Everyone wants to know what the best microphone is for any given job. If you’ve ever taken the time to dig around on a recording forum, you’d know that the capabilities of a mic are often subjective. If you're struggling with choosing a microphone, you've finally come to the right place. This article aims to clear up the confusion surrounding microphone types, polar patterns, recording techniques and accessories, helping you make the best choice when buying or using microphones.
Microphones can be categorized by the inner workings of different mechanisms designed to interpret acoustical energy as an electrical signal. These different mechanisms, known as capsules, give microphones distinct characteristics that can either help or hinder a recording depending on the source, the room, or the capture technique. Let's look at some common microphone types that will useful to you in the recording studio.
Condenser microphones are among the most common types of microphones that you will find in the studio. They interpret acoustical information when a frequency vibration reaches two plates within the capsule, changing the distance between them. Electricity is needed to get these plates to function as designed. Condenser microphones are either powered by their own source, or through an external source of phantom power.
Condenser microphones are known to have a flatter frequency response than its dynamic counterpart. They are also characterized by their sensitivity, which allows them to interpret quiet and distant signals with accuracy and detail. This sensitivity can be a bit of a hindrance when trying to record a source that has high SPL's, but in most instances, engaging a pad on the microphone or on the preamp can fix this problem. Condenser microphones are a top choice for most vocal recordings, as well as on instruments that contain a lot of detailed high frequency information.
Due to their design, condenser microphones are somewhat fragile in comparison to the dynamic microphone. Great care and attention should go into placement of these microphones to ensure something like an awry drum hit doesn’t smash them up. The humidity of a microphones storage and usage environment should be properly maintained as places with higher humidity levels can affect the functioning of some capsules. A relative humidity of anywhere between 45-55% would ensure safe usage and storage. For particularly wet environments, a dehumidifier may be an important addition to your studio. Silica packages can also be used where microphones are stored to keep them dry and ready for the next use.
The science behind condenser microphones may not seem to be of use to you in capturing great recordings, and some ways you’re right. Knowing how a microphone works won’t win you any awards. It will however allow you to associate the unique sounds of a condenser with its capturing method, helping you differentiate its sound between other types of microphones. The knowledge of a condensers design will also help you care for and maintain its functionality for years to come. Next, let’s look at some variations of the condenser microphone.
Large, Medium, and Small Diaphragm Condensers
Condenser microphones can have different sized capsules, with the large variation being well suited for just about any job needed. The smaller variation is a preferred choice when ultra-responsiveness and directional precision are desired.
Shotgun microphones are an extremely directional condenser microphone used to capture a source from a distance, while picking up very little noise from the environment around the source. They are most commonly used in speech and film.
Boundary microphones are small-sized omnidirectional condensers that are designed to be placed near or flush with a surface. This gives them advantages in picking up a flat, accurate frequency response as there is less phase interference between the direct source sound and reflected room sound.
Measurement microphones have an extremely accurate and extended frequency response. They are sensitive omnidirectional microphones that are useful for measuring acoustics, testing and fine tuning speakers, or anywhere else that an accurate representation of sound needs to be measured.
By now you should have a foundational understanding of condenser microphones to help carry you through your recording endeavors. Let’s now look at another type of microphone that is equally of use to you as a recordist.
Dynamic microphones are a complementary counterpart to the condenser microphone. They interpret a sound waves through the use of a wire coil and magnet. The wire coil runs through the magnet, and is attached to the diaphragm of the microphone. When this diaphragm vibrates, the coil moves backwards and forwards through the magnetic field, transducing the acoustic energy into electric energy. Unlike condenser microphones, dynamics do not require phantom power to operate.
Dynamic microphones have a limited frequency range, often tailored to accentuate certain areas on the spectrum. For instance, a specific dynamic mic could have an extended low end frequency response and a scooped sounding midrange. These characteristics would bode well for miking the bass drum of a drum kit. Dynamic microphones are also much less sensitive to high SPL's so they are often a go-to choice on loud sources such as guitar and bass amps, individual close microphones on a drum kit, or even certain vocalists.
