Reaping in the Dark – Part 2.3: An Intro to Microphones

Microphone on stand.

Welcome back to Reaping in the Dark. Today, we’ll be taking a crash course on microphones. Read on to learn exactly what they are, what they do, and how they do it, as well as get into some history on famous models of each type.

 

What’s in a Microphone?

 

As mentioned in the previous article, a microphone is a tool that converts the changes in pressure we perceive as sound into an electrical signal, which can then  be manipulated and recorded to produce the audio we work with. Microphones are used to capture everything from a delicate violin melody to ear-splitting heavy metal guitar rigs. Furthermore, microphones can be used in several configurations, from a single mic on a solo singer, to a pair of microphones placed perfectly to capture the size and depth of a full orchestra, to a multi-mic setup to capture and isolate different elements of a single drum set. With so many uses, we get quite a few types of microphones, and it’s important to know what to use and when to use it. When working with microphones, we can easily pick the right tool for the job by considering two elements: how the microphone captures sound and the microphone’s polar pattern.

 

The volume of what we’re recording dictates how best to capture the sound; use a delicate microphone on a source that’s too loud and you could literally destroy the microphone, or pick one that isn’t sensitive enough and you won’t capture all the nuances of an expressive instrument. Our recording environment and how we wish to use the audio we capture dictates the polar pattern, which is the term that describes the pattern in which the microphone “hears” what we are recording. Some microphones allow for a narrower scope, allowing for precise and isolated recordings of something like the different pieces of a drum kit. Others, on the other hand, have a wider range, allowing for the capturing of the sound of a room as much as the instrument they are pointed at. Let’s start by looking at some of the ways microphones pick up sound.

 

Dynamic Mics

 

The most common microphones you will probably come across are dynamic mics. These are relatively cheap and very sturdy; the workhorse of the microphone world. They capture sound by using a diaphragm attached to a coil. Sound that the microphone is exposed to causes the diaphragm attached to the coil to move back and forth, and a magnet inside the microphone allows the movement of the coil to produce the electrical signal which is output by the microphone.

 

The sturdiness of these microphones have made them a staple of the live sound world, where they are rugged enough to withstand the demands of tours and abuse from live performances. Furthermore, they are preferred for their ability to be much more focused than other types of mics, making them handy on crowded stages, which has also made them the favorite of bedroom producers. With their relatively decreased sensitivity, they are very forgiving compared to others if you are working in less than ideal circumstances. Finally, their build makes them well suited for louder applications, such as recording a high volume guitar amplifier or drums.

 

Arguably some of the most famous microphones in this category are the Shure SM57 and SM58, a nearly identical pair of microphones that only differ in their capsules, the part of the microphone that contains the elements used to capture sound. Both contain essentially the same “insides”, however the SM57 has a capsule with a shape more suited for instrument applications, while the SM58 has one more suited for vocal applications. These microphones are legendary, and there are stories of them being able to withstand abuse of mythical proportions. As a professor of mine once said, “If you ever had to go down a dark alley with nothing to protect yourself but a microphone, you’d want an SM57.” I myself once (accidentally) dropped my SM57 on my kitchen’s wood floor, and there is now a dent that shows that in the fight between SM57 versus floor, the SM57 won. (Never mind the reason I needed to have a mic set up in my kitchen.) Both of these are relatively cheap, with each coming in at around $100, making them a great first mic, while still having countless professional studios and stages across the world to vouch that even professionals can find a purpose for one or more of these wonders of musical engineering.

 

Condenser Mics

 

If you are recording a loud source or need something that’s tough, you reach for a dynamic mic. If you want to bring out the subtle nuances of quieter sources such as the human voice or an acoustic guitar, you reach for a condenser. These microphones, like dynamic mics, use a diaphragm to sense sound. However, unlike dynamic mics, the diaphragms on condenser mics are one of two plates of a capacitor inside the microphone instead of being mounted on a coil. The plate that serves as a diaphragm is made of extremely thin and sensitive material, and like the dynamic mic the back and forth movement of this plate relative to the second plate creates the electrical signal the microphone then outputs. Because of this build, it takes a lot less to get the diaphragm of a condenser mic moving than it does the coil-mounted diaphragm on a dynamic, making them more sensitive.

