Types of microphones
|*||What’s a USB Microphone?
A USB mic contains all the elements of a traditional microphone: capsule, diaphragm, etc. Where it differs from other microphones is its inclusion of two additional circuits: an onboard preamp and an analog-to-digital (A/D) converter. The preamp makes it unnecessary for the USB mic to be connected to a mixer or external mic preamp. The A/D converter changes the mic’s output from analog (voltage) to digital (data), so it can be plugged directly into a computer and read by recording software. Plug in your mic, launch your DAW and start recording.
The condenser microphone is a very simple mechanical system, with almost no moving parts compared with other microphone designs. It is also one of the oldest microphone types, dating back to the early 1900’s. It is simply a thin stretched conductive diaphragm held close to a metal disk called a backplate. This arrangement basically produces a capacitor, and is given its electric charge by an external voltage source. This source is often phantom power, but in many cases condenser mics have dedicated power supply units. When sound pressure acts on the diaphragm it vibrates slightly in response to the waveform. This causes the capacitance to vary in a like manner, which causes a variance in its output voltage. This voltage variation is the signal output of the microphone. There are many different types of condenser microphones, but they are all based on these basic principles.
A dynamic mic is one in which audio signal is generated by the motion of a conductor within a magnetic field. In most dynamic mics, a very thin, light, diaphragm moves in response to sound pressure. The diaphragm’s motion causes a voice coil that is suspended in a magnetic field to move, generating a small electric current. Generally less expensive than condenser mics (although very high quality dynamics can be quite expensive), dynamics feature quite robust construction, can often handle very high SPLs (Sound Pressure Levels), and do not require an external power source to operate. Because of the mechanical nature of their operation, dynamic mics are commonly less sensitive to transients, and may not reproduce quite the high frequency “detail” other types of mics can produce. Dynamic mics are very common in live applications. In the studio, dynamics are often used to record electric guitars, drums and more.
A type of velocity microphone. A velocity microphone responds to the velocity of air molecules passing it rather than the Sound Pressure Level, which is what most other microphones respond to. In many cases this functional difference isn’t important, but it can certainly be an issue on a windy day. Very old ribbon mics could be destroyed from the air velocity created just by carrying them across a room; today’s ribbon mics can handle the rigors of daily studio use. A ribbon mic works by loosely suspending a small element (usually a corrugated strip of metal) in a strong magnetic field. This “ribbon” is moved by the action of air molecules and when it moves it cuts across the magnetic lines of flux causing a signal to be generated. Naturally ribbon mics have a figure 8 pick up pattern. You can think of it like a window blind; it is easily moved by wind blowing at it, but usually doesn’t move when wind blows across it from left to right. Ribbon mics were the first commercially successful directional microphones.