As far as durability goes, not many microphones can withstand the abuse that your even your average dynamic microphone can handle. There is a common belief that having phantom power switched on when a dynamic microphone is plugged in can damage it, but in most cases this is not true. Dynamics are considered to be a reliable workhorse for the recordist, which is an absolute joy in a profession where maintenance and upkeep are both important and expensive.
Technically, dynamic microphones perform the reverse function of a speaker. In fact, if you were to plug in a dynamic microphone as an output source, it would produce sound. If you experiment with this, keep the audio low so you don’t cause damage to your microphone. This concept has been utilized in sub-bass capturing devices made out of speaker diaphragms.
Ribbon microphones which used to be an expensive and extremely delicate microphone to own and care for, have made a resurgence in the recording studio in recent years thanks to lower prices and improved durability. Ribbon microphones capture sound through changes in the speed of air molecules that move a thin aluminum strip, suspended between the poles of a magnet. Much like dynamics, phantom power is not needed to operate a ribbon microphone.
Ribbons are known for their vintage sound which may be a useful addition to your palette of capture options. They are exceptionally good at taming harsh sources and are also known for having a good transient response, making them a worthy capture tool in the studio. All ribbon microphones are of a bidirectional polar pattern which makes them even more specialized in what they can and cannot do for you as a recordist. We will explore polar patterns a little more in the next section.
When caring for a ribbon microphone, many precautions need to be taken. The aluminum ribbon is quite delicate, and can be damaged by the movement of excessive amounts of air. A good test is to put your hand where you intend to place a ribbon microphone to feel if there is any air coming from the capture source. If you feel air, you should use a pop filter to prevent damage to the ribbon. You should avoid dropping a ribbon microphone at all costs, as much like condensers, they can easily be damaged from rough handling. Phantom power is often viewed as being a ribbon killer. While some ribbon microphone companies say that their microphones are impervious to the typical dangers phantom power, it’s best to just keep the 48v switched off whenever using them.
Piezoelectricity uses crystals to transduce a source into an electrical signal. These crystals produce voltage in response to pressure which causes them to vibrate. This technology is utilized in contact microphones, commonly used to amplify acoustic instruments such as guitars, violins, cellos, and more. Contact microphones are made to detect surface vibrations rather than airborne ones, allowing for a sound that is virtually free from airborne feedback. While the sound of a condenser, dynamic, or ribbon microphone is seen as more desirable, the use of contact microphones for live application is often more practical. Contact microphones can also be used to trigger drum hits for sample replacements.
There is a lot more variation to microphones than just their method of transduction, as they become even more specialized by their polar pattern. The use of different microphone types in combination with different polar patterns will allow the recordist to experiment with many commonly used recording techniques. A polar pattern refers to how well a microphone can listen to sound from different directions. There are omnidirectional microphones which can listen to sound equally from all directions, unidirectional microphones which predominantly listen to one direction, and bidirectional microphones which listen from both the front and the rear equally. Some microphones even have the ability to switch polar patterns, making them extremely handy and diverse for a recordist. A microphone's polar pattern is typically expressed on a diagram included with the microphone. Let's look a little closer at each of these polar pattern categories.
An omnidirectional microphone has the advantage of picking up sound from all directions. This means it does not need to be aimed in any particular direction in order to perform as intended. As you can imagine, this would have many benefits in the studio, for instance, when trying to capture the performance of an acoustic guitarist who keeps moving around. In this situation, what would be a nightmare to record for a unidirectional microphone, is mitigated by the use of an omnidirectional microphone. While this ability to listen to everything in some situations may feel like a blessing, not being able to aim its listening away from undesirable room sounds can be a curse as well.
A bidirectional microphone, also known as a figure of eight microphone, can pick up sound from both the front and the back of the microphone, while almost completely ignoring the sides. The ability ignore side information makes these microphones valuable for achieving isolation in a live tracking environment. They are also essential for a few recording techniques which we will explore after polar patterns.
Unidirectional microphones are sensitive to sounds from one predominant direction. This makes microphone placement particularly important as a unidirectional microphone will mostly pick up whatever you point it at. The most common unidirectional microphone is a cardioid microphone.
