Microphones – How They Work, and What They Do

Microphones. What are they and what do they do? How do I use them to get the best sound possible?

First things first – what do they do? In a sentence, they take sound waves from the air and convert it to electric signals. These signals are recorded and stored, usually digitally.

How do they do that? Generally, a mic has a diaphragm that reacts to sound waves in the air. This is converted to electricity various ways, then sent down the cable. From there, it is recorded and stored by different methods.

For a bit more in depth look at it, see this Wikipedia article.

But there are dozens of mics looking at you, waving their arms and screaming, “Pick me! Pick me!” How do you decide which one? What should be your first consideration?

Here are a few features to help you which is the best one:

  • transducer type
  • pickup pattern
  • body construction or diaphragm size
  • suitability to sound source

Also check out the Top 10 Vocal Microphone guide.

Transducer Type

The transducer is the part that converts sound in the air to an electrical signal. It's amazing how they actually do it, but there's no need to know exactly how.

It IS important to know that there are a few different kinds. Most important are:

  • condenser (also called capacitor)
  • dynamic

Most studio mics are condenser mics. They are generally more detailed, smoother, and sweeter than dynamic ones. They must have some power through the cord, called phantom power. Most preamps and mixers will supply it.

Dynamic mics are usually used in live sound. They can take more rough & tumble handling, so they're better for traveling. They require no external power.

I would recommend looking at a condenser for your first one. If you can, try to demo several to get an idea how they differ.

Pickup Pattern

The pickup pattern is the area and directions around the diaphragm that sound gets picked up from. The names for these are very weird, but here they are:

  • Cardioid
  • Omni-directional
  • Super Cardioid
  • Hyper Cardioid
  • Figure 8

The main difference is the direction that the mic is most sensitive in. There are directional styles, and omni-directional styles. (Omni means all around.) All the others pick up from one end (or 2)

What difference does this make to you? Let’s say you are recording a quartet of voices. You have 4 microphones, one for each singer. You might want to put 1 mic in front of each singer, so it picks up only him/her.

But if the mic is an omni, it will end up recording all the voices. The people beside it will "leak" into it.

If you use a cardioid, which picks up what's right in front of it, it will get right singer and not the others. You can isolate that voice from the others.

If you were recording in a big hall, and wanted to get a lot of the reverb sound from the room, you might use an omni to catch sound from all different directions.

What about a figure 8? This pattern picks up from the front and back but not from the sides of the microphone.

What is different in the super and hyper cardioid from the regular cardioids? They are still directional microphones, but are more focused in the front. The trade-off is that a small amount of rear acceptance is let in. You might say that the super and hyper cardioid patterns are steps between a regular cardioid and a figure 8.

While cardioids (and other directional patterns) have good side and rear rejection, they will still pick up that sound. It just attenuates it (makes it quieter) so you can pick a spot to accent.

So what kind should you get? If you want to do several mics at a time for an ensemble, I would go the directional route. After you have a few cardioid mics, then expand into the omni world, but always experiment.

Size of Diaphragm

This refers to whether the microphone is called a large diaphragm, small diaphragm, or medium diaphragm.

That seems fairly obvious, but it can make a difference. A large diaphragm can pick up low frequency sound better than a small diaphragm, because it can vibrate slower and has a bigger surface.

Large diaphragms are usually found in side-address microphones. This means that it is set straight up, with the diaphragm pointed out the side. It has a large body, around 2 inches or so in diameter. (See the picture on the right.)

A larger diaphragm will sound a bit fuller and warmer, due to the detail in the lower frequencies.

Audio Technica AT4050
Photo of Rode NT4 Stereo Mic

Smaller diaphragms will sound better on high frequencies, because the diaphragm can move faster. They sound a bit more detailed on the high range, but still good overall. See an example of a small diaphragm mic on the left.

Which should you get? It depends a lot on what kind of recording you want to do. Vocals usually benefit from the warmness a large diaphragm can give. Classical ensembles and drums are usually recorded with small diaphragm condenser mics.

Guitars are done with just about anything, so take your pick, or ask a friend what they use.

Suitability to Sound Source

What do I mean by that? Every mic has its own unique “sound.” Slight variations in frequency response can color the sound in subtle ways.

Some bring out the sound of different instruments and voices better than others. But one mic is never the one! There just is no Swiss Army knife microphone! You can’t have a ‘one-size-fits-all’ mic. Bedroom-Recording.com has a Top 10 list that also gives ideas for a great starter mic.

Think of using microphones like paint colors on your "canvas" of sound. Certain shades may work OK, but a slightly different shade makes the image look better. A different mic might make the sound "pop."

OK, not everyone can go out and buy a whole bunch of mics. Some kinds work well as all around workhorses. Check out the list just above for some recommendations.

When looking at specific microphones, read reviews from other people. Check what they are advertised to work with the best. See what your gut feeling says.

And have fun!

Mic Placement/Technique

Now what? Where should you put the microphone? Does it make any difference? Yes it does! Mic placement makes a world of difference! So... how do you know what to do?

Just read the page on mic placement and technique. It's part of a series on voice recording, and I recommend you look at the whole series, starting here.

About the Author Lee Weaver

Lee started his career in recording with an auspicious goal - record tracks of his own voice singing in harmony. As a hobby project, it didn't have the funding to go to a studio and pay for someone to do it for him. Like many of you, he pulled himself up by the bootstraps to learn the art of recording.

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