Understanding Microphones

Quality recordings start with the right microphone choice, at least when it comes to gear. But so many of us are choosing the wrong type of microphone for the job.

In this post we are going to address the fundamentals of microphone types, so that you can be sure you are always capturing the best possible audio with the best mic for the job in any given environment. To begin, let’s take a look at the different types of microphone pickup patterns.

One of the most common forms is the cardioid pickup pattern. Cardioid microphones are most sensitive to transients, or whatever sounds are most aligned with where the microphone capsule is pointed. The cardioid polar pattern is the most common because it is effective at capturing sound only in front of the diaphragm, reducing unwanted external reflections, leakage or “bleeding” from other sound sources such as other vocalists, instruments or equipment. Although it’s primarily a choice pattern for recording vocals, some other instances where it’s application could be beneficial are when mic’ing a drum kit, live performances, and untreated rooms. This is because cardioid best isolates the desired source sound from its surrounding environment.

Some examples of popular microphones that operate with a cardioid pickup pattern are the Neumann TLM 102, Shure SM57, Sennheiser MD-421, Shure SM7B, and Electro-Voice RE20.

Next, there is the Omnidirectional pickup pattern, originally known as a “pressure” pickup pattern. Omnidirectional microphones possess diaphragms that measure sound pressure at any single point in space as they contain no specific directional information. As you can see in the diagram below, these microphones are equally sensitive to sound from all directions in any given environment. Some situations where you might find an omnidirectional pattern to be preferable are when recording the sound of a room (using as a room mic during tracking session), recording a wide spectrum sound source, recording a moving target, or when recording in stereo.

Some examples of favourable omnidirectional microphones are Boundary Mics (such as the Crown PCC-160 Boundary), Blue Bottle Rocket Stage One, and the Rode NT-45.

The third and final pickup pattern you will need to be familiar with is the Figure 8 pickup pattern. This pattern’s name derives from the shape of the pickup pattern it offers, with high sensitivity to sounds in the front and the rear, and almost zero sensitivity to sound on either side. Another way to describe this kind of pickup pattern would be to say it is “bi-directional”, because of it’s high sensitivity to sound in two directions. Sessions/shoots that involve recording two voices at the same time, recording a singing instrumentalist, or recording in stereo, are a few examples of where you might want to consider utilizing a microphone with a figure 8 pickup pattern. Figure 8 pickup patterns are most often beneficial when recording for a stereo mix, or to maximize isolation of off-axis sounds (such as isolating an instrument in close proximity).

Some examples of microphones that utilize the figure-8 pickup pattern are the Audio-Technica AT-2050, AKG C314, Coles Electroacoustics 4038, and the Behringer B-1.

Aside from the three patterns mentioned above, two additional (less common) pick up patterns that you may find yourself coming in contact within the industry are known as Hyper Cardioid, and Super Cardioid. Much like the Cardioid pickup pattern, Super Cardioid, and Hyper Cardioid are most sensitive to frequencies at the front of the microphone’s capsule, with slight alterations. Super Cardioid possesses an even narrower directional range of pickup than Cardioid, with a small bulb of rear sensitivity. Hyper Cardioid, on the other hand, has a narrow front pickup like the Super Cardioid, but offers a larger bulb of pickup range in the rear.

Finally, we can address what are known as Multi-Pattern Microphones. These are microphones that offer the user the flexibility to switch between pickup patterns while using the same microphone. Some examples of popular Multi-Pattern microphones are the Neumann U87, AKG C414, Audio-Technica AT4050, and the Neumann TLM 107. These microphones although pricey, can often offer maximum flexibility to its owners acting as a 3-in-1 (sometimes 4-in1) mic.

Now that we’ve explored pickup patterns, let’s discuss transduction. A transducer is a device that converts energy from one form to another. Usually, a transducer converts a signal in one form of energy to a signal in another. In the case of microphones, transduction specifically refers to the transformation of acoustic energy to electric energy. This brings us to the different types of microphones. There are three different types of microphones that all achieve the transduction of sound in their own unique way. They are known as Dynamic Microphones, Condenser Microphones (Large and Small Diaphragm), and Ribbon microphones.

Let’s start with Dynamic microphones. Dynamic microphones are the workhorses of the audio world. They convert sound into an electrical signal through the act of electromagnetism and can be subcategorized into two categories, moving coil and ribbon. A coil is glued to the rear of a membrane, and there is a strong magnet surrounding this coil. When sound waves hit the microphone, the membrane moves to the rhythm of the sound waves, and the coil on its back moves along with it. The relative movement of the coil within its (stationary) magnetic gap induces a small signal voltage in this coil. Ribbon microphones operate on a very similar principle, except a ribbon transducer uses a narrow strip of thin aluminum foil in place of the membrane and coil.

Condenser microphones consist of a thin membrane in close proximity to a solid metal plate. The membrane or diaphragm, as it’s usually called, must be electrically conductive, at least on its surface. The most common material is gold-sputtered mylar, but some (mostly older) models employ an extremely thin metal foil. When sound waves hit the diaphragm, it moves back and forth relative to the solid backplate. The capsule signal itself, however, is much too “fragile” to be connected to other pieces of gear. The condenser capsule’s output voltage is actually quite high, but it produces almost no current because so little energy is stored in this small capacitor. Condenser microphones, therefore, require external power known in the industry as Phantom Power. It is represented by a “V” on most industry-standard gear. These microphones possess superior sound quality and are optimal for in-studio recording.

With this knowledge in mind, hopefully you can make the right microphone choices for your next project.