Microphone Types

Question 1

What is a diaphragm?

Answer 1

A light and thin piece of material attached to a metal coil, which is placed inside a magnet.

Question 2

What happens as sound waves make the diaphragm vibrate?

Answer 2

The coil moves rapidly in the magnetic field. This makes electricity flow in the wires, producing a very small electrical signal.

Question 3

Describe how the plates work in a condenser microphones

Answer 3

• Two plates (very thin sheets of conducting material) are held a tiny distance apart.
• A standing electrical charge rapidly builds up between them when they are positive and negative.
• When the diaphragm plate vibrates, the charge is disturbed and electricity flows between the two.

Question 4

Describe the differences between cost in a Dynamic and Condenser microphone.

Answer 4

Dynamic - Less expensive and more easily available

Condenser - Genrally costs more than a dynamic microphone.

Question 5

Describe the differences between handling in a Dynamic and Condenser microphone.

Answer 5

Dynamic - Robustly made and can survive the occasional knock or drop.
Condenser - The mechanism is delicate and needs to be handled with care. Humidity and extreme cold need to be avoided too.

Question 6

Describe the differences between amplification in a Dynamic and Condenser microphone.

Answer 6

Dynamic - produces a very low level audio signal which needs lots of gain from a preamp before being useable.
Condenser - Needs pre-amplifying - but not as much as a dynamic microphone.

Question 7

Describe the differences between power in a Dynamic and Condenser microphone.

Answer 7

Dynamic - doesn’t need a power source as it makes its own.

Condenser - Needs power- some use a battery in the casing. Most need phantom power which is sent along signal wires.

Question 8

Describe the differences between placement in a Dynamic and Condenser microphone.

Answer 8

Dynamic - Used for close/loud sounds.

Condenser - Can be used close up but is also good for low level and distance sounds.

Question 9

Describe the differences between frequency in a Dynamic and Condenser microphone.

Answer 9

Dynamic - Less sensitive at high frequencies than a condenser.
Condenser - Has a very good frequency range, sometimes up to the limit of human hearing or beyond. this makes condenser mics the choice for high quality capture of complex, wide ranging sounds.

Question 10

Why do Condenser mics work better with high frequencies?

Answer 10

They use a smaller, lighter diaphragm to capture sound.

Question 11

Describe the uses of Dynamic mics and why.

Answer 11

Their strong construction makes dynamic mics suited to situations where there are high levels of sound:

• Kick drum
• Snare drum
• Toms
• Close mic trumpet, sax etc
• Guitar amp
• Live vocals

Question 12

Describe the uses of Condenser mics and why.

Answer 12

They need more careful handling and don’t always survive at high spl’s:

• Stereo or ambient recording
• Drum overheads
• Instrumental recording in more controlled conditions to capture full range of sound.
• Acoustic/classical guitar amplification and recording.
• Recording vocals, to capture the maximum frequency range and quality of sound.

Question 13

How does the diaphragm relate to polar patterns on a condenser?

Answer 13

For a microphone to have different polar patterns it must have more than one diaphragm element.

Question 14

How are polar patterns formed generally?

Answer 14

The electrical outputs from each of the diaphragm elements, which result from the impinging acoustical sound pressure levels, are added or subtracted from each other.

Question 15

What is a common way to create different polar patterns in one microphone?

Answer 15

Mount two condenser cardioid elements back to back inside the mic housing.

Question 16

What is a common construction method in creating a polar pattern mic?

Answer 16

Create a single element with two diaphragms (one facing the front of the mic, the other facing the rear) with a common backplate. The mic body is also designed with appropriate slits and internal acoustic delay elements as part of the cardioid design.

Question 17

What type of voltage do condenser polaroid mics require?

Answer 17

Polarising voltage.

Question 18

Describe the polarising voltage in the front and rear diaphragms.

Answer 18

The polarizing voltage to the front element is fixed, but the voltage to the rear element is variable. A common method is to switch this voltage, and that is what the selector on the mic body is doing.

Question 19

What is the diaphragms element sensitivity proportional to?

Answer 19

The applied polarising voltage.

Question 20

What produces the final output of the polaroid mic?

Answer 20

The electrical signal (AC) outputs of each diaphragm element summed together.

Question 21

Describe the voltage in a cardioid pattern?

Answer 21

If the switch is set to the cardioid position, the voltage to the rear diaphragm element is switched off, so that only the front element contributes any signal.

Question 22

What happens if the polar pattern switch is set to omni?

Answer 22

It switches in a DC polarizing voltage to the rear element that is equal in value and polarity as that of the front. Now, both elements will produce signals each with a cardioid polar pattern. When the two cardioid patterns are added together they produce an omnidirectional pattern.

Question 23

What happens if the polar pattern switch is set to figure-8 (bidirectional)

Answer 23

it switches in a DC polarizing voltage to the rear element that is equal in value but opposite in polarity to that of the front. This means that the signal from the rear cardioid element is subtracted from the signal from the front cardioid element, resulting in the figure-8 pattern.