20 MAY 2017
written by Mike
In this article, I want to share with you an overview of a recording microphone. Microphones or mics are the basic instruments of capturing sounds. You have one inside your laptop, your phone and your camera. Even in a smart watch.
Before we dig deeper in microphone placement techniques and various recording tips you need to learn more about mics.
What is a condenser? Dynamic?
When you work with professionals and experienced sound engineers, you will learn that choosing the right microphone is number one thing one the list. Every audio professional will have their preferred mic, and least favourite too. Whatever you want to do you will need to understand basic characteristics of a recording microphone. So, let’s start with that.
When it comes to elemental features of a mic, three things matter.
A transducer, frequency response and directionality.
A transducer in a microphone transforms acoustic energy (e.g. your voice) into electrical energy. How a microphone registers sound depends on a type of a transducer. Two main ones are Dynamic and Condenser.
Dynamic microphones are quite cheap to build and robust.
So how do they work?
Dynamic mic operates on small electrical generator built from a diaphragm, voice coil and magnet. Let’s say you are recording yourself for a YouTube channel. The force of your voice, as a sound wave, makes a diaphragm vibrate. The diaphragm can be described as a thin membrane hidden behind microphone’s metallic mesh.
At the rear of the diaphragm is a voice coil, a coil of wire, which also vibrates. A small magnet forms a magnetic field around that wire. Physics. The movement of that coil within the magnetic field generates electrical signals that correlate to the force of your voice. Because dynamic microphones can survive in the toughest environments, they are number one choice for live performance.
It is almost impossible to overload a dynamic microphone. Good examples are Shure SM58 we use them for live sound and Shure SM57 another classic and cheap microphone. If you don’t know which one to buy you should get SM57. It will do the job.
Shure SM7B is a classic dynamic microphone used by sports commentators and radio presenters.
Have you ever wondered how is it possible that they shout their heads off, and the sound stays clear?
In most cases, Shure SM7B is the answer. My favourite dynamic microphone would also be Beyerdynamic M201. A smooth sounding mic that works great on a snare but also on some louder singers.
Condenser microphones are a bit more complicated than dynamic, more sensitive and more expensive (well, it depends…).
The basics of a condenser mic lie in a capacitor.
The force of your voice will resonate a thin metal or metal-coated membrane that sits in front of a rigid backplate. The space between the two contracts and the motion produces electrical signals.
Now, the biggest difference between dynamic and a condenser is that the latter requires additional power to run. There are two ways to power up your condenser microphone.
First one is with batteries, second, we call phantom power. Phantom power runs through the microphone cable from the interface e.g. mixing desk or audio interface. Condenser microphones are sensitive and delicate. They also produce more noise than their dynamic siblings. Maximum sound level specification means that if you shout into a condenser, there is a high probability that the recording will distort.
Good condensers are great in capturing a wide dynamic and frequency range. Try recording an acoustic guitar with a condenser and then with a dynamic microphone. You will hear that condenser will capture the smallest nuances and movements of the guitar.
A classic pair of condenser mics would be AKG 414. Sound engineers often use them as overheads for drums and choirs.
Neumann U87 is a classic studio microphone used for vocals. It is the first choice for ADR recordings or dubbings. Recording sound on sets also requires a sensitivity of a condenser. Microphones such as Sennheiser MKH-416 combine a subtlety of a condenser transducer and a robustness of a dynamic microphone. Remember also to buy a pop shield and keep an eye on a noise level.
II. Frequency response
Frequency response it the reason every music producer, sound engineer or a foley recordist has a preferred microphone. Transducer decides how the sound is captured; frequency response chooses what to capture.
Let’s say you recorded your dog. If your recording sounds 100% the same as your dog in real life, it means that the microphone that you used has a flat frequency response. It didn’t change the sound. Microphones with the flat response are used for measuring acoustics of space and can be quite expensive. Also, you don’t want to use them on your recordings.
Well, the sound of a microphone can make your recording better. It can add depth and warmth. It can capture smooth low frequencies or sharp high frequencies. It can omit frequencies that you don’t want. Some microphones will add punch to your drums or presence to vocals. Other times you may wish to use a microphone with a detailed response.
You don’t want to omit anything when recording a wide frequency instrument such as piano. Before using a microphone check its frequency response and its desired use. It’s also good to experiment with different settings.
The last one on our list is directionality.
Directionality describes the most sensitive side of a microphone. Polar patterns describe how a microphone will pick a sound and what is its best position for it. There are quite a few polar patterns to choose from, but today I will focus on three main ones.
The omnidirectional microphone will register sound at all angles. The polar pattern covers 360 degrees. It means it will pick up the sound from the back as well as from the front. With the same intensity. These polar patterns are great if you want to capture an ambience of a place, something like an inside of a cave.
Another use is to leave an omni in the room as a so-called ambient mic. You can then add this additional layer to your mix later on.
As you probably guessed, unidirectional microphones will register sounds from one particular direction more than from others. Most popular will be a cardioid, a heart-shaped polar pattern. It will pick up less ambient sound than an omnidirectional microphone, and it works great when you want the focus.
For example, if you wish to record a dialogue on set you don’t want to capture a technical crew that is chatting in the corner. Unidirectional microphones are made for this kind of stuff.
Bidirectional microphones are sensitive at front and back but omit material from their sides. They are great for vocal duets and individual stereo recording techniques such as mid-side, M-S.
This polar pattern is used when you want to dismiss unwanted sources of sound. As I mentioned before these are helpful on movie sets, during live music recordings or any environment with more than one sound source. Correct microphone placement is a skill in itself, and I will share with you some advice on that in another article.
To know your equipment is essential.
How it all works and why you want to use it?
These are the questions that you need to ask yourself before making any decision. Microphones are everywhere. You don’t have to know all the details and technical specs of their build, but don’t be ignorant. When it comes to selecting the right gear, ignorance is not bliss.