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Term 2 Theory Prep > Microphones > Flashcards

Microphones Flashcards

1
Q

how does a dynamic mic work

A

works via electromagnetic induction. A cone is attached to a coil of wire which moves in the field of a magnet. When the diaphragm vibrates, the coil moves in the magnetic field, producing changes in current that directly relate to the changes in air pressure.

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2
Q

how does a ribbon mic work

A

works via electromagnetic induction. When the long thin strip of conductive foil moves within the magnetic field it generates a voltage that directly relates to the changes in air pressure

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3
Q

how does a condenser mic work

A

diaphragm acts as one plate of a capacitor, and the vibrations produce changes in the distance between the plates and therefore a change in electrical energy

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4
Q

what are the two types of condenser mics

A

true condensers and electrets

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5
Q

what’s the difference between a true condenser and an electret

A

true condenser needs power to charge the back-plate of the diaphragm. electret has an already-charged back-plate that remains charged for the life of the mic however, both still need voltage to run

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6
Q

what are the three main types of transducers

A

1) electro-dynamic / dynamic (moving coil, ribbon and printed ribbon) 2) condenser (incl. electret, PZM/boundary) 3) piezo or crystal-based

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7
Q

dynamic moving coil mics - transient response & sensitivity

A

slower transient response and lower sensitivity to small pressure variations because of relatively heavy moving parts

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8
Q

dynamic ribbon mics - transient response & sensitivity

A

sensitive to small variations in pressure due to light moving parts, give more accurate transient response than moving coil mics

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9
Q

dynamic moving coil - transparency

A

genrally add colour in the high mids (5-10kHz)

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10
Q

dynamic moving coil - durability

A

generally very durable, can handle high SPL

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11
Q

dynamic ribbon - transparency

A

generally add colour, high frequency roll-off, proximity effect

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12
Q

DEF: proximity effect

A

a directional mic’s increase in bass response as the sound source approaches the diaphragm

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13
Q

dynamic ribbon - durability

A

fragile

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14
Q

PZM (boundary) mics - transparency & amp sensitivity

A

do not have off-axis colouration, present even frequency response and high sensitivity, you also get less of the room tone

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15
Q

printed ribbon mics - durability

A

more durable than traditional ribbon mics

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16
Q

printed ribbon mics - transient response

A

good transient response due to light moving parts

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17
Q

DEF: comb-filtering

A

comb-filtering creates peaks and troughs in frequency response, and is caused when signals that are identical but have phase differences

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18
Q

identify this polar pattern

A

omnidirectional

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19
Q

identify this polar pattern

A

subcardioid

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20
Q

identify this polar pattern

A

cardioid

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21
Q

identify this polar pattern

A

supercardioid

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22
Q

identify this polar pattern

A

hypercardioid

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23
Q

identify this polar pattern

A

figure-of-eight (bidirectinal)

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24
Q

cardioid - sensitivity

A

approx 6 dB less sensitive to from sides

approx 15-25 dB less sensitive from rear

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25
Q

hypercardioid - sensitivity

A

approx 12 dB less sensitive from sides

two null points at +/- 110 degress off-axis

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26
Q

supercardioid - sensitivity

A

approx 9 dB less sensitive from sides

two null points (least pickup) at +/- 125 degress off axis

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27
Q

bidirectional/fig-8 - sensitivity

A

most sensitive from front and back

rejects sound at sides

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28
Q

condenser mics - sound and application

A

high-fidenilty, detailed sound with lots of clean high frequencies.

very sensitive due to thin diaphragm

good for high top end content, acoustic guitars and voices

Require phantom power

29
Q

what microphones generally have a proximity effect?

A

microphones with directional polar patters

30
Q

dynamic mics - sound and application

A

edgy high frequencies

presence peak 2-5 kHz

lack of air in top end

slower response

good for close mic’d sources, percussive sounds, heavy bass/midrange content and live vocals

do not need phantom power

31
Q

ribbon mic - sound and application

A

warm, smooth sound quality.

top end roll off at ~10 kHz

sounds darker

fragile

popular for horns and guitar amps.

does not require phantom power

32
Q

tube/valve mic - sound and application

A

warm coloured, lots of even harmonics

fragile

usually have their own power supply and thus do not need phantom

good for vocals

33
Q

DEF:

frequency response

A

the lowest and highest frequencies that the mic can pick up well

34
Q

cardioid - pickup pattern

A

picks up best in front of the mic

partly rejects sounds approaching sides or rear of mic

rejects sound best toward the rear

35
Q

supercardioid - pickup pattern

A

picks up best in front of the mic

partly rejects sound approaching the sides or the rear

‘tighter’ or more narrow pickup than cardoid

has small pickup area in the rear of mic

36
Q

hypercardioid - pickup pattern

A

picks up best in front

partly rejects sounds approaching sides and rear

‘tighter’ more narrow pickup than supercardoid

37
Q

omni - pickup pattern

A

picks up equally wel in all directions

has no proximity effect

38
Q

figure-of-eight - pickup pattern

A

picks up best in front and behind the mic

rejects sounds to the sides

39
Q

DEF:

impedance

A

the mics effective output resistance at 1kHz

40
Q

what is considered low, medium and high impedance for microphones?

