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What Kind of Microphone Do I Need?

Microphones play a crucial role in capturing sound and transforming it into electrical signals for amplification or recording. At the heart of most microphone designs is a diaphragm—a thin plate concealed within the microphone's capsule—that vibrates in response to air pressure fluctuations, converting sound waves into electrical signals.


Let's delve into the intricacies of microphone operation and explore the different types available.

 

How do Microphones work?


Microphones are transducers, converting sound waves (fluctuations in air pressure) into electrical signals, which can then be further amplified or recorded. Except for piezoelectric mics, all microphone designs revolve around a diaphragm. This delicate plate vibrates in sync with minute air pressure changes, initiating the transformation process.


The biggest difference between the distinct types of microphones comes down to the nature of the material used for the diaphragm, as well as the polar pattern and how precisely the sound waves are then converted into an electrical signal.

 

What are Polar Patterns?


Before we discuss the types of microphones, we must understand that every microphone has a polar pattern. Polar patterns refer to the directions in which the microphone picks up signal. Some mics pick up signal from all directions, while others only pick up signal from the front or sides. Understanding these various patterns will help you determine which microphone to use for your specific needs.


The Polar Patterns of Microphones


There are 6 types of Polar Patterns:


1.    Cardioid
  • The most common and popular, this heart shaped polar pattern only records what it’s pointing at. Cardioids are typically used for live performances because they will minimize sound coming from other directions such as instruments and sound monitors.

2.    Supercardioid
  • Another popular option for live performances, a supercardioid pattern has a narrower area of recording in the front, but they also pick up a small amount of input from the back of the mic.

3.    Bidirectional (figure of 8)
  • The bidirectional pattern picks up input from two directions and is also known as figure of 8. Mics with this pattern will catch sound from the front and back. Bidirectional patterns are standard in traditional ribbon microphones. These patterns can be used for recording two people at the same time or recording someone who is both singing and playing an instrument.

4.    Hypercardioid
  • Hypercardioid is essentially a hybrid combination of the cardioid and bidirectional patterns. With this polar pattern, sound will be picked up from the front and partially from the back, but the sides will not receive any input.

5.    Lobar (shotgun)
  • The lobar polar pattern is seen in shotgun microphones. Great for precise pinpointing of sound sources. Lobar is similar in construction to hyper-cardioid, but with the addition of an interference tube. This interference tube helps narrow down the focus of the input. This pattern is heavily used for TV and film.

6.    Omnidirectional
  • Microphones with an omnidirectional polar pattern receive input from all directions. These are good for catching the acoustics of a room and tend to produce an open natural sound. Typically used for lavalier mics.

 

Polar patterns can make a huge difference in your result. It’s important to consider the various polar patterns when choosing which microphone will be right for your specific scenario.  


There are also microphones that have multiple polar pattern options that can be changed at the click of a button or the flip of a switch. These mics can be great as an all-in-one recording tool, but they tend to be more expensive due to their versatility.

 

Now that you have a basic understanding of polar patterns, let’s discuss the types of microphones.


The Types of Microphones:

 

1.   Dynamic Microphones

 

  • Dynamic microphones (aka moving-coil microphone) are based on the principle of electromagnetic induction, where the microphone's diaphragm is attached to a small moveable coil of wire and placed inside a magnetic field of a permanent magnet. When a sound hits the diaphragm, it forces it to vibrate inside the magnetic field, effectively causing an alternating current to flow in a circuit following a pattern similar to the incoming sound waves. This creates a clean, clear microphone response without being too sensitive, making it great for a wide variety of tasks.


  • Most dynamic microphones have a cardioid or hypercardioid polar pattern.


Dynamic Microphone Polar Pattern


  • Out of all microphone types, dynamic microphones are typically the most durable, and because they are less sensitive, they're perfect at handling extremely loud signals without distorting. As a side effect, they are also great at rejecting/ignoring unwanted ambient noise. As such, dynamic microphones are a typical choice for live performance, recording localized sound in noisy environments, and for recording particularly loud sound sources.

 

Microphone Input List

2.   Condenser Microphones

 

  • In condenser microphones, the diaphragm is made of a thin metal plate which sits in front of another plate known as the backplate. Together, they form what in the world of electronics is known as a capacitor (in fact "condenser" is an older term for capacitors)—a device that can store small amounts of electrical energy. Sound causes the diaphragm to move, and the change in distance between the two plates effectively changes the electrical signal that passes through the circuit, once again mimicking the pattern of the incoming sound waves.



AKG C414 Xlll Condenser Microphone


A.   Large Diaphragm Condenser Microphones

  • These types of microphones give vocals a full sound and add subtle warmth. Most of these have a cardioid polar pattern, however some can switch between different patterns. As seen above and within the LOTR input list for Tuba, Tipani, etc... The C414 is a highly customizable tool that can be used in a broad range of circumstances. Featuring built-in switches for various levels of bass roll-off, input level padding, and even selectable polar pattern (See polar patterns above), the 414 can be quickly tailored to suit virtually any sound source out there. It features a notably flat frequency response with little tonal coloration, cleanly translating any incoming sound.


Neumann KM 183, Small Diaphragm Condenser Microphone

B.   Small Diaphragm Condenser Microphones

  • These are small thin cardioid mics, sometimes called pencil condensers. As seen above and within the LOTR input list for flute, oboes, clarinet, etc... Very compact, and they are great at picking up sounds exactly as they are, without any added coloration, as well as bringing out the subtleties. Because of these qualities, these kinds of microphones are often chosen as drum overheads, as well as for recording acoustic instruments, and entire orchestras.


Royer R-121 Ribbon Microphone

3.   Ribbon Microphones

 

  • Ribbon microphones are similar in their operational principle to the dynamic microphones, as both rely on electromagnetic induction, however here instead of the induction coil, a thin piece of metal ribbon is suspended in the magnetic field. Ribbon microphones are often characterized as possessing a pleasantly warm and smooth response, and for this reason, they are well-loved by many recording engineers, and artists. Ribbon mics are, for instance, quite commonly used on brass instruments—both as a recording mic for soloists or for groups of instrumentalists acting as a section. With some care, they can provide a similar warmth for guitar cabs (just watch your volume!), and they are often used to add a nostalgic character to vocals or other solo instruments. A pair of ribbon mics can even be used in a novel stereo configuration for drums or ensemble recording.

 

Understanding the workings and nuances of dynamic, condenser, and ribbon microphones will empower you to choose the right tool for diverse audio recording needs. Each type offers unique characteristics that cater to specific preferences and applications in the vast world of sound capture and reproduction.

 


Sources:

NMR EVENTS BLOG

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