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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
hypercardioid - sensitivity
approx 12 dB less sensitive from sides two null points at +/- 110 degress off-axis
26
supercardioid - sensitivity
approx 9 dB less sensitive from sides two null points (least pickup) at +/- 125 degress off axis
27
bidirectional/fig-8 - sensitivity
most sensitive from front and back rejects sound at sides
28
condenser mics - sound and application
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
what microphones generally have a proximity effect?
microphones with directional polar patters
30
dynamic mics - sound and application
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
ribbon mic - sound and application
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
tube/valve mic - sound and application
warm coloured, lots of even harmonics fragile usually have their own power supply and thus do not need phantom good for vocals
33
DEF: frequency response
the lowest and highest frequencies that the mic can pick up well
34
cardioid - pickup pattern
picks up best in front of the mic partly rejects sounds approaching sides or rear of mic rejects sound best toward the rear
35
supercardioid - pickup pattern
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
hypercardioid - pickup pattern
picks up best in front partly rejects sounds approaching sides and rear 'tighter' more narrow pickup than supercardoid
37
omni - pickup pattern
picks up equally wel in all directions has no proximity effect
38
figure-of-eight - pickup pattern
picks up best in front and behind the mic rejects sounds to the sides
39
DEF: impedance
the mics effective output resistance at 1kHz
40
what is considered low, medium and high impedance for microphones?
low: 150-600 ohms med: 1000 - 4000 ohms high: above 25 kilohms
41
do you want the impedance of a mic to be low, medium, or high? why?
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
DEF: self-noise
a measure of how noisy a mic is
43
what is considered a good, very good, or great self-noise spec for a mic?
good: 25 dBA very good: 20 dBA excellent: 15 dBA
44
What is considered a very good self-noise spec for a mic mounted directly on an instrument?
30 dBA
45
how much power is supplied by phantom power?
12-48 volts DC
46
DEF: side-address
the mic picks up best from it's side you aim the side of the mic at the sound source
47
what is considered a good, very good, or excellent signal to noise ratio in a mic?
good: 69 dB very good: 74 dB excellent: 79 dB or higher
48
what is considered a very good signal to noise ratio if the mic is mounted on the instrument? why?
64 dB b/c the instrument's signal is so much louder than the mic's noise
49
DEF: end-address
the mic picks up best from it's end you aim the end of the mic at the sound source
50
what does a mic's sensitivity spec tell you?
how much output voltage a mic produces when driven by a certain SPL
51
high sensitivity mic vs. low sensitivity mic which puts out a stronger signal when both are exposed to equally loud sound?
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
What is a typical sensitivity spec for a condenser mic?
5.6mV/Pa (high sensitivity)
53
typical sensitivity spec for a dynamic mic?
1.8 mV/PA (medium sensitivity)
54
typical sensitivity spec for a ribbon or small dynamic mic?
1.1 mV/Pa (low sensitivity)
55
proper wiring to make sure mic cables do not reverse polarity
pin 1 shield, pin 2 white, pin 3 black or pin 1 shield, pin 2 red, pin 3 white or black
56
two types of mic preams
tube solid state
57
advantages of tube preamps
adds warmth and fullness distorts more musically -- produces even-order harmonics when driven adds a natural sounding, musical compression
58
advantages of solid-state preamps
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
why use a preamp with a transformer
more true-to-life less noisy and produces less hum when connected to other gear compared to transformerless designs
60
impedance optimal ratios mic : pre
5 : 1 10 : 1 - ideal
61
increasing impedance from low to high (if impedance is variable) gives what results?
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
benefits of large diaphragm mics
captures more acoustic energy and generates a higher signal voltage meaning larger diaphragm mics generally have lower self-noise than small diaphragm
63
benefits of small diaphragm condensers
great transient response - small diaphragm can follow sound waves more accurately extended high frequency response very consistent pickup pattern
64
large diaphram - applications
vocals and spoken word solo instruments you want to appear rich and vibrant
65
small diaphragm - applications
piano, acoustic guitar, other stringed instruments drums (OH, snare, hh, cymbals) and perc
66
how does a pzm/boundary mic work
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
should you filter mics before or after EQ
before
68
without eq how can you change the tone of a mic
position it off axis
69

Term 2 Theory Prep (11 decks)

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