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3.3 Microphones

Talking about which microphone to use for a particular application is a minefield, because everyone has opinions. In this lesson you will learn about a few different microphone types and get some recommendations on what to use.

3.3 Microphones

Talking about what microphone to use for a particular application is a minefield. Because everyone has opinions. In this lesson, you will learn about a few different types of microphones and get some recommendations on what to use. When it comes to microphones, there are a ton of options. Just one microphone company makes about 18 different large diaphragm condenser microphones, it's absolutely crazy. Before we get into drilling down into what you want to look for, let me first explain about the different types of microphones. Microphones convert acoustic energy, sound, into an electrical signal. The topic of microphones is complex and for this course we're going to focus on a few basic types of microphones. Microphones are often referred to by how they work. Dynamic, condenser, or piezo, and by their directional characteristics, cardioid, omni, shotgun. Two of the most common types of microphones are dynamic and condenser. Dynamic mics are highly dependable, rugged, and reliable. Dynamic mics function just like a speaker, only in reverse. There's a small moveable induction coil positioned in the field of a permanent magnet, and the coil is attached to a very thin diaphragm. When the sound waves move the diaphragm, it moves the coil in the magnetic field, generating a small electric current. This electrical circuit is the microphone's output. Because of their construction, dynamic mics are very common for stage use, where rigidness is important. But they're also widely used in recordings as well. Dynamic microphones in general have a more limited frequency response compared to condensers. A condenser microphone uses a thin conductive diaphragm held close to a disc called a back plate. This arrangement basically works like a capacitor, when sound pressure acts on the diaphragm it vibrates slightly in response to the wave form. This causes the capacitance to vary which causes a variance in the output voltage. This variation is the signal output of the microphone. Condenser microphones are different than dynamic microphones for a few reasons. The diaphragm element is much lighter than a dynamic microphone so it can respond very quickly to sounds. Because of this faster reaction time the sound is said to be more transparent and condensers are far more accurate than a dynamic microphone. Because of their construction and electronics condensers are not as resilient to physical shocks and humidity compared to dynamic mics. Condenser mics have excellent sonic characteristics and are widely used in recording and live productions. All condensers require power, as they have electronics inside to make them function. Some condensers use a battery, but more often they will use something called phantom power. Phantom power in the context of professional audio equipment is a method for transmitting DC electric power through microphone cables to operate the active electronic circuitry. There are a few other microphone types, like ribbon and piezo. Piezo microphones are pressure sensitive and are sometimes called a contact microphone. Piezos are almost completely insensitive to air vibrations, so they are not appropriate for voice. A ribbon microphone works a little bit differently. An extremely thin sheet of metal, or nanofilm, of electrically conducted ribbon is suspended within the field of a permanent magnet. When vibrations hit the ribbon, it creates voltage by electromagnetic induction. Ribbon microphones sound fantastic. And they were the standard for recording and broadcast from about 1920 to 1950. However, ribbon microphones are very delicate, and they usually require a lot of preamplification compared to dynamic microphones and condensers. So they're not recommended. You are going to want to stick to dynamics or condenser microphones. All microphones have a polar pattern that indicates how sensitive it is to sound coming from different directions. An omnidirectional pattern responds to sounds in nearly all directions. A cardioid pattern looks like a fat heart, and rejects sounds from directly behind the microphone element. Supercardioid and Hypercardioid have a more narrow pattern in the front of the microphone, but start to accept sounds coming from the rear of the microphone element. A shotgun mic's pattern is very narrow in front, and has a narrow response from the rear, but does a good job of rejecting sounds from the sides. For recording voice overs, you are going to want to stick to cardioid or perhaps shotgun pattern microphones. Because we wanna use that directionality to reject any ambient noises and room reflections in your space. Knowing about the polar pattern in a microphone is important because it will help you decide if the microphone is appropriate for what you are trying to record. Directionality in a microphone can be a good way to focus in on your sound source. But directionality also causes something called proximity effect. The proximity effect in audio is an increase in the bass or low frequency response when the sound source is close to the microphone. This is good to know, because it can help with some sound sources, and it can make other sound sources a nightmare to control. This is a recording of the AKG C3000B large diaphragm condenser microphone from about 12 inches away. This is a recording of the AKG C3000B large diaphragm condenser microphone from about four inches away. All of these microphone types and patterns will sound slightly different but those differences can sometimes be very subtle. Some microphones are thought of as being more appropriate for certain types of voiceovers. For example, a radio announcer might use a big dynamic microphone and record with it really close for that fat, rich, broadcast sound. A movie trailer voiceover might use a shotgun microphone for that super, in-your-face, hyped sound. If you are just starting out, and you want a great all-around microphone, I would recommend a large- or small-diaphragm condenser microphone. You can get all of those same types of styles from a large or small diaphragm condenser microphone, but you won't be locked into anything specific. A few dynamic microphones have a nice, natural sound and are great for voiceovers, but dynamics have less output compared to condensers. So they will need to be amplified more and this might push a pre-amp up to where you might here some noise. Condensers on the other hand have a nice juicy output so you wont have to push them as hard and as you will see you can get very good results from an inexpensive condenser microphone. In the next lesson, you are going to learn about some of the differences between large and small diaphragm condenser microphones. And here's some examples of these mics in action.

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