Microphones

Types of Microphones

The Dynamic microphone is probably the most popular type of microphone. This is probably because it’s somewhat inexpensive to manufacture as well as being very rugged and reliable. Many beginner microphones are dynamic type. They are great for voice and vocals and work well in live situations. For instance if you drop a dynamic mic on the floor from about 4 feet or so it will probably survive and still work, never mind the dented windscreen. You can’t really do that with most condenser or ribbon mics. Dynamic mics also work will for percussion and drums. One of the better sounding snare and tom mics is the Shure SM57. It can take a beating, literally, and keep on working.

Dynamic mics work just like a speaker works but the other way around. A speaker translates electrical energy into acoustical energy while a mic translates acoustical into electrical. This is because both use the same design and principle of operation. It’s basically a diaphragm is attached to a coil of wire. The coil of wire is mounted next to a magnet but allowed to freely vibrate (sounds like a speaker as well). Sound, acoustically, strikes the diaphragm which causes it to resonant (vibrate). This vibration moves the coil of wire between the magnet which breaks the magnetic. This causes a small electrical current to occur and be sent out the taps on the coil of wire. Some good dynamic mics are the Shure SM57 and SM58 they sound great for voice, drums, guitars, and just about anything else.

Condenser microphones are another very popular type of microphone. These mics are usually less rugged than the dynamic and are used for studio work. There are some however that have been made especially for live on the road work. The condenser mic has really come a long way in recent years in terms of durability and reliability. It’s made of gold covered plastic diaphragm attached to a conductive backplate. The backplate is usually made of a gold plated ceramic material. It operates similar to that of a capacitor. The diaphragm and backplate is separated by small amount of space (air) and are somewhat close to one another. This is what forms the capacitor or condenser element. An electrical charge is placed on the diaphragm which polarizes it. This is why most condensers require phantom or battery power to operate. When sound makes contact with the diaphragm it causes the electrical charge to change. These changes are the electrical equivalent to the sound. There main benefit to the condenser is it doesn’t have to move a coil of wire bur rather a very light weight plastic diaphragm. The condenser element produces a very small amount of current and needs to be buffered using a high impedance circuit namely an amplifier. The amp not acts as an amplifier but also as an impedance translation device otherwise any load placed on the mic element will drain it. Currently there are a number of types of amps which are usually placed inside the mic. Op Amps are used as well as discrete transistor designs. Some of the earliest condenser element mics actually used a tube and were somewhat larger in design. These mics are usually more susceptible to temperature and humidity changes and aren’t usually the best for live performance with a number of exceptions. For voice and vocals the Shure Beta 87A Condenser is a wonderful mic for both live and studio work. Another great lower cost condenser is the AKG C 414. The Neumann TLM 103 is an excellent mic for voice and acoustic instruments. There is a dual-element microphone made specifically for kick drums: Audio Technica AE2500

The Ribbon mic is another type of microphone that has special uses and is really a Studio-Only type of microphone. They are usually used for vocals and acoustic instruments because of their sensitivity, warm natural sound, and transient response. These mics are more fragile than that of Dynamics and Condensers. They operate in a similar fashion to that of the Dynamic in that it breaks the lines of the magnetic field but instead of using a coil of wire attached to a diaphragm the diaphragm itself is used. The diaphragm is actually a thin corregated metal plate that looks alike a ribbon. This metal plate or ribbon is stretched between a magnet and secured at the non-polarized ends. The ribbon is placed very close to the magnetic with a very small air gap. When sound hits the ribbon it causes it to vibrate and break the magnetic field which produces a small electrical current. Here again the problem of amplifying this small current comes into play. Usually an isolation transformer is used to raise the impedance of the ribbon element as well boosting the voltage of the signal. Some of the more widely used ribbon mics are the Royer R-121 and AEA R84. There are some lower cost alternatives on market that offer some of the same advantages: Nady TRM-6 Tube and the Electro-Harmonix EH-R1.

Pressure Zone Microphones are one of the newer types of mics. They are also called PZM which is a trademark of Crown. They offer a wide range of uses including miking large orchestras and recording single instruments. They are omni-directional and do not suffer from bounced sound waves that come off of the walls. They are very durable and can handle a large SPL sometimes greater than 150dB. This makes them very useful for studio work. You may have seen them and even wondered if it was actually a mic. They are flat and square. The plate is used as a reflective surface with the mic element placed very close to and facing. The element detects pressure changes that are created when sound enters the small air gap between the mic element and the plate. The size of the plate itself also determines what the lowest frequency it can detect.