A

low: 150-600 ohms
med: 1000 - 4000 ohms
high: above 25 kilohms

41
Q

do you want the impedance of a mic to be low, medium, or high?

why?

A

low impedance

the higher the impedance of a mic the more likely you are to pick up hum or lose high frequencies when the signal runs through cables

42
Q

DEF:

self-noise

A

a measure of how noisy a mic is

43
Q

what is considered a good, very good, or great self-noise spec for a mic?

A

good: 25 dBA

very good: 20 dBA

excellent: 15 dBA

44
Q

What is considered a very good self-noise spec for a mic mounted directly on an instrument?

A

30 dBA

45
Q

how much power is supplied by phantom power?

A

12-48 volts DC

46
Q

DEF:

side-address

A

the mic picks up best from it’s side

you aim the side of the mic at the sound source

47
Q

what is considered a good, very good, or excellent signal to noise ratio in a mic?

A

good: 69 dB

very good: 74 dB

excellent: 79 dB or higher

48
Q

what is considered a very good signal to noise ratio if the mic is mounted on the instrument?

why?

A

64 dB

b/c the instrument’s signal is so much louder than the mic’s noise

49
Q

DEF:

end-address

A

the mic picks up best from it’s end

you aim the end of the mic at the sound source

50
Q

what does a mic’s sensitivity spec tell you?

A

how much output voltage a mic produces when driven by a certain SPL

51
Q

high sensitivity mic vs. low sensitivity mic

which puts out a stronger signal when both are exposed to equally loud sound?

A

high sensitivity mic puts out a stronger signal than a low sensitivity mic

low sensitivity mic will need more gain from mixer which usually results in more noise

52
Q

What is a typical sensitivity spec for a condenser mic?

A

5.6mV/Pa (high sensitivity)

53
Q

typical sensitivity spec for a dynamic mic?

A

1.8 mV/PA (medium sensitivity)

54
Q

typical sensitivity spec for a ribbon or small dynamic mic?

A

1.1 mV/Pa (low sensitivity)

55
Q

proper wiring to make sure mic cables do not reverse polarity

A

pin 1 shield, pin 2 white, pin 3 black

or

pin 1 shield, pin 2 red, pin 3 white or black

56
Q

two types of mic preams

A

tube

solid state

57
Q

advantages of tube preamps

A

adds warmth and fullness

distorts more musically – produces even-order harmonics

when driven adds a natural sounding, musical compression

58
Q

advantages of solid-state preamps

A

less distortion until they reach clipping point – great for adding clear gain

quicker transient response and retain more high frequency information (great for transient instruments)

generally more efficient, produce less heat and require less maintenance than tubes

59
Q

why use a preamp with a transformer

A

more true-to-life

less noisy and produces less hum when connected to other gear compared to transformerless designs

60
Q

impedance optimal ratios

mic : pre

A

5 : 1

10 : 1 - ideal

61
Q

increasing impedance from low to high (if impedance is variable) gives what results?

A

increase in volume as you get higher

less dark and mid-heavy tone, more airy high frequency content

potentially more room tone

appears to flatten out mic’s frequency response

62
Q

benefits of large diaphragm mics

A

captures more acoustic energy and generates a higher signal voltage

meaning

larger diaphragm mics generally have lower self-noise than small diaphragm

63
Q

benefits of small diaphragm condensers

A

great transient response - small diaphragm can follow sound waves more accurately

extended high frequency response

very consistent pickup pattern

64
Q

large diaphram - applications

A

vocals and spoken word

solo instruments you want to appear rich and vibrant

65
Q

small diaphragm - applications

A

piano, acoustic guitar, other stringed instruments

drums (OH, snare, hh, cymbals) and perc

66
Q

how does a pzm/boundary mic work

A

condenser mic mounted facing a metal plate

works by using the phenomenon that occurs near a reflection point, the sound signal and reflection combine to create comb filtering, which creates peaks and valleys in the frequency response

67
Q

should you filter mics before or after EQ

A

before

68
Q

without eq how can you change the tone of a mic

A

position it off axis

69
Q
A

Term 2 Theory Prep (11 decks)

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