 

Condenser mics are typically more expensive than dynamic mics, so the price of entry is a little higher. With this greater investment though, comes a tool that is typically much more sensitive than most dynamic mics. As mentioned above, these mics are favored for their ability to pick up on the subtle nuances of expressive instruments, and they can be used in a wide variety of configurations to create a richer sound. When recording a guitar amplifier in a nice sounding room, you can stick a dynamic mic close to the speakers to get the direct punch of the amplifier, and set a condenser pulled back a bit to get the sound of the amplifier in the room, then blend the two to get a fuller sound than you would with just one mic. Throw a pair of condensers in a stereo configuration on an acoustic piano or guitar and you have a really rich stereo representation of the instrument.

 

Finally, no discussion of condenser mics is complete without touching on the need for phantom power. Most condenser mics require an external power source to work, and this power is typically provided in the form of 48 volt phantom power that can be carried to the mic on the same cable which the signal is output from. Early models of condensers used a dedicated external power supply, however technology was eventually developed which allowed for the necessary power to be delivered via the same cable which carried the output signal of the mic, leading to the nickname of “phantom” power because of the lack of any additional cables to carry the power being supplied. It is extremely important to know whether or not your mic requires phantom power. Most modern devices which allow connection to a mic can provide phantom power via at least one of their mic inputs, so there is rarely a need for a dedicated power supply anymore. However, it is extremely important to know whether or not your mic requires phantom power. If you don’t supply it to a mic that needs it, the mic won’t work. But supply it to a mic that doesn’t need it and you could potentially damage the mic. Finally, it’s best practice to not turn on phantom power until after the mic that needs it has been plugged in, and turning it off before the mic is unplugged.

 

One of the most famous models in this category is the Neumann U87, used often for recording speech and vocals. Coming in at $3,200 new and between $3,000 and up for a used vintage unit, it is certainly not a cheap mic. Advancements in technology have allowed for the production of less expensive condensers making them increasingly more affordable, including several lower priced clones of the famous U87.

 

Ribbon Mics

 

The third and final type of mic that you will most likely come across is the ribbon mic. These are some of the most expensive and the most delicate mics available. Like those previously discussed, their operation is based on the vibration of a diaphragm. However, unlike those mics, ribbon mics use an extremely delicate ribbon of material that is suspended in a magnetic field to detect the changes in pressure that the source they are recording produces. These ribbons are thinner than a human hair, and are typically very fragile. Drop one of these or in any way expose the ribbon to sudden changes in pressure beyond its limits, and you can easily damage that delicate thin strip of material. Even something as relatively harmless as a strong gust of wind or harsh vocal plosive can damage a ribbon mic.

 

Ribbon mics are prized for their warm and mellow sound. I personally love the sound of ribbon mics on female vocals, and the one ribbon mic I own works wonders on my upright piano which is located in a room with hardwood floors and bare walls that tend to create a more prominent high end to the already bright sound of the piano. Due to their typical polar patterns, ribbons are also highly preferred for midside stereo recording, a mic configuration that pairs two mics with complementary polar patterns to create a stereo image that can be controlled without physically moving the mics. Thanks to advancements in technology, it is much easier to produce these mics now, so getting your hands on one of these gems is now more affordable than ever.

 

One of the most famous models in this category is the Royer R-121. Coming in at around $1,300 new, this is not a cheap microphone, but there’s a reason this microphone has become synonymous with ribbon mics. Ironically, one of the most famous mic pairs has become the Shure SM57 and Royer R-121 for recording guitar amps; a perfect example of how something so cheap can bring out the best in something so expensive and vice versa.