The cardioid polar pattern in microphones was created by combining both an omnidirectional polar pattern and a bidirectional polar pattern. Sound arriving at the front of the microphone is picked up by both the omnidirectional and the bidirectional pattern and sound arriving at the sides of the microphone is picked up only by the omnidirectional pattern. This means that the front of the microphone will pick up twice as much sound as the sides of the microphone, as the sides are only being picked up by one of the polar patterns. At the back, the positive signal of the omnidirectional pattern combined with the negative signal of the bidirectional pattern cancel each other out. This effectively mutes the rear of a cardioid microphone, resulting in a microphone that listens to what you point it at and ignores the opposite direction. As you can imagine this has many useful applications for sound recording.
Eventually, different amounts of omnidirectional and bidirectional signals were blended and a new breed of polar patterns emerged. The subcardioid pattern is the product of having more omnidirectional signal influence than bidirectional. This creates a polar pattern similar to the basic cardioid, but with less rejection of sound in the rear and a heightened sensitivity in the sides. Supercardioid and the even more directional hypercardioid polar patterns have a stronger bidirectional influence in relation to the amount of omnidirectional pattern that is mixed in. This increases their sensitivity in the front compared to the sides, and also produces a bulbous shape at the rear of the microphone, due to the overpowering influence of the bidirectional signal.
These polar patterns in combination with different microphone types gives the recordist a number of options when deciding how to capture a source. Experimenting with different microphone types and different polar patterns will help you develop an ear for how you want to capture a source. While the art of experimentation is certainly a valuable trait of a recordist, knowing some tried and true recording techniques can really be a catalyst towards quality recordings.
Recording techniques can help a recordist to discover their personal preferences when trying to achieve a sonic goal. By starting off with well known techniques you will begin to develop these preferences, eventually tweaking them to suit your source and room for even better results. Below are some good starting points for both mono and stereo recordings.
Recording with a single microphone is a fairly simple process. You will need to assess your capturing objectives before placing any microphones. Below are some mono recording techniques to help you achieve different capture results.
Close miking is a recording technique in which a microphone is placed relatively close to a source to reduce the influence that a room has on the audio capture. This technique is often described as being dry or dead sounding, as the source volume greatly outweighs the volume of room reverberations. The philosophy is that reverb or delay can be tastefully added and adjusted separately from the dry signal, allowing for more control in achieving a desired sound. This technique is particularly useful when a less than desirable recording environment limits your options. It is also useful when recording multiple sources to minimize bleed between the microphones. Frequency response can be affected by close miking, especially in directional microphones like cardioids. Close miking with a cardioid microphone results in a frequency boost in the low-mid range? which can be used strategically to thicken up a source. Often this close proximity effect adds unwanted muddiness to your audio, so be aware. The proximity effect is unlikely to ruin your audio beyond repair, as it can be reigned in with EQ via post processing or in the signal chain before even reaching your DAW.
Distant miking is essentially the inverse of all the advantages and disadvantages that come with close miking. The resulting audio picked up by a distant microphone tends to be more natural and ambient. This is particularly desirable when the room that the source is being recorded in fits the recordist so sonic goals. The proximity effect is not a factor for distant miking either, which should mean less problem solving with EQ. Instrument bleed may however limit you with distant miking if you plan to record multiple sources at once.
Room miking is much like distant miking in that the ambience of the room is part of the desired sound to be captured. The main difference in room miking is that the volume of the ambience should be louder than the volume of the actual source. This balance gets easier to achieve the larger the room gets. Instrument bleed into a room microphone may cause problems when simultaneously recording different sources, especially when the room sound is intended for a specific source.
