The acoustics of the recording room are clearly audible.

  • Example: wind instruments and possibly double basses, as well as the percussion instruments of a symphony orchestra and an organ in a large church.
  • Usual miking: Combination of main microphone arrangement and several support microphones.

Far away plane

Clearly placed sound sources that appear in the room or even outside the room, example: distant orchestra .

Critical parameters for sound recording

The success of a sound recording under - primarily - sound technical aspects of acoustic instruments (unplugged) depends on many factors, such as

  • the target format and the compatibility (mono, stereo, surround format)
  • of the type of musical style. Classical recordings by a chamber choir, for example, require different recording techniques than a rock production. The question of style is also decisive for the type of miking, because different styles have very different peculiarities of miking and in some cases deliberately violating the otherwise usual technical microphone placement rules.
  • on the acoustic properties of the recording room, e.g. B. the reverberation, the sound and the background noise.
  • the position of the instrument or instruments in space.
  • the position of the instruments in relation to one another if several instruments are recorded at the same time (e.g. crosstalk).
  • the placement of the microphones. The setup often influences the sound result in a more decisive way than the choice of the microphone itself (with the same directional characteristic). It is also a question of philosophy which sound result is desired. Here the choice of the plane (near, middle, far position) plays an equally decisive role (keyword: reverberation radius). In addition, there are unchangeable parameters (see first list) and the type of instrument. Some instruments require a certain distance in order to develop their tone (e.g. violin, accordion). The technical aspects of instrument construction must also be taken into account (e.g. bass drum without sound opening in the skin, guitar not removed at the pegs, the violin bow must not hinder the musician when playing with a microphone, etc.). In addition, reflections on the instrument and its surroundings lead to desired (denser sound) and undesired sound results (comb filter effect).
  • on the choice of microphones. Due to the different directional characteristics and frequency responses of the microphones, the frequencies emitted by the instrument and reflected by the room can be better or less well recorded depending on the microphone selection. The volume of an instrument can also be a more important factor, because otherwise it is possible that the microphone will be damaged if the dynamics are too high or the microphone will rustle if the volume of the instrument is too low.
  • the position of the microphone on the instrument or the voice. This is especially true for close-ups. Here, for example, the close-up effect of the voice plays a role. In the case of drums, for example, the sound is completely changed depending on the position (drum edge vs. middle of skin, removal from above / below, etc.). The instrument's own noises can also be decisive, e.g. B. damper noises (grand piano) or flap noises, with a hi-hat (drums) even a wrong position can completely destroy the microphone.
  • on the number of microphones and their position in relation to one another. When using several microphones, it is inevitable that frequencies will be canceled due to different transit times. Correct positioning or reducing the number of microphones can minimize the problem.
  • of upstream and downstream equipment. In general, you can already influence the admission procedure. If, for example, a strong compression is already used during the recording, you may have to set up a suitable microphone for this "sound".
  • of the experience of the musician or the musician with recordings. Experienced musicians work with the technique and know how to get the best result. For example, an experienced percussionist will use stereo microphones, and an experienced singer will use the close-up effect. Experienced musicians will also generally pay attention to dynamics and the problems associated with them.
  • from the experience of the sound engineer. For example, if a sound engineer knows the recording room well, the recordings are always better than if he does not know the recording room. Very experienced sound engineers can use their wealth of experience to assess unfamiliar rooms so well that they can also achieve very good recording results here. He usually has a certain number of microphones that he knows particularly well and prefers to use for certain applications.

Musical aspects can also make further adjustments necessary. This can certainly lead to poorer sound-technical results, but it can achieve better musical results - sound technology is not an end in itself, but has to be subject to the artistic requirements, which is why a purely technical setup alone cannot guarantee good recordings.

Technically speaking, every recording is different, musicians and instruments sound different every day, the sound engineer hears differently and the external conditions (temperature, air pressure, humidity or even power fluctuations in the network that affect the devices, etc.) are never the same. For example, no two pianists will play the same instrument alike.

