What are microphones?
A microphone is a devise used for converting sound waves into electrical energy.
The main purpose is to record or amplify a sound source.
Name 4 the different types of microphones
- Dynamic
- Condenser (Capacitor)
- Ribbon
- Boundary
How does a Dynamic microphone work?
There is a diaphragm and coil in the microphone. The diaphragm moves backwards and forwards through the coil. The force of the magnetic field induced an electric current in the wire.
What are the pros and cons of Dynamic microphones?
Pros
- robust
- don’t require phantom power
- cheaper
- good for high volume levels
Cons
- will only work effectively up to 16kHz
- small sound output so lots of amplification needed
- poor transient response
- have to be close to the mic
How does a Condenser microphone work?
A condenser microphone has two plates that vibrate to create a signal. The diaphragm moves backwards and forwards which generates a current. You need a voltage goof through the condenser for this to work. You can either have a battery inside the mic or use an external 48volts of phantom power.
What are the pros and cons of a Condenser microphone?
Pros
- very light in weight
- good at picking up high frequencies
- can make virtually any sound polar pattern
- high output levels so less amplification needed
Sensitive with good transient response
Cons
- very fragile
- can be expensive
- needs phantom power to work
- loses sensitivity is used in a humid environment
How does a Boundary microphone work?
These work the same as Capacitor microphones, but contain a pressure capsule which detects the small changes in air pressure as sound travels around the room.
What is a Boundary microphone?
Boundary microphones are designed to be used at a boundary of a room (e.g. wall or floor). These microphones consist of a flat plate which picks up sound waves as they reflect and bound off the boundary plate.
What are the Pros and Cons of Boundary microphones?
Pros
- direct and reflected sounds arrive at the microphone at the same time which makes it more responsive
- can pick up higher frequencies than the human ear can hear
- high out levels so less amplification needed
- detailed, clear sound and good at high-frequency pick-up
- sensitive with good transient response l
Cons
- can be expensive
- loses sensitivity in a humid environment
- not robust, can be easily damaged
- needs 48v phantom power to work
How does a ribbon microphone work?
Ribbon microphones consist of a thin metallic strip of foil, suspended in front of a magnetic plate. Sound waves make the foil to vibrate, producing fluctuations in the electrical current, creating the audio signal.
What are the Pros and Cons of Ribbon microphones?
Pros
- produces warm and rich representation of the original sound
- it picks up a wide range of frequencies (beyond the human hearing)
- high output levels so less amplification needed
- extremely sensitive with good transient response
Cons
- it’s very sensitive therefore could be easily damaged
- not portable
- can be very expensive
- needs 48v phantom power
What are the four possible polar patterns?
- Cardioid
- Figure of 8
- Hyper-cardioid
- Omni Directional
Cardioid
Picks up the sound from the front axis of the microphone
Hyper Cardioid
It is even more frontward’s directional pattern with minor rear spill
Figure of 8
It picks up sound equally from both the front and the rear of the microphone
Omni Directional
Picks up sound equally from all sides of the microphone
Name 4 considerations when setting up the microphones
- The proximity effect
- Room ambience/reflections
- Noise reduction and room treatment
- Spill from other instruments
Close Microphone Technique
This is when the microphone is very close to the source and it captures the full colour and sound.
AB Stereo Pair / Spaced Pair
An exact pair of microphones spaced at a minimum of 1m away from the sound source.
Coincident Pair or XY Pair
Two microphones positioned with a 90 degree angle on top of each other. The centre of the two microphones should be aligned with the sound source.
Blumlein Stereo Pair
This is essentially the same as the XY Pair but with two figure of 8 polar patterns, instead of two cardioids.
Mid-side Stereo Pair
Two microphones, the front is a cardioid and the side microphone is Figure of 8. These microphones are placed on top of each other. The Figure of 8 is duplicated and panned R/L, one of which should be reverse phased, and the Cardioid is panned in the centre.
