For the past few weeks, I’ve been going to a recording studio in town and filling my brain with audio engineering information. It’s pretty awesome.
I find it easiest to cement said information in my brain by regurgitating it in writing form, so I wrote down a bunch of notes and info and stuff…and then I thought to myself, “Hey self. I have a blog now, which means that my own regurgitated information can now be published for the world to see!”
I got so excited about this realization that I didn’t stop to ask myself if the world would want to see it, but it’s too late for that now.
So today’s post is about……………
Sweet dance moves! No, just kidding. Today, blog reader, we will be learning ALL ABOUT MICROPHONES.
Microphones, you may say to yourself, are really boring. But you’d be wrong.
A simple definition of a microphone is this: a device that converts sound pressure variations in the air to voltage variations in a wire (an audio signal). Although this transduction is ideally as transparent as possible, any microphone will color the sound slightly as it’s being used.
Ok, so that does sound pretty boring. Think of it this way: microphones are the ears of a studio. They’re the magical vessel that allows Drake’s sweet, sweet voice to reach your eager ears during a live concert. They’re the beginning of a musical recording journey. They’re the wind beneath your wings.
Types of Microphones
Since there are many different types of microphones in the world, we’ll focus on two that are used commonly for music.
Dynamic Microphones are often used in onstage settings because they have a small area around the mic that picks up sound (more on this in the “polar pattern” section), which is useful in loud settings. It is also rugged, so it won’t break as easily if dropped or used as an impromptu hammer.
You’ve probably seen one. Here’s an example:
Dynamic microphones don’t need external power–also a plus for live settings where you’re moving around a lot.
Condenser Microphones are usually used in studio settings as they are more sensitive both physically and in the sound they pick up. They need external power (AKA phantom power). If you are onstage, condenser microphones can be susceptible to picking up their own sound from the monitors and re-amplifying it, in an endless and cringe-worthy loop known as feedback. Feedback sounds like this: EEEEEEAAEEAEEEEEEEEEEEEAEEEEAEEE. Avoid feedback. And don’t drop a condenser mic. It will break, as will your heart.
There are other differences between these two mics that we’ll get to later.
The frequency response of a microphone shows which frequencies are amplified or attenuated (lowered) when using the microphone.
Different frequencies, to our ears, sound like different pitches. Low frequencies sound like low notes, like the the big thumping bass beats in dance music. High frequencies sound like high notes. Like a flute or a small screaming child.
Our ears can hear sounds somewhere in the 20-20,000 Hz range and human vocals hang out somewhere around 5,000 Hz.
Dynamic Microphones have a frequency response that’s usually designed for vocals. The frequency response of the SM58, a common dynamic mic, looks like this:
Notice how it looks a little like this illustration from Antoine de Saint-Exupéry’s The Little Prince of a Boa Constrictor that has just eaten an elephant:
Anyway, the frequency response peaks at about 5000 Hz, where the average human vocals are, and rolls off in the lower frequencies, which muddy a vocal performance.
Condenser Microphones are usually designed to pick up a more transparent audio signal, so their frequency response (that of the AKG 414, a common condenser mic) looks more like this:
It is much more flat across all frequencies, picking them up equally. Note: apparently it’s a really, really tough engineering trick to make a microphone’s frequency response completely flat. Bravo microphone engineers for getting pretty darn close.
Some microphones have different frequency responses than these two, because they may be designed for a specific instrument like a guitar, saxophone, or cowbell*, which have different frequency output patterns.
*Disclaimer: No microphone yet exists that is designed specifically for cowbell.
Microphones also differ by the polar patterns they have. A polar patter is basically an imaginary bubble around the microphone’s head that shows where the microphone is most sensitive. For example:
Dynamic Microphones like the SM58 have a cardioid, or directional, polar pattern that looks like this:
It’s called “cardioid” because it’s supposedly heart-shaped. I’ll leave it up to you to decide if it looks more like a heart or a butt. Moving on.
As you can see, it hears most strongly directly in front of the microphone and rejects the signal directly behind it. Again, this is ideal for most live settings, because you don’t want the screams of adoring fans who are standing behind the microphone to be amplified above the actual singer.
Condenser mics like the AKG 414 can have a few different polar patterns that you can usually switch on or off on the microphone itself.
An omnidirectional polar pattern picks up signal equally from all directions. It captures the truest, most accurate representation of sounds in a room and is often used in classical music performances, because classical musicians want as close to the “true” sound of an orchestra in a room as possible. Its polar pattern is a circle (or in reality, a globe):
A figure 8 oriented mic picks up sound equally in front of and behind the mic, but rejects sound on the sides. I have no idea why it’s called a figure 8, so let me know if you have any explanation. It looks like this:
Those are the basic polar patterns of most mics you’d use in a studio or live setting.
There are other patterns that start to look pretty crazy like the one from a shotgun mic, which is used to pick up very narrow or specific sources of sound while rejecting any surrounding noise, like you’d want for recording dialogue in a movie.
Here’s a picture of me expertly modeling a shotgun mic with a fuzzy thing around it to block wind noise (called a dead cat–no joke).
Using a Microphone
When choosing a mic, it’s easy to get caught up in the technical specifics. In reality, the acoustics of a room and the placement of the mic are often more important than the small differences in tech specs.
Here are some super simple things to think about:
- Place a microphone where the instrument sounds best. This seems obvious because it is. An acoustic guitar sounds different near the sound hole than near the frets.
- Think about what kind of sound you’re going for. An omnidirectional mic will have more “room sound” whereas a dynamic mic with a cardioid polar pattern will be better at isolating a single instrument or voice.
- Sing into the front of the microphone and not the back.
- Don’t use the microphone as a hammer, even if it’s a dynamic microphone and especially not when it’s being amplified.
There is a lot more to know about using microphones, such as their role within the signal flow of your whole setup. Mics are just the first step in the recording or amplifying process and there’s a whole bunch of technical stuff to get right between singing into a mic and hearing it on the other side.
But this post is already really long, and I’m still a newbie at all this. So I’ll leave you here with JT and his mic and his angelic voice that you can imagine in your head.