Overdubbing is the process of recording one or a group of instruments onto an existing recording. A musician can monitor and play to any existing tracks in the session. These existing tracks should be balanced in a way that the musician can perform with accuracy and emotion. The microphone type and polar pattern of a new source recording should compliment any existing tracks that you have recorded in the session, making the newly recorded source fit into the mix with ease. Eventually, all of these layers of overdubs will add up to a complete arrangement. Today, it is common for a studio recording to be created through overdubbing as less sources need to amalgamate into the perfect performance. With that being said, what’s gained in tweak-ability may be lost in terms of groove as recording using overdubs may never create the unique vibe of a group of musicians performing simultaneously in the same room.
Recording with more than one microphone exponentially complicates the recording process with every added microphone. This is partially due to a phenomenon known as phase cancellation. Phase cancellation is when the same sound arrives at two or more microphones at slightly different times, causing a sound of incoherency when blended together. When you have been a recordist for some length of time, the sound of an out of phase microphone or microphones will be easily diagnosed. This sensory feedback will develop the more you hear the negative effects that phase cancellation has on your recordings. Phase cancellation is often described as a thin or weak sound. The best way to check if any two microphones are in phase with each other is to listen to them in mono. Two wide panned microphones of one source may be completely out of phase, but it may be less obvious for you to hear when they are coming from two different locations in the stereo field. By checking these two microphones in mono, it should be apparent to you whether or not they are in phase, or if they need to be adjusted. In extreme cases, phase can be adjusted by reversing the polarity of one of the microphones. More often than not, this solution can fix the phase problems you are having. Sometimes phase cancellation will be less drastic but will still causing audible issues. In this circumstance the recorded stem files can be manually lined up in your DAW, matching the signal peaks and valleys of both files as close as possible.
Being aware of phase cancellation, it might seem obvious that throwing microphones on stands and hitting the record button is likely going to result in more work for you further into the process. Knowing some basic stereo recording techniques can help you get the stereo recording you desire, without as much of the guesswork.
The X-Y microphone configuration is a phase coherent stereo recording technique. It is created using two small or large diaphragm cardioid microphones placed with their heads together at a 90 degree angle. The left microphone captures the right side of a source, while the right captures the left. Because the microphone diaphragms are so close together, the source sound arrives at the same time, providing phase coherency. It is important to get the heads of the two microphones close together without touching each other. Any contact between the microphones may be audible in the resulting audio capture.
Named after its inventor, Alan Blumlein, the Blumlein Pair is a stereo recording technique that is nearly identical to the X-Y configuration. The difference between the two is that rather than using two cardioid microphones like in the X-Y configuration the Blumlein Pair requires two bidirectional microphones. It is known for capturing a very realistic performance of a source within the environment that it is being recorded in.
This stereo recording technique was first implemented by Office de Radiodiffusion Télévision Française, a French broadcast commission often referred to as simply ORTF. Due to its origins, the ORTF configuration has been appropriately named and has become widely adopted by recordists around the world. To create the ORTF configuration, two cardioid microphones need to be placed with their heads 7” (17cm) apart and at an angle of 110 degrees. This spacing is similar to the distance of human ears, so placement of the ORTF configuration can be as simple as walking around a room to see where a source sounds best and placing the microphones there. The ORTF configuration tends to be less phase coherent than the X-Y technique, but it holds up well enough with an enhanced perception of width.
The NOS recording technique was first used by Dutch broadcast service, Nederlandse Omroep Stichting. Much like the ORTF configuration, the techniques name is also an acronym derived from its origins. It also happens to be very similar in nature to the ORTF technique. To create the NOS configuration, two cardioid microphones are placed with their heads 12” (30cm) apart and at an angle of 90 degrees. The placement, benefits, and drawbacks of this technique mirror that of the ORTF with a slightly tweaked stereo image because of the angle and spacing differences.
The A-B stereo recording technique is common, but also provides some challenges as far as phase relationships go. To create this technique you can place two cardioid, omni, or bidirectional microphones apart from each other and directed at different areas of the same source. This technique can be used to provide exaggerated width or even at times to capture tonality differences of the same source. To maintain a relatively phase coherent recording, a 3:1 ratio rule can be implemented when placing the microphones. This rule suggests that for every 1 standardized unit of measure the microphones are from the source, 3 units of the same measurement should distance the microphones from each other.
