When recording loud instruments with particularly high sound pressure levels, you want to ensure your microphone can handle the SPL (sound pressure level) without causing major distortion or ruining your equipment. Hence the purpose of the Dynamic Microphone.
What is a Dynamic Microphone?
Often considered the workhorse microphones of the recording world, dynamic microphones contain a diaphragm made up of an electromagnetic structure in which sound waves are converted (via a transducer) into electrical signals. These electrical signals are then able to be processed through the board or outboard gear and onto your recording device. The sound is captured from the top of the microphone, and almost all dynamic microphones have a cardioid polar pattern.
Dynamic microphones are not as sensitive to noise as condenser microphones. This decreases the chances of distortion that can easily occur when using a condenser microphone with loud SPL sound sources. Dynamic microphones do however require some sort of a preamp because they do not contain their own amplification stage.
The ability of dynamic microphones to handle loud SPL (sound-pressure levels) is due to the structure of the transducer, which consists of a small coil of wire attached to a diaphragm and suspended in between two magnets, creating a magnetic field. As sound hits the diaphragm, the coil vibrates and creates an electric signal. The dynamic microphone’s ability to create its own electric signal differs from the condenser microphone, which needs an outside source of power (phantom power) to create an electrical signal.
Dynamic Microphones are subject to what is known as the proximity effect. The proximity Effect occurs when the bass response of the microphone is dependent upon the closeness of the sound source to the diaphragm of the microphone. The closer the sound source is to the diaphragm, the higher the bass response of the microphone, which will provide you with a “boomier” sound or an increase in the low frequencies.
Dynamic Microphones are less expensive than condenser microphones and do not require phantom power. They are great for loud vocals and drums and for use on guitar and bass amps. Popular dynamic microphones include the Shure SM57 and SM58, which are often used for live sound. Senneheiser 421s are a staple microphone for toms but sound great with any electric instrument or live sound. The AKG D112 is used for kick drums and bass guitar amps because it is great at capturing low ends. The Shure SM7 is a common radio mic but sounds awesome on any vocals. The SM7 was the vocal mic used on Michael Jackson’s Thriller album. There is a very good chance you have heard all these microphones before on some of your favorite albums.