Microphone types and specific microphone techniques

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Microphone types and specific microphone techniques Dimitrios Mylis

The first microphone (mic) was known as Carbon, and it was invented in 1877 by David Edward

Hughes (Hughes, 2007, Concertinist and Inventor). This microphone had pieces of loosely

packed carbon grains and it was very similar to the one used in the present day. Microphones

were first used in telephones and assisted on the development of broadcasting and recordings

(Columbia Electronic Encyclopedia, 2013, p1). Between numerous microphone types, there are

three that should be mentioned because of their characteristics; Condenser or Capacitor mic,

Dynamic mic and Ribbon mic (Shure, n.d, Microphones Transducer Types).

In 1916, E. C. Wente invented the Condenser mic, which is also known as Electrostatic

microphone. This device converts the acoustic energy into electrical energy through a

transducer, resulting in the creation of electric signals, which drive the sound information to the

end of the cable (Hughes, 2007, Concertinist and Inventor). Condenser mics have two ways in

order to extract sound signals, known as DC biased and radio frequency (RF). In the DC biased

method, the voltage variations in the capsule are further amplified because it passes through a

resistor but the charge within the capsule remains constant. On the other hand in RF method,

sometimes the capsule modulates the frequency of the output, but sometimes the change of the

capacitance, modulates the amplitude of the output (Engineers, Condenser Microphone).

Condenser mics can pick up high frequencies and quiet sounds, because of the thin diagrams.

Moreover, condenser mics produce a high quality audio, have a faster/flatter frequency

response and are more sensitive to sound, typically in the region of 3 to 20 mV/Pa., unless they

are the RF type, because of the pad switch that they have (Mascrey, 2006, Introduction).

Counter to the condenser mic, in a dynamic mic, the vibrations of the diaphragm convert the

sound to an electrical signal, resulting to the vibration of a coil on a very small scale. Typically,

the sensitive region of low impedance dynamic mic is around 1 to 3 mV/Pa (Paformusic, n.d,

Microphones). The dynamic microphones are suitable for small distance recordings and they

have no need of an amplifier or batteries. On the other hand, the dynamic mics cannot pick up

high frequencies that well, because of the thick diaphragm that is attached to a wire coil

(Mascrey, 2006, Introduction). Ribbon mic belongs to the "family'' of dynamic microphones.

Between of the magnet poles of the Ribbon mic, there is a thin electrical ribbon, which is

typically bidirectional. Furthermore, Ribbon mics cannot pick up sounds from the side of the mic

but they pick up sounds from both the front and rear (Shure, n.d, Microphones Transducer).

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When choosing a microphone, an important aspect to consider is the polar patterns and the

frequency response of the mic. The level of the sensitivity of a mic, from the lowest to highest

frequency, is the frequency response. There are two kinds of frequency response: the flat (See

image 1, appendix 1) and the tailored (See image 2, appendix 1) frequency response (Shure,

n.d, Microphones Frequency). Flat frequency response is all the frequencies between 20 Hz

and 20 kHz and have the same output level. In contrast with the flat frequency response that

has designed in order to reproduce the original sound without any changes, the tailored

frequency response has designed to gain the sound (Prosoundweb, 2011, Microphone

Characteristics). The sensitivity to sound relative to the direction or angle from which the sound

arrive, is the polar pattern of a microphone, and the most common types are Omnidirectional

(See image 3, appendix 1), Cardioid (See image 4, appendix 1) and Supercardioid (See image

5, appendix 1) (Shure, n.d, Microphone Polar). Omnidirectional can pick up sound from every

side of the mic but its possible to cause feedback in many situations. In contrast, despite that

Cardioid mic are most sensitive on the front, they are more difficult to cause feedback, because

they isolate the unwanted sounds. Supercardioid are like Cardioids but they are better in the

rejection of unwanted sounds and for that reason they are more resistant to feedback (Mascrey,

2006, Polar).

(See image1, appendix 1)

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(See image 2, appendix 1)




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Humans use three specific methods in order to localize the sound, which are the Interaural

Intensity Differences (IID), the Interaural Timing Differences (ITD) and the Head Related

Transfer Function (HRTF). In the IDD method, humans can localize the sound by the difference

in loudness between the left and right ear. In ITD method, the localization of the sound is

achieved by the difference in timing between left and right ear and last in HRTF method,

humans can localize the direction of the sound by the tonal difference between the ears

(Thomson, n.d, Introduction to studio). According to Dr.Rosse these methods belong to the

Binaural cues (Ross, n.d., A place theory, p35-39). Furthermore, humans use three stereo

microphone techniques in order to record these sounds. Firstly, is the Coincident category type

where microphones are positioned close to each other. This category includes the X-Y pair type

(See image 6, appendix 1), the Blumen pair type (See image 7, appendix 1) and the Mid side

type (See image 8, appendix 1). In X-Y type, there is good mono compatibility and there are not

tonal problems because of the close proximity of the mics. It is possible to increase the angle

but 135° is the maximum, because going past that creates centre hole problems. (Thomson, n.d,

Introduction to studio). Additionally, there must be two Cardioid microphones of the same type,

in order to complete the X-Y technique (Shure, n.d, Microphone Stereo). The Blumen pair type

has good stereo imaging, but because of the Bi Directional polar patterns it is not so good in

some types of room. The Mid side type has good mono compatibility and good stereo imaging

too like the X-Y. Also there are two Near Coincident pair types, the Faulkner Array (See image 9,

appendix 1) and the Near Coincident pair (ORTF) (See image 10, appendix 1). Faulkner Array

type has two groups of eight mics pointing directly at the sound source and the Near Coincident

pair was invented in order to emulate the distance between left and right ear. Secondly, the

