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Explore the design differences between the four most common types of microphones available
Determine which family of mics are the best for specific uses
Find out what ‘polar patterns’ are, and why they matter
Whenever you find yourself in any live or recording environment, it’s safe to say that deciding which of the microphone types is used is one of the biggest factors in how well that performance is going to be captured.
Just as with most things related to recording or live sound reproduction, picking the right one can be a ‘make or break’ proposition. But with all of the choices out there, how do you know which of the different types of microphones is the right one for the purpose?
In order to clear up the confusion, we’re going to take a look at the four main types of microphones you’ll come across; on top of that, we’ll also get into some of the finer details about mics such as polar patterns (no, we aren’t talking about winter weather) and also discuss how diaphragm sizes can have an impact.
How Do Microphones Work?
Before we get into the down and dirty details, a quick review of how a microphone works is in order…
In broad terms, all types of microphones work in a similar way. Sound waves are produced from either an instrument or from someone’s vocal performance. The microphone itself then captures these waves and converts them into an electric signal. This signal is then fed into either a recording device or a PA.
Seems simple enough, right? Well, it is…but as with most things, there are finer points that need to be understood so that you pick the right type of microphone to begin with.
Will selecting the wrong one absolutely ruin a track or a performance? ‘Ruin’ may be a strong word here, but there’s no doubt that having the right tool for the job will give you the best results.
Types Of Microphones
Overall there are four main microphone types that you’ll find available to use: condenser mics, dynamic mics, ribbon mics, and shotgun mics. While some of the technology behind each type may be similar to another, the differences are typically great enough where a particular kind would be preferred over another given the intended use.
So, without further ado, let’s break them down one by one while also looking at the pros and cons of each type.
With a dynamic microphone you’ll find the most simple design among all of the main mic types. Incoming sound waves strike what is called a ‘diaphragm’, which is a thin piece of material that is designed to easily vibrate when exposed to sound wave pressure.
Behind the diaphragm in a dynamic mic is a magnet and coil setup which generates a magnetic field. As the diaphragm vibrates within that field, the energy is translated to an electric (audio) signal which is then output from the mic itself.
Pros of dynamic mics
The simple design of dynamic mics tends to make them fairly cost-effective to manufacture, therefore they will typically be among the cheaper mics you’ll come across.
If you’ve ever stood in front of a loud sound source (such as a kick drum), you’ll get that feeling of actual air moving; that’s referred to as ‘sound pressure’. The louder the sound, the higher the sound pressure level (SPL) is. Dynamic mics are rugged and a great choice for environments where high sound pressure levels are to be found.
This is a prime example why an industry-standard dynamic mic like the Shure SM57 is many a soundman’s go-to choice for live performances where, for example, cranked electric guitar amplifiers may be all over the stage.
Dynamic mics are also ‘plug and play’, meaning there is no need for any external power source (called ‘phantom power…more on that later).
…and the cons
While dynamic mics are a good choice for live use, they may not be able to capture softer sounds or higher frequencies as well as other mic types. This may make them not the best option for use in a studio setting where more delicate sounds are being transferred to tape (yeah, we know that everyone is going digital these days, but you get the point…)
Condenser microphones also use a diaphragm, but the overall construction is a bit different.
With a condenser, the magnet and coil setup is replaced with a back plate, and the diaphragm itself has a power source fed to it. This is called ‘phantom power’, and you’ll usually find a button on your interface, preamp or console which feeds the power through the mic cable itself.
(A word of caution here: make sure to turn on phantom power before you start to gain stage or turn your faders up to avoid any nasty pops which could damage your monitors…that’s a bad thing!)
As the distance between the diaphragm and the back plate is altered (by the vibrations resulting from sound waves), a voltage change is then translated into the main audio signal.
Small Diaphragm Condenser vs. Large Diaphragm Condenser Microphones
Generally related to condenser mics, you’ll see various models described as having a ‘small’ or ‘large’ diaphragm.
A large-diaphragm condenser mic will generally have a deeper response to low frequencies (due to the size of the diaphragm being bigger) but will also be more sensitive. It also tends to give out a bigger output than a small diaphragm. This means its signal-to-noise ratio is a lot bigger, making it a great selection for recording quieter instruments.
On the other hand, a small diaphragm condenser mic will be more suited to higher frequency instruments such as cymbals. A small diaphragm will also have a smoother frequency response.
Condenser microphone benefits
Condenser mics (such as the Neumann TLM102 or 103) are typically used for recording sounds with finer details. This is why they are often used for recording vocals along with more precise sound capture needs (such as softly fingerpicked acoustic guitar passages or other acoustic instruments).
Additionally, the frequency response with these types of microphones tends to be better in the higher frequency ranges.
Downsides of condenser mics
Condenser mics are, however, quite fragile and need to be put away after each session. Believe it or not, any dust that finds its way onto the diaphragm can cause problems with the mic further down the line.
That being said, not only do they need to be stored properly but care should be taken if any extreme sound pressure levels are going to be involved to avoid damage to the diaphragm.
And…this is typically a big one…they can be expensive, often costing several times that of a standard dynamic mic.