The M-S, or Mid-Side, recording technique is created with the use of a cardioid microphone and a bidirectional microphone. The cardioid microphone is directed towards the sound source at a location that gives a pleasing tone. The bidirectional microphone is then placed perpendicular to the cardioid microphone, picking up both the left and the right side of the room in relation to the source and cardioid placement. The bidirectional microphone capture is then copied in the DAW to a second track, and the polarity of the copy is flipped. These two bidirectional microphones are then hard panned left and right and blended in with the capture of the cardioid microphone. The more influence the bidirectional signal has in relation to the cardioid signal, the more depth the source is perceived to have.
The Decca Tree configuration was created as a variation of the A-B recording technique, with the addition of a center microphone. This microphone configuration is most commonly used when capturing orchestral performances. The configuration requires a dedicated T-shaped microphone mount, placing one microphone at the end of the stem facing center, and two other microphones on the left and right ends of the crossbar pointing left and right respectively. This microphone array is traditionally used with omnidirectional microphones, but can just as easily be created with cardioid microphones.
These techniques should give you a good starting point for recording both mono, stereo, or any other multiple miked source capture. Feel free to experiment with these concepts when deciding how to best capture the next source you are required to record. Let’s now look at some microphone accessories you may want to consider to help make your job as a recordist a little easier.
There are several products available that can take away some of the stress and pressure that often comes with recording. While some of these accessories may not exactly qualify as minimalist purchases, all of them are relatively inexpensive and can make a huge difference to the quality of your recordings.
As mentioned in the accessories area of the last chapter, the quality and variety of microphone stands will be an invaluable investment. Quality stands will ensure that your microphones are safely secured, and will not sag or topple after finding an ideal capture location. A variety of stands will allow you to capture sources from just about any height or angle. Some popular mic stand choices are straight stands, boom stands, and low level stands.
A Shock mount screws on to a mic stand and acts as a cradle for your microphone. Often when capturing a source, unwanted noise is picked up by a mic directly attached to a mic stand. This noise could be foot tapping, floor shuffling, microphone stand bumping, or many other unwanted noises. A shock mount cradle suspends your mic from the stand, providing some isolation from noise transferring from the mic stand into the microphone.
A microphone activator sends a large amount of clean gain to your microphone in order to capture sources at a more respectable recording level. Some dynamic microphones can benefit from this when recording certain sources. You can think of it an activator as performing the opposite function of a pad, helping you recording quiet sources without sacrificing quality.
Pop filters are designed to reduce the popping sound created by a blast of air hitting the microphone. This popping is most noticeable when singing plosive sounds such as words starting with hard t’s, k’s, p’s, d’s, g’s, and b’s. Sibilance, the ess-like sounds created by a vocal, is unaffected by a pop filter. Pop filters are often made from single or multiple layers of a nylon-like material, stretched over a circular frame. This frame is attached to a gooseneck, which typically clamps onto a microphone stand. Homemade pop filters can be made with nylon and a coat hanger, if you are in a situation where you need to improvise.
A wind screen is a foam cover that protects a microphone from wind or plosive sounds. Many microphones have an internal windscreen that is built around the diaphragm. External windscreens, which simply slip over the microphones head basket, are also common. These are typically used in outdoor recording environments for their added protection against wind noise. These windscreens do come at a disadvantage in studio application as the protective foam also attenuates the microphones high frequency response. The denser the foam, the more severe the high frequency attenuation will be. For this reason, pop filters are the preferred choice for controlling plosives in the studio.
A reflection filter can provide extra absorption around the rear and sides of a microphone when capturing a source where a particularly dry sound is desired. They are predominantly used when recording vocals to reduce unwanted room reflections from making it into the recording.
Acoustic isolation platforms exist for different gear including guitar and bass amps, as well as microphone stands. These isolation platforms decouple a source or stand from the ground, which can reduce the amount of unwanted noise that a microphone captures.
You should now be well equipped when buying and using microphones and microphone related accessories. Be confident when going into your microphone locker or local music store that the knowledge you have is enough to point you in the right direction, no matter what the recording task at hand may be.