Purely objective rules therefore do not exist at all, but have to be found each time individually for a good reception.

Microphone selection

Dynamic or condenser microphone?

Small diaphragm condenser microphones can have a very linear frequency response. In contrast, large-diaphragm condenser microphones or dynamic microphones have a less linear characteristic. In practice, a linear frequency response only plays an important role when recording classical music. With effect and pop music, the question of the individual sound character of a microphone type arises. You are looking for an effective special timbre.

In addition to aesthetic considerations, there are also tangible technical considerations. Dynamic microphones allow distortion-free recording even with significantly higher sound pressure levels than condenser microphones. In general, it can be said that condenser microphones are more likely to be used for concert recordings because of the better sound fidelity, while dynamic microphones are often preferred for concert acoustics, especially if other considerations are decisive (level stability, deliberate sound coloring, e.g. with vocal microphones, etc.). In the past, dynamic microphones were also considered to be more robust. There are now also condenser microphones, especially for the stage, which are no longer inferior to dynamic microphones in terms of robustness. The same goes for the feedback resistance. And high levels are no longer so problematic with modern condenser microphones.

Small and large diaphragm condenser microphone

Small diaphragm microphone

As a small diaphragm microphone apply to industry standard designation microphones whose microphone capsule a diaphragm diameter have less than 1 inch, corresponding to 2.54 cm. Typical small condenser microphones are 2.1 cm in diameter; Measurement microphones are also 1 ⁄ 2  inch (1.3 cm) and 1 ⁄ 4  inch (0.64 cm).

The capsule diameter significantly influences the sound and thus determines the intended use of the microphone. The smaller the capsule diameter, the higher the frequencies that can be correctly picked up and transmitted according to their direction of incidence and sound strength, since the microphone approaches the punctiform ideal and the effective membrane area is at most in the order of magnitude of the wavelength of the highest audible sound frequencies.

Small diaphragm microphones therefore have a fairly uniform course of sensitivity depending on the sound angle of incidence and transmit reasonably cleanly up to well over 15 kHz. In contrast, large diaphragm microphones z. B. to pronounced partial vibrations and interactions of the membrane with short-wave sound waves, so that in the upper frequency range from about 10 kHz an often non-uniform frequency curve occurs. The size and geometry of the entire microphone are also responsible for this. Small diaphragm microphones represent a small obstacle in the sound field and thus have less of a changing effect, e.g. B. is also very useful in stereo microphone arrangements when two microphones have to be placed in close proximity.

Basically, the smaller the capsule, the more neutral and precise the sound. This is why small diaphragm microphones are used almost exclusively in music productions and broadcasts where sound authenticity is important.

On the other hand, with smaller capsules one loses the capacitor area, whereby the sensitivity, i.e. the ability to convert a certain sound pressure into a voltage as high as possible, decreases and with fixed background noise of downstream amplifiers , the effective signal-to-noise ratio is worsened.

Due to their design, small-diaphragm microphones also have good backward attenuation , which is often required , i.e. the shadowing of sound waves coming from behind. Typical backward attenuation values ​​are up to 35 dB for cardioid small diaphragm microphones, while with large diaphragm microphones only a maximum of 20 dB attenuation from the rear is usual.

Large diaphragm microphone

Large diaphragm condenser microphone with microphone spider

In the case of condenser microphones, it is still customary in the industry to refer to capsules with diaphragm diameters greater than or equal to 1 inch = 2.54 cm as large diaphragm microphones , even if there are some young companies who do not take this definition, which has evolved over time, so seriously and even diaphragms with a diameter of only 0.75 inches = 1.9 cm (which are actually small diaphragm microphones) can be called large diaphragms in order to be able to market them better. The real thing is that the historically determined size of large diaphragm microphones still meets with a positive response from non-technical users and is therefore often a purchasing decision .