Ribbon mics are actually a type of dynamic microphone; however, they are a lot more fragile due to the way they are constructed. They are called ‘ribbon mics’ due to the shape of the diaphragm itself (typically long and thin). With a ribbon mic there is no coil, as the ribbon itself is suspended between magnetic poles.
Upsides of a ribbon mic
The way ribbon mics sound can be loosely compared to a condenser mic, however, they do have quite different characteristics. Unlike a condenser, a ribbon mic tends to sound smoother and darker. They are a great choice for getting a ‘warmer’ sound that most engineers find to be more realistic.
Their design and construction also eliminate the need for any phantom power requirements.
Reasons against using ribbon mics
Ribbon mics are notorious for being extremely delicate. High SPL’s, not taking gentle and proper care with storage and use, and accidentally switching on phantom power in error can easily damage them.
Cost is a big factor when it comes to using a ribbon mic – yes, they can outperform some of the other mic types, but be prepared to pay for the privilege!
Certain models of ribbon microphones may have a relatively weak signal, which may require additional preamps to boost the output to usable levels.
Shotgun microphones (also called ‘line microphones’), aside from having a really cool name, are great at picking up a pinpointed source of sound. This is due to having an extremely narrow and directional field where sound is captured.
It’s important to note that a shotgun mic can have either a dynamic or a condenser design. From that perspective, they are considered one of the microphone ‘types’ only due to the extremity of their function and purpose.
If you’ve ever witnessed a behind-the-scenes clip of a TV or film shoot, you’ll probably have seen a shotgun mic (typically a long cylinder with a small diameter) being pointed at the actors above the camera.
Pros and cons of using shotgun mics
Shotgun mics are highly accurate, making them a great choice for situations such as this where you would want to reject any off-axis sound. That being said, they wouldn’t be a great choice in a studio where you wanted to pick up the natural sound of the room.
As they can have either a dynamic or a condenser-type design, the individual pros and cons of each of those technologies needs to be considered as well.
When choosing a suitable microphone, a producer will consider what is called its ‘polar pattern’. Polar patterns (sometimes referred to as ‘pickup patterns’) are how a particular microphone will respond to sound waves coming to it from different directions, with a big factor in that being related to specific frequencies.
Essentially, using a microphone with a specific polar pattern will change the directional impact a microphone has on capturing sound. There are several options to choose from, each with their own best applications and practices.
Many microphones will allow you to switch between polar patterns, however, a cardioid is often the ‘default’. A cardioid polar pattern means the microphone will pick up sound in a heart shape (hence the name) projecting forward while also rejecting most frequencies from the base.
A hypercardioid polar pattern operates in a similar way to that of a cardioid configuration. These types of microphones offer a greater amount of rejection from the sides, however, they will pick up more sound from the rear of the mic.
Omnidirectional microphones, often just referred to as ‘omni’, record sound evenly from all directions around the mic. These are a great option if you want to capture the sound of your room.
However, using a mic with this type of polar pattern does have drawbacks. A good example of this is if you are recording vocals and an acoustic guitar at the same time. In this case, you can actually end up with a significant amount of acoustic guitar spill into the mic.
A figure 8 (sometimes called a bidirectional) picks up sound in an ‘8’ shape around the mic. If you imagine two microphones pointing away from each other then it’s easy to picture how a figure 8 pattern will function. Because it rejects sound from the sides, a figure 8 microphone is a great option for recording two vocalists at once.
Other Microphone Features
Aside from polar patterns, you may find a couple of other options on your microphone that can help to further refine and define the output.
High Pass Filters (HPF)
Some people do get confused by the name and functionality of filters such as an HPF but it’s relatively simple: they allow highs to pass through, so an HPF can also be viewed as a bass frequency cut. As a reference point, a typical threshold for HPF usually lies around 50-80Hz but can often be 100HZ or above.
You will probably find you won’t hear a huge difference to your vocals or instrument with the HPF on or off, however, it will eliminate any unwanted hum or rumblings that may be being picked up in the room that would cause a muddier sound.
A pad will simply reduce the output level of the microphone by a certain amount of dB. If you are recording a drum kit, you will commonly find you need to use this switch due to the extremely loud volume of the instrument.
When gain staging (which is the process of adjusting levels at each amplification point in a signal path, therefore minimizing distortion and optimizing the overall signal-to-noise ratio), you’ll know whether to switch the pad by your signal level.
If the signal is extremely hot with only a slight increase in gain, it’s best to reduce this at the source via the mic pad (although you will often find a pad option on your console or interface).
Wrapping It All Up…
So what does all of this add up to? Which of these types of microphones is the best choice for your specific needs?
The answer is essentially this: the right mic is the one that’s right for the job.
While that may sound like an extremely vague and general statement, it’s also very accurate. Which of the types of mics is the ‘right’ one for the purpose at hand will depend on a fair amount of factors that you, as a recording engineer (whether in a home studio or a professional one) or a soundman, will have to consider.
Having the knowledge of the different microphone types, what makes them tick inside (how they work), and what applications they are best suited for will allow you to make the best selection for a particular purpose.
Also, knowing the inherent differences with the various types of polar patterns can also be a big help with getting the results that you are looking for.
All of this means that your recordings and/or live sounds will be the best they can possibly be…which is really the whole point of it all!