Spaced or A-B category type, where there is a distance between the two microphones. This

category includes the Spaced Cardioid (See image 11, appendix 1), the Spaced Omni (See

image 12, appendix 1) and Decca Tree (See image 13, appendix 1). Because of the

directionality of the cardioid patterns, the Spaced Cardioid type is really useful in a difficult

sounding space. Despite that the Spaced Omni works like Spaced Cardioid, has to be close to

the sound source and requires a good and quiet sounding place. Also, the Decca Tree style has

a good stereo image and produces a sound recording in a high quality. Thirdly, the Baffled

category type is where there mics are positioned either side of a diaphragm in order to emulate

the head. This category includes Jeklin Disk Technique (See image 14, appendix 1) and The

Wedge Technique (See image 15, appendix 1). The Jeklin Disk Technique is emulating the

separation between left and right ear by a coincident pair with a thick circular diaphragm. This is

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the AKA Oprimum stereo signal technique. The Wedge Technique has good mono compatibility,

good stereo image and is pretty similar to the Jeklin Disk, with the only difference being that it

uses a wedge diaphragm through PZM microphones on the surface (Thomson, n.d, Introduction

to studio).

Furthermore, there are specific microphone techniques in order to record a grand piano. The

quality and the "feeling" of a sound depend on the position of the microphone. In the following

image we can see the most known positions of a microphone in order to record a grand piano

(See image 16, appendix 1).

In the first position, the microphone is 12 inches above the middle strings and 8 inches

horizontally from hammers, resulting to a natural well-balanced sound. In the second position,

the microphone is 8 inches above the treble strings but it is not shown in the image above. This

gives the same results with the first position, but with a slightly brighter sound. In the third

position, the results are different. By positioning the microphone, in order to aim the sound holes,

the sound becomes thinner, duller, and harder. Moreover, in the fourth position, microphone is 6

inches over the middle strings and 8 inches from the hammers, resulting to a muddy and boomy

sound. In the fifth and sixth positions, despite that in the fifth position the microphone is next to

the underside of the lid and in the sixth position the microphone is underneath the piano, we

have as a result a bassy and full sound. Furthermore, in the seventh position, the microphone is

mounted on underside of lid and around of the treble strings, close to hammers for brighter

sound. This has as a result, a brighter and well-balanced sound. In the eighth position, there are

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two surface-mount microphones positioned under the edge of the closed lid, and at its keyboard

edge, resulting on, a bright, well balanced but strong sound. In the ninth and last position, the

microphone is placed vertically on the inside of the frame, near the apex of the piano’s curved

wall, giving an excellent isolation, and a natural, full sound (Shure, n.d, Microphone Positioning).




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APPENDIX

1: Images

Image 1 source: Shure Legendary Performance, n.d, Microphones Polar Patterns. Retrieved

from

http://www.shure.co.uk/support_download/educational_content/microphones-

basics/microphone_polar_patterns


from




from




from




from



Image 6 source: Thomson P., n.d, Introduction to studio techniques, Topic 2, Stereo

Microphones Powerpoint File. Retrieved from

http://moodle.port.ac.uk/course/view.php?id=264

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Image 8 source:Thomson P., n.d, Introduction to studio techniques, Topic 2, Stereo





















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Image 16 source: Shure Legendary Performance, n.d, Microphones Positioning Piano.

Retrieved from

http://www.shure.co.uk/support_download/educational_content/microphones-basics/piano

Image 17 source: Shure Legendary Performance, n.d, Microphones Positioning Piano.

Retrieved from


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2: Bibliography

Columbia Electronic Encyclopedia, 2013 September, 6th Edition, p1-1, 1p

Engineers Garage, n.d, Condenser Microphone. Retrieved from

http://www.engineersgarage.com/electronic-components/condenser-microphone-pinout

Hughes.D.E, 2007, Concertinist and Inventor". Retrieved from

http://www.angloconcertina.org/files/HughesforWebsite.pdf

Mascrey J. (2006), Burning Grooves, Introduction to dynamic and condenser microphones.

Retrieved from

http://www.burninggrooves.com/articles/introduction-to-dynamic-and-condenser-microphones

Mascrey J. (2006), Burning Grooves, Polar Patterns Explained. Retrieved from

http://www.burninggrooves.com/articles/polar-patterns-explained

Prosoundweb, (2011 May), Microphone Characteristics Vital To Know For Sound

Reinforcement. Retrieved from

http://www.prosoundweb.com/article/print/microphone_characteristics_for_live_sound_reinforce

ment

Paformusic, n.d, Microphones. Retrieved from

http://www.paformusic.info/mics.htm

Ross J, n.d., A place theory of sound localization. Journal of Comparative and Physiological

Psychology 41, p35-39

Shure Legendary Performance, n.d, Microphones Frequency Response. Retrieved from


basics/microphones_frequency_response

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Shure Legendary Performance, n.d, Microphones Polar Patterns. Retrieved from



Shure Legendary Performance, n.d, Microphones Positioning Piano. Retrieved from


Shure Legendary Performance, n.d, Microphones Stereo Microphones Techniques. Retrieved

from


basics/stereo_microphone_techniques

Shure Legendary Performance, n.d, Microphones Transducer Types. Retrieved from


basics/microphone_transducer_types

Thomson P., n.d, Introduction to studio techniques, Topic 2, Stereo Microphones Powerpoint

File. Retrieved from


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