 

Polar Patterns

 

A microphone’s polar pattern can be described by its “shape.” When expressed by a visual representation of the way in which a microphone detects sound, the shape this produces gives us an idea of which directions the microphone will pick up sound and where it will reject it.

 

Omnidirectional Mics

 

Omnidirectional mics have the simplest polar pattern; they can detect sound equally from all directions. If this were expressed visually, it would be a circle with the mic being at the very center, with sound being detected completely around the mic and no areas where it is rejected. A classic application for omnis is a stereo pair of them strategically placed to capture a full orchestra, since typically it is desired to capture the sound of the performance hall as much as the orchestra itself.

 

Cardioid Mics

 

One of the most common polar patterns you will come across is the cardioid pattern. Named so because of the heart-shaped pattern in which it detects sound, cardioid mics are most sensitive at the front, pick up some sound from the sides, and reject sound from behind. This ability to reject sound from behind make them a favorite for situations where you are working with multiple sources and wish to isolate what is being recorded by each individual mic as much as possible. Some microphones even have what is called a supercardioid pattern, which allows for a tighter, more focused sensitivity at the front of the mic.

 

Figure 8 Mics

 

The last of the three common mic polar patterns is the figure 8. These microphones, typically ribbon mics, are most sensitive to sound at the front and back, and reject sound from the sides. As mentioned above, these are highly favored for their ability to pair with a cardioid mic for midside stereo mic configurations.

 

Microphone Accessories

 

Now that you know how to pick your mic, let’s finish up by going over some of the accessories that will help you get the most out of it.

 

About Mic Stands

 

Mic stands are fairly straightforward, but there are a few things to keep in mind to make sure you find the right stand for your needs. First, they are usually sold with either round or tripod bases. Round base stands are typically more stable, though they are not as compact as tripod stands which can usually fold down completely. If space is an issue, there are smaller table top or desk stands with both types of bases, and if space is really an issue, there are even some table-mounted stands which forgo a base altogether and can clamp to the edge of a table.

 

Second, the angle at which you need to position your mic determines the type of attachment you need at the end of a stand. If you are merely recording vocals, you can get by with just a simple straight stand. If you need to place the stand in a way that allows for more room, for example to give you space to play an instrument simultaneously, you will need a stand with a boom arm or a boom arm sold separately that can attach to your stand. Another option is a gooseneck, which is a flexible attachment that can be bent to angle the mic toward you away from the straight part of the stand.

 

Mic Clips

 

A clip is an attachment which screws onto your mic stand and holds your microphone. Many microphones come with one included that has been specifically designed to hold your particular model, but you will often have the option to purchase an additional one which may suit you better. Features may include an ability to rotate in one or more directions to better position your microphone, and most importantly, may include a built-in shockmount. A shockmount is a design feature which helps isolate a microphone from handling noise, such as vibrations or bumps to or near the microphone stand.

 

Pop Filters

 

A pop filter is a device which is typically made of foam or other sonically transparent material, and is placed between the microphone and the source. They can usually be mounted on the same stand or can come in the form of windscreens which fit over the capsule of your microphone. Typically used for recording vocals, these handy little tools reduce sudden plosives (such as those produced by making a “p” sound) to give you a more even recording. Many vocal microphones, such as the Shure SM58, have some form of protection against these sounds built into the microphone itself. But if you find you are still having issues with these sounds, you will want to reach for a pop filter.

 

Final Thoughts

 

After reading this article, you should have a decent understanding of the different types of mics out there, and what needs to go into your decision as to which is the best for your needs. I hope you have found this read beneficial, and until next time, happy reaping!

 

Support the Series

 

This course is provided free of charge, and is supported by contributions from readers. If you have benefited from this course and would like to give back to support future content for the course and others like it, please consider making a contribution in any amount by buying me a coffee through Ko-fi.

 

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