Excerpted from our “Home Studio Series” Volume 4, The Home Studio Microphone Guide.
Different types of mics are categorized by the type of element used. The most common mics used in an audio recording situation are condenser, electret (condenser), ribbon, and dynamic. Differnt mics also have various pickup patterns (or polar patterns), which refers to breadth of a microphone’s area of concentration. In other words, it refers to how sensitive the microphone is to picking up a sound source relative to it’s central axis. Most mics have a fixed pattern, though many studio mics include a range of pickup pattern choices, typically by way of a switch on the mic.
(Polar Pattern images © Galak76) • click on the images to enlarge
An omnidirectional pattern will pick up 360 degrees around its element. While it picks up sound sources equally from every angle, you may find that there is a slight flattening of the response from sources coming in from the back of the microphone. But if you have one mic and you want to pick up everything going on in the room, like a choir or a circle of singers or strings, an omni mic setting is the one to use.
A bi-directional (or Figure-8) mic will pick up sound sources equally from the front and back of the mic. A bi-directional mic has two elements, one is negatively charged and the other positive. Most ribbon microphones have a bi-directional pattern, which is useful if you have two sound sources you want to record, like a duet of singers or instruments.
Cardioid is a tighter pickup pattern, and gets its name from the heart-shaped pattern seen in the diagram. The most popular mic pickup pattern, cardioid mics will pick up sound sources in a fairly wide range from the front of the mic, will taper out sources not directly in front, and have almost no sensitivity to sounds coming directly from the rear of the mic. This helps reduce feedback and focuses on the sound source.
Compared to a Cardioid pattern, a hyper-cardioid microphone has a tighter area of front sensitivity plus a small area of rear sensitivity. A hyper-cardioid microphone is not unlike a bi-directional, but with a larger area of concentration in the front and a smaller area in the back.
A shotgun mic is a unidirectional mic designed to pick up things that are far away, with a high degree of focus, so as not to pick up sources it isn’t directly pointed at. They’re typically electret condensers, and are often used for TV and field recording, though they can be used to isolate instruments in a studio setting, like a bass drum or piano.
Pressure Zone Microphone (PZM)
PZMs have a very specific place, and are not typically used in studio recordings (of course, there are exceptions). Most often, a PZM is an omni-directional mic mounted to a plate, so that the mic picks up all the reflections of the sound in an awkward space (e.g. inside a closed piano).