All microphones respond to vibrations (sound waves/acoustical energy) in the air that they convert into electrical energy (the audio signal) to be amplified. They are a ‘transducer’ - a device which converts energy from one form to another.
There are different types of microphone and they all convert these vibrations in different ways by using a diaphragm - This is a thin piece of material (such as paper, plastic or aluminium) which vibrates when it is struck by sound waves.
Other components, such as the magnet, vibrate when the diaphragm does, this is when the vibrations are converted to electrical signals.
Microphones generate a small electrical current referred to as 'Mic level', this signal is usually measured in millivolts. Before the signal can be used, it needs to be amplified to ‘Line level’ (0.5-2V)
Once the mic is brought up to line level, (through a pre-amp, usually on each mixer channel ((see mixing desk post!)) or separate pre-amp) the audio signal is fed to a power amplifier - a specialised amp which boosts the signal enough to be fed to loudspeakers.
Loudspeakers also act as a transducer, converting the electrical energy back into acoustical.
Dynamic Microphones
Dynamic (moving coil) microphones are versatile and ideal for general-purpose use. They have a simple design, are relatively sturdy and resilient to rough handling. They are also better suited to handling high volume levels from certain musical instruments or amplifiers. They have no internal amplifier and do not require batteries or external power.
'Ribbon' mics are also dynamic, with signal being generated in the same way. A large amount of ribbon designs feature an open air design so they naturally bi-directional and have a figure-of-8 response.
They are ‘sonically dark’ as the lower frequencies affect ribbon mics more than high frequencies, resulting in a smooth rolloff with decreased output at high frequencies. This means that ribbon mics can smooth harsh signals in a musical way, making them suitable for overly harsh bowed-strings/brass and some vocals (backing). Unlike moving coil's, Ribbon mics can't handle the high SPL due to the sensitivity of the ribbon at 0.6 - 4 microns thick (a human hair is 100 microns thick!)
Some pros of dynamic mics are:
-Inexpensive
-Hard-wearing, tough! Means you can mic drop with no problems!
-Built to tolerate high SPL (sound pressure levels) meaning they’re great for loud signals (drums, close mic’d guitar amps, vocals etc)
-Require no power to operate
-Versatile
Cons:
-Limited frequency response - ineffective over 16kHz (down to mass of the coil attached to the diaphragm, inertia causes high end response to roll off)
-Needs more amplification than capacitor mics - meaning more noise when working or more distant sound sources
Some of my favourites/the best dynamics available are:
-Shure SM57: Extremely durable and versatile, industry standard for snare drums & more
-Shure SM58: One of the most (if not the most) popular vocal mics
-Shure SM7B: Specifically tailored for vocals with bass roll-off, mid range presence boost & in-built pop shield (dynamic). Used to record Michael Jackson’s vocals for Thriller.
-Electrovoice RE20: Industry standard for broadcasting, the built-in pop shield negates sibilance and popping. Also immune to proximity effect bass boost. Maintains consistent frequency response at all angles. This is my fav (also Stevie Wonder's mic of choice)
-Sennheiser MD 421 II: Most versatile on the list, 5 position bass roll off means it sounds good on virtually anything! (and looks like a ray-gun, big win)
Condenser Microphones
These mics are built of 2 conductive plates separated by insulated material or air. One plate is fixed whilst the other (thin, metalised diaphragm) is made from ‘mylar’ and coated with gold to make it conductive. This thin plate moves in response to sound and as it vibrates from sound waves (like our ears do). It’s distance from the fixed plate varies, changing the voltage across the two.
Condenser (or Capacitor) mics exploit a basic law of physics which holds that if you vary the distance between the plates of a capacitor while an electrical charge is applied, the voltage between the two plates also changes.
To read the change in voltage without draining the charge, condensers require pre-amp with a high input impedance (this is why they include active circuitry).
Non Valve models (such as FETs, Field Effect Transistor) charge is derived from Phantom Power (+48v - Turn on/off before plugging or unplugging mic, otherwise it go bang).
Valve models feature external power supplies, providing necessary capsule for polarising voltage. Whilst more expensive, Valve models produce a warm, musical tonality and can be flattering for vocals!
Okay, so what can they do? How are they different from Dynamics?
Condensers can feature all types of polar patterns, with mics such as the AKG C414 allowing for the selection of polar patterns (We'll cover these soon). This, coupled with how they cover the whole frequency spectrum makes them extremely versatile. Condensers are sensitive, they can't handle the high SPL that dynamics can. Great for recording room sounds, not so much when close to loud sources.
Pros:
-Low mass from thin diaphragm means capacitors can cope with rapid changes in air pressure, especially at high frequencies. This means they can cover the whole frequency spectrum (20Hz to 20kHz)
-This makes them ideal for capturing instruments and vocals with important high-end (acoustic guitars, harps etc)
-On board circuitry means less noise
-Can be manufactured with any polar pattern, allows for versatility in uses, mic placement and techniques
Cons:
-Un-useable in humid environments, leads to a loss in sensitivity (can be dried out though)
-Can be extremely expensive (See Neumann U47 lmao)
Some of my favourites/the best dynamics available are:
-Neumann TLM-103: Amazing all rounder- one of my faves for recording vocals
-Rode K1: Kevin Parker's (Tame Impala) mono overhead when recording drums. A Valve mic that can record the whole kit on it's own just fine, i've tried. One of the best for money, if there's one mic i'd want to own, it's this.
-AKG C414: Most versatile on the list- with a ridiculous amount of Polar Patterns, a pair of these will mean you're equipped for anything.
-Neumann U47/67/87: Just... the best really- Made in Germany, there's no better quality
-Rode NT1: Most affordable on the list, incredible value for money & perfect for recording vocals/instruments at home or in a small studio. Definitely worth having regardless of your collection
Polar Patterns
The way a mic responds to sound arriving depends on its ‘polar pattern’
Polar patterns can be placed into 3 main groups:
Omnidirectional:
Captures sound evenly from all directions. Mechanically very simple, they respond to changes in air pressure and can be known as a ‘pressure mic’. They don’t exhibit any proximity effect (bass frequencies get's louder the closer you get) so their tonal balance is independent of distance to the sound source.
Cardioid/Unidirectional:
Referring to the shape of the polar pattern, they are sensitive to sounds arriving directly in front with the rear of a cardioid mic insensitive to sound.
The result of a Omni & Figure-of-8 combination, cardioids can be used when unwanted off-axis sound needs to minimised (room reverb, instrument spill) or for semi-isolating an instrument (snare drum).
Figure-Of-8/Bi-directional:
Capturing sound to both the front and rear & completely rejecting all sound to the side, Figure of 8 patterns are commonly found on Ribbon mics (due to the build of them). Essential in stereo recording techniques such as Blumlein & Mid/Side.
On-axis is where the sounds arrive at the diaphragm that's pointing completely towards the sound source.
Off-axis is where the mic is pointing away from the source & 90 degrees off-axis has the mic sit perpendicular to the sound source. 180 degrees off-axis points directly away from
the sound source.
Omnidirectional: Captures sound evenly from all directions.
Mechanically very simple, they respond to changes in air pressure
and can be known as a ‘pressure mic’. They don’t exhibit any
proximity effect so their tonal balance is independent of distance to
the sound source.
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