Microphone types

There are basically 4 types of microphone. Each has its very peculiar characteristics, which are bound to the materials they are made with.
Dynamic microphones have a simple and comparatively sturdy construction. No power supply is required and they are relatively inexpensive.
Dynamic Microphone Example
In a dynamic microphone, sound waves cause a movable wire or coil to vibrate in a magnetic field and thus induce a current, to then be converted back to sound.
Cross-Section of Dynamic Microphone
Dynamic microphone are used almost for anything, but they are not always a wise choice. Their construction allows only close recording. If one is just a bit further, the recorded volume decreases exponentially. Therefore, it is the choice on stage, because it removes all the noisy background and is focused on the spot where it is placed. Its particular ruggedness allows it to withstand any sound pressure, included the loudest kick drums.
Heavy microphone diaphragm and wire coil limits the movement of the assembly, which in turn restricts the frequency and transient response of the microphone. Thus, it is not suitable for recording instruments with higher frequencies, such as a violin. For vocals, it convers a punchy, ample, round sound centered in the lower registry. Therefore, it imitates the historical microphones of the '60s, with which so many great voices have been recorded. The slow transient response causes the recording to be a bit delayed, and thus very round, masking the imperfections. It can make an untrained and shaky voice seem professional. However, due to the little sensitivity at increasing distances, it loses all the highs and the recording seems dinamically compressed - therefore unnatural. Because of this, professionals tend to use condenser microphones.
One big pro of dynamic microphones is their completely flat frequency response - except for some models that pump up the highs (see Shure). This makes for a faithful recording, were it not for the mentioned shortcomings.
Condenser microphones are less sturdy than their dynamic counterpart, but offer some unique characteristics. They are usually more expensive than any other type of microphone.
Capacitor Microphone Example
They use a pair of charged metal plates, one fixed (the back plate) and one movable (the diaphragm), forming a capacitor. When a sound wave hits the diaphragm, the distance between the two plates changes which produces a change in capacitance. The electrical signal corresponding to the sound picked up corresponds to the variation of the spacing, due to the motion of the diaphragm relative to the fixed back plate.
Cross-Section of Capacitor Microphone
Capacitor microphones are of two types: Small capsule and large capsule. The former ones display a flatter frequency response, while the latter ones have a very inconstant curve and need to be heavily corrected. Both types have an ecceptional sensitivity. They can easily pick the noise of a finger rubbing a sheet of paper fifty meters afar. However, small capsule microphones are more indicated for high frequencies, while the large capsule ones also have good basses.
Nowadays, capacitor microphones are basically the standard in professional recordings. There are models with an extra thin membrane, which can pick up even the details that escape ordinary hearing and have superior transient response. However, they suffer from their inconstant frequency response, as we said. Moreover, manufacturers tend to push the higher frequencies hard, in order to add a sort of "airiness" to the recordings, which further increases the issue.
Frequency Response Of A Condenser Microphone
The Telefunken 251 lacks basses up to 130 Hz. Then, it has a continuous swing of around 3 dB. If we consider that 3 dB means that the volume doubles, we can see at once that this microphone will give erratic results. From 3 kHz to 15 KHz, the highs skyrocket up to 6 dB, which means thrice the volume of lower frequencies.
Each condenser microphone displays its peculiar curve. However, in general we always find the issue with non existent basses and pumped up highs. The unequal response makes it so that musicians line up in the stores to try as many microphones as they can find. Recording becomes a matter of taste - i.e. what sounds better with a certain instrument, voice, context. However, we have to bear in mind that these microphones do not record reality faithfully, but they distort it. It would be much wiser to have a faithful representation and then apply EQ as we want, with full control on the process, instead of working with a defective recording from start. Therefore, we always need to check the specs to find out how faithful a condenser microphone is.
Electret microphones are a type of electrostatic capacitor-based microphone, which eliminates the need for a polarizing power supply by using a permanently charged material. They employ small capsules. Nowadays, they are not often used. However, they display a quite flat frequency response, making them very desiderable as a rugged general use microphone.
Cross-Section of Electret Microphone
Frequency Response Of An Electret Microphone
Ribbon microphones are also known as a ribbon velocity microphones. They use a thin aluminum, duraluminum, or nanofilm of electrically conductive ribbon placed between the poles of a magnet to produce a voltage by electromagnetic induction. Ribbon microphones are typically bidirectional, meaning that they pick up sounds equally well from either side of the microphone.
Ribbon Microphone Example
They were very common in the past, before condenser microphones. However, at the time it was very tricky to make powerful magnets - neodynium magnets still did not exist. Therefore, they were very bulky and heavy. Modern versions are much lighter, powerful, and responsive. Therefore, they are gaining momentum in the industry.
Ribbon microphones can be thought as something intermediate between dynamic and condenser microhones. They have the punch, presence, and flat frequency response curve of a dynamic microphone, without its compression and exaggeration, and they also have a good sensitivity, despite not at the level of condenser microphones. They are faithful to highs and drop them pretty early. Their bass response has no match with the other microphones. Because of this, they are called "dark" and creamy.
Frequency Response Of A Ribbon Microphone
If you like the faithful sound of early microphones, with natural basses and mellow highs, with a low transient response, a ribbon microphone will literally bring life to a recording.
The only shortfall is that ribbon microphones are very delicate. If you hit them, or just play too close to them, the thin aluminium membrane will not withstand the shock and will likely break. Moreover, the ribbon needs periodic retensioning for optimal performance.
Nowadays, many aluminium foil thicknesses are available - the thicker the foil and less detail you will have. Historical ribbon microphones used 6 µm. This is also often used in modern replicas. The tick ribbon makes a voice sound smoother and better, flattening excesses. An unstable and swinging voice will sound very professional with such a microphone, as transients will be slow. 6 µm also confers the ribbon a good resistance against occasional shocks.
Some consider 1.8 µm the Holy Grail, as the microphones acquires the sensitivity of a condenser microphone, still retaining the flat frequency response curve, deep basses and realistic color of a typical ribbon microphone. A voice, or an instrument, becomes very defined and focused, as transients are much quicker. However, this thickness makes the microphones very delicate. Anything below 2 µm will make the ribbon extremely sensitive.
Other typical thicknesses of aluminium foil are 2.5 µm, which is a good compromise between 6 µm and 1.8 µm, and 1.2 µm, which you can easily break just with breathing.
Usually, ribbon microphones do not come with an integrated pre-amplifier. Thus, their output is very low and must be pre-amplified with special gear.
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