microphones Flashcards
What is a moving coil mic called
Dynamic microphone
Explain Electromagnetic Induction
A moving coil is positioned in a magnetic field, attached to a diaphragm. The diaphragm vibrates in equal response to sound/air pressure. The coil moves in the magnetic field to create an electrical current that is proportional to the changes in air pressure.
How does a condenser mic function
Contains capacitor which consists of two plates. Sound causes one of the plates to vibrate, which functions as a diaphragm, and that gap between the two plates changes. The plates are powered, therefore moving the diaphragm causes a change in capacitance, and a current flows
Features of a Dynamic mic
Robust
Can withstand High SPL
Good for live use
Does not require Phantom power
Limited high frequency response- Suitable for bass instruments
Features of a Condenser mic
Sensitive, giving effective capture of quiet sounds
Flat and accurate frequency responses
Able to capture a wide frequency range
Can capture a brighter signal
Good signal-to-noise ratio- High output volume and thus low noise
wide dynamic range
Suitable for most studio work
How does a Ribbon mic function
Sound vibrations disturb metallic ribbon suspended in a magnetic field, which generates a voltage that is proportional to the movement of the ribbon. ‘Warm’ sound when used as a close mic with emphasised low frequencies. Is damaged by Phantom power
Fragile and very Expensive
What is a pre-amp
It coverts a signal into a workable Line Level
Phantom Power
48v from a mixing desk or an audio interface to provide power for condenser microphones and DI boxes
Gain
The amount of boost applied to the pre-amp stage of an audio channel. Used either to boost signals to an operable level or to boost beyond that point to drive a signal into distortion for musical purposes
Pad
A switch on equipment that attenuates the gain by a set amount to prevent clipping
High Pass Filter
A type of filter that removes only lower frequencies below a set cut off frequency and allows high frequencies through unaffected. Sometimes known as a ‘Rumble Filter’
Polarity
Inverts the polarity of the signal
Clip/Activity LEDs
These will illuminate when a signal is clipping/distorting, and when a signal is going through the channel
Polar Patterns
A microphones polar pattern describes how it picks up sound from all around the capsule
Omnidirectional
Picks up sound from all around the capsule
Captures room ambience
Provides little isolation so can lead to spill being captured
Useful if the space sounds nice or the instrumentalists are all around the microphone
Cardioid
Rejects sound from behind the microphone
Minimises the amount of reverb and/or noise from behind the microphone that is captured
Used for most close-mic work
Hypercardioid
Picks up sound from in front of the capsule and gives some capture of those behind
Effective at providing partial isolation from other instruments but capturing some of the ambience of the room
Figure-of-8
Picks up sound from in front of and behind the capsule
They are used in M/S (mid-side) recording techniques to give a stereo image of the sound
Figure-of-8 microphones strongly reject sound from the sides of the capsule
How can you avoid capturing Unwanted noise and spill
Performers wear Close-back Headphones
Keeping monitor mix relatively quiet in Headphones
Using acoustic screens/isolated booths
Making use of overdubbing and directional microphones
What is frequency response
A mics frequency response shows what frequencies it picks up, commonly displayed in a graph.
The flatter the graph, the more ‘true’ the sound is- any peaks means that those frequencies are captured louder than they are in ‘real-life’
What is Transient response
How quickly the diaphragm can move when disturbed by a vibration
Transient response in reference to Condenser mics
Has a small diaphragm so tends to have a faster Transient response, as the diaphragm is light and easy to move
This means their high frequency response is often better
Transient response in reference to Dynamic mics
Diaphragm is connected to a heavy coil, so does not move as quickly.
Can introduce a form of acoustic compression
What does gain do
Changes the level of gain to aim to minimise noise and unwanted distortion
