Microphones are the lifeblood of any recording studio. They are an instrument like our guitars and vocals. Microphones take mechanical energy from our vocals and instruments and converts that mechanical energy into an electric signal. Each of our three main microphone types takes this process and reacts differently to the mechanical energy fed into it. This different mechanical reaction is the result of the microphone design which produces a unique sonic signature. Dynamic, ribbons, and condensers are our three main types of microphones, each producing a different sound.
Dynamic microphones have a “moving coil” inside of them. This moving coil is attached to a diaphragm. The diaphragm is connected to a metal coil that is suspended in the center of the magnet. As the diaphragm moves back and forth, the coil moves in and out of the magnetic field, changing the polarity of the coil and creating an alternating current on the wire that is connected to the coil. This design is similar to a speaker which has a voice coil that is attached to a diaphragm or speaker cone. As current is applied to the voice coil, a magnetic field is created which moves the speaker cone back and forth to produce sound.
Dynamic microphones produce a large sound because of their design. This moving coil design is a hearty design and allows for use in high impact areas. Dynamics are used extensively in live performances. They are also popular with drums and electric guitars because of their big sound. The Shure SM57 is the most popular and common dynamic microphone that is used to record drums. It is probably the microphone that is used in most drum tracks on today’s popular music. It is also a popular microphone with guitars and the distorted guitar sound we hear in our popular recordings. The Shure SM58 is a related dynamic microphone that is used in live performances for vocals.
Dynamic microphones have a prominent upper mid range with a weaker and more grainy high frequency range. They live up to their name by being dynamic and are particularly useful for drums, guitars, and sources that have more explosive content. Dynamic microphones need large amounts of energy to get the diaphragm moving but that energy transfer creates a unique sound that is characteristic of dynamics. It is a big sound that only a dynamic can produce.
Ribbon microphones capture sound energy in a similar way as a dynamic microphone. However, instead of a moving coil connected to a diaphragm, the active element in a ribbon microphone is a thin piece of aluminum or other type of material. The metal strip or ribbon is designed between two magnets in an electrical field that is disrupted as the ribbon moves back and forth within the magnetic field inside the microphone capsule. This magnetic field dance produces the alternating current that is then transmitted down the microphone cable.
Ribbon microphones must be handled and used with much more care and attention than dynamics. The reason for this is the thin metal ribbon inside the capsule. They do not handle large amounts of energy as well as a dynamic. They had their original use in the broadcast business because of the way and manner in which they produce vocals. Two popular ribbon microphones are the famous RCA 44 and the RCA 77.
The sound of a ribbon microphone has a rolled off high end which is different from our condenser microphones. It is not rolled off in a bad way, it is rolled off in a more natural way that more closely resembles the sound we hear in real life. Ribbon microphones are more sound pressure sensitive than condensers and react differently depending on how close to the sound source they are positioned. If a ribbon is placed close to the sound source, the high end is rolled off. However, when the microphone is moved farther away from the sound generating source, the high end does not appear rolled off but more has a more natural presence with clean and clear highs coming through. Ribbons are popular with a more distant miking technique such as drums overhead or even room sound microphones. Guitars, horns, and drums benefit from ribbons because they smooth out the sometimes harsh highs that these instruments can produce. One must take extra care with the placement of the ribbon next to the sound source.
Condenser microphones have some of the features of dynamics and ribbons with new twists added. A condenser microphone is based on a moving plate and a charged fixed plate and the capacitance that is generated between them. The diaphragm of a condenser microphone is much thinner than a dynamic microphone and is treated with a metal usually gold that increases its response as a metallic plate that comes in contact with electricity. In a condenser microphone, there is a back plate placed between the diaphragm with a small distance between them. Both of these plates are then charged with an electrical current as the moving plate or diaphragm reacts to this electrical current. This back and forth process creates a capacitance that is generated between the plates and an alternating current is created. This current changes reflects the changes in capacitance and thus the sound that is characteristic of ribbon microphones.
This electrical process within the ribbon microphone occurs at a very low power level. Condenser microphones require a power source that can boost the power levels to charge the plates. Battery, external power sources, or some type of phantom power source are usually used to boost the internal mic signal.
The sonic signature of a condenser microphone is one of a more exaggerated and prominent high frequency response. There is usually a bump at the resonant frequency of the diaphragm in the frequency response of the microphone. This bump is what gives the condenser its sonic signature. Smaller diaphragms have a bump at a higher frequency which is usually less noticeable. This is due to the smaller size of the diaphragm. Condensers are most often used in the studio but can be seen in live locations as well. Condensers are known for amazing detail and clarity because of the thin and smaller diaphragms ability to react faster to sound. In the studio, they are used for drum overheads, acoustic guitars and vocals.
Our microphones in the recording and sound reinforcement process are broken down into three main types: dynamics, ribbons, and condensers with each microphone sounding like their design parameters would indicate. Dynamics are large sounding because they need lots of energy to get the parts moving and this large energy requirement is translated electronically into a big sound. Ribbons are more delicate in design and function and produce a more detailed and smooth response with clarity. Ribbons are great for vocals because they bring out the tonal variances in voice without the high end artifacts. Condenser microphones are a cross between a ribbon and a dynamic, borrowing the best characteristics from both and combining these into a unique sounding microphone that has many different applications.
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