VO Microphones Pt. 2 – Types of Mics

Three Basic Types of Microphones Explained

Microphones have a simple task.

That’s probably one of reasons I like them. Simple tools. A single speed bicycle. Well crafted steel bicycle frames. Machines which lack complexity – not because they are simplistic – but because they are focused and precise. Honed for a specific task. 

We tend to take sound for granted. It’s a much more complex phenomenon than we might realize. What we perceive as “sound” is actually an increase and decrease in pressure. Sound needs air to transmit that energy to your ears. When we pluck the string of a guitar, it makes the air around it move in the same manner. How fast that air vibrates determines the pitch. 

It works in other mediums as well – that’s why you can hear certain sounds when you are underwater -the water will still act to move that vibrational energy to you. (It’s also why in the vacuum of space no one can hear you scream).

The Job of the Voiceover Microphone

To be useful, a microphone needs to capture that vibration accurately. It does this by having a component inside which reacts to that change in pressure. This is the microphone’s “diaphragm”. All microphones have some sort of part which does this. When a change in air pressure enters the mic, the diaphragm of the mic moves along with it. That’s literally the microphone’s “ear.” The diaphragm does the same thing that our eardrum does when sound first arrives. It mimics and transmits that pressure change.  

Of course, a microphone lacks a brain to interpret those signals, so it transmits that information through its circuitry. When the change in air pressure causes mechanical movement on the diaphragm, it gets translated into a voltage signal – electricity traveling down wires. The voltage represents the change in pressure, so it increases and decreases in the same way. Since the voltage is now traveling down a wire, we can start to do things with it – making it louder, for example. Or, we can convert the voltage into digital information that your computer can deal with. Both of those occur in your voiceover studio as the signal moves through your input chain.

But, let’s keep focused on the microphone. The way a mic captures that change in pressure and what happens to the voltage is one of the places where microphones differ from one another.

While there seems to be a wide variety of microphone shapes and sizes, they can be divided into three general categories (at least the ones we are likely to encounter). 

Dynamic Microphones

Dynamic microphones have a “moving coil” design which reacts to the change in pressure. They are largely mechanical devices using a magnet and moving coil to generate a small amount of voltage. It’s actually the opposite of the way that a speaker produces sound by moving a cone. Dynamic mics do not require power, as there are no active electronics inside of them. This means they also tend to produce a low output signal. Most stage performance or handheld microphones are Dynamic designs.

Ribbon Microphones

Ribbon microphones are similar to Dynamics in that they use magnetism to transmit the signal. The difference is that the diaphragm in a Ribbon mic is a thin piece of aluminum foil which is suspended in a magnetic gap. Ribbon mics were one of the first microphone designs (those big square RCA mics you see in the set photos from radio dramas were typically ribbon models) and they have some interesting characteristics. They also have an inherently lower output (though there are newer models which contain amplifier circuitry and are called “active” ribbon microphones). 

Condenser Microphones

Condenser microphones work through capacitance rather than magnetic response. To keep things simple, think of a capacitor as two pieces of metal in close proximity to one another that produce varying amounts of electricity as their position changes. In a Condenser mic’s capsule, the moveable diaphragm is actually paired with a non-moveable back plate. When sound hits the diaphragm it gets pushed closer to the back plate, which changes the amount of charge produced. This varying charge provides the output signal. Because the capsule and electronics inside these need power, Condenser microphones require voltage. They tend to be much more sensitive to changes in the sound source and have a higher output signal.  

Which Microphone Type is Best for Voiceover?

That sensitivity and robust output translates into greater detail and less need to amplify the signal. The potential downside is that It does create a more fragile device. However, most of the recordings we tend to do for voiceover take place in an indoor location under relatively controlled circumstances. 

Given those choices, the type of microphone generally chosen for voiceover work is a Condenser microphone. Further, we tend to prefer a Large Diaphragm design for its ability to accurately capture the nuance of spoken word performances. In other words, a Large Diaphragm Condenser (LDC).

Next, we’ll figure out why those LDC’s all sound a little different from one another…

Microphone Basics – Microphones Pt. 1 – can be found here.

Types of microphones – Dynamics, Ribbon, & Condenser – Microphones Pt. 2 – can be found here

Condenser microphone capsule designs – how that influences sound quality – Microphones Pt. 3 – can be found here.

What exactly makes a “good” microphone for VO? – Microphones Pt. 4 – can be found here.

Recommended USB Microphones for VO – Microphones Pt. 5 – can be found here.

Recommended XLR Large Diaphragm Condenser Micrphones for VO – Microphones Pt. 6 – can be found here.

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