Small diaphragm microphones are preferred by some sound engineers as sensors that are less disturbing in the sound field due to their sound neutrality. Because of the specific sound of some large-diaphragm condenser microphones, other sound engineers still like to choose them precisely because of these properties. There are tube- type large-diaphragm condenser microphones from the brands AKG or Georg Neumann , which have been in use for decades and are used at very high prices.

The sound is significantly influenced by the capsule diameter and its interferences in the sound field and thus the intended use of the microphone is determined. The larger the capsule diameter, the more difficult it is for higher frequencies to be transmitted cleanly, since a membrane diameter of 2 cm and more is already in the order of magnitude of the wavelength of the still audible high sound waves, which leads to undesirable effects.

Another typical feature of large-diaphragm microphones is that they represent a large mechanical obstacle to the sound field and that the placement of such a large foreign body greatly distorts the sound situation in the immediate vicinity of the microphone. The often large-volume housing of large-diaphragm microphones also has an influence here.

Since the directional characteristic is very frequency-dependent and also less pronounced due to the large dimensions, this type of microphone typically produces a clearly audible sound color that is characteristic of each individual specimen, while small diaphragm microphones are much more similar in sound to one another.

Comparison between small and large diaphragm microphones

Large diaphragm microphones have a typical upper cut-off frequency of around 12 kHz, while small diaphragm microphones can transmit up to 40 kHz cleanly without any problems and can also follow impulses better. Modern large diaphragms consist of extremely thin (less than 2 µm) and light materials and can therefore reproduce high frequencies a little better than older models.

The smaller the microphone capsule, the more neutral and precise the sound. Large-diaphragm microphones are therefore often used in recording situations to color certain instruments or voices, e.g. B. to emphasize solo voices, especially vocals. For transmissions, however, where good backward attenuation values ​​of the microphones are important, large diaphragm microphones prove to be inferior: Typical values ​​for a cardioid large diaphragm microphone are 20 dB, while high attenuation of up to 35 dB is not uncommon for a small diaphragm microphone .

Large capsules have one advantage: the greater the capacitor area, the greater the sensitivity . With a given sound pressure, a large-diaphragm capsule therefore generates more signal voltage (modulation voltage), which improves the effective signal-to-noise ratio with the same background noise of subsequent electrical amplifiers . This means that microphones with lower noise can be built with large diaphragm capsules. Therefore, in the product range of some Far Eastern suppliers, there are visually impressive giant microphones with a relatively good signal-to-noise ratio.

small membrane large membrane
Self-noise higher lower
sensitivity lower higher
Sound pressure power higher less
Frequency range wider tighter
Sound field influence low strong
Dynamic range higher less

Remarks

In contrast to loudspeakers (which work deeply tuned), the size of the diaphragm does not play a role in the bass reproduction of (condenser) microphones, since the natural resonance of the transducer is essentially above the usable frequency range anyway.
Colloquially, it is often said that with a microphone the sound decreases . A microphone, however, is a sound pick-up because it is located in the sound field and picks up the acting sound there as a sensitive sensor . See on the other hand: Pickups for non-acoustic musical instruments. The "decrease" of structure-borne noise is part of the jargon of PA sound reinforcement.

See also

literature

  • Carlos Albrecht: The sound engineer: miking acoustic instruments in pop music . Schiele & Schoen Verlag, Berlin 2010, ISBN 3-7949-0806-6 , ISBN 978-3-7949-0806-6
  • Thomas Görne: Microphones in theory and practice. 8th edition. Elektor-Verlag, Aachen 2007, ISBN 978-3-89576-189-8
  • Norbert Pawera: Microphone Practice . 4th edition. Franzis Verlag, Munich 1993, ISBN 3-932275-54-3
  • Siegfried Wirsum: Practical sound technology, device concepts, installation, optimization. 1st edition. Franzis Verlag, Munich 1991, ISBN 3-7723-5862-4
  • Michael Ebner: Manual of PA technology. 1st edition. Elektor-Verlag, Aachen 2002, ISBN 3-89576-114-1

Web links