Microphone Polar Patterns

Understanding microphone pickup patterns isn’t hard, you’ve got this!

Last week, in Part 1, we looked at the basic types of microphones.

This week we get some understanding about polar patterns.

To make this real world, we are going to look at the spec sheet for the Shure SM57 Cardioid Dynamic Microphone. Go ahead and download it from this link.

We are going to look at the diagrams at the bottom of the page.

Let’s start with….

Polar Patterns

Polar patterns show you the pickup patterns of the microphone. This helps you see where to position the mic to get the sound you want to amplify and not pickup what you don’t.

If you look at the diagram, you will see marks that go from 0 degrees to 180 degrees. 0 degrees is pointing directly into the head of the microphone. Here is what that looks like.With the mic on the pattern it is a lot easier to understand the diagram.

So, the SM57 picks up the best when sound is coming directly into the head of the mic. Let’s call that 100%, the most sensitive angle on the mic. The graph has 4 lines from -20dB to 0 dB so we can divide 100% by 4 and get 25% per line on the graph.

Look at the solid line and ignore the other lines for now.

Look at 90 degrees to the left and right. The solid line crosses the 90 degree line just under the 75% line so we know the following. On the left and right of the mic, it only picks up 75% of the sound coming from those directions.

When you get to 180 degrees, directly behind the mic, the solid line crosses at almost 0dB. This shows us that the mic picks up almost nothing coming from behind the mic.

So why is this important?

With the  information in the diagram we can know that if we use this microphone for vocals, they need to be in front of the mic so you wouldn’t use this for a large group of singers. If you use floor monitors for your vocalists, you know that the best place to put a monitor is directly behind the  mic where almost nothing is picked up.

There’s got to be an easier way!

Well, yes, there kind of is.

Look at the SM57 title “Shure SM57 Cardioid Dynamic Microphone”

What’s that word ‘Cardioid’?

Well, a cardioid is a plane curve traced by a point on the perimeter of a circle that is rolling around a fixed circle of the same radius. It is therefore a type of limaçon and can also be defined as an epicycloid having a single cusp. It is also a type of sinusoidal spiral, and an inverse curve of the parabola with the focus as the center of inversion.

Right, that’s just what I thought too.

Cardioid comes from a Greek word meaning ‘heart’ because a cardioid graph looks kind of like a heart. …kind of. Anyway, it is the word used to describe the polar pattern where sound from behind the mic is rejected. So, instead of having to look at the polar pattern graph for every mic, you can get a general idea of the pickup pattern of a mic by giving it this type of name.

So we have these kinds of mics;

• Cardioid
  • Heart-shaped pattern, that rejects sounds coming from behind the mic.
• Super Cardioid
  • Cardioid, but more. It rejects more sound from the sides and picks up farther away in front of the mic.
• Hyper-Cardioid
  • Cardioid, but even more. It rejects even more sound from the side and picks up even farther away in front of the mic, but it also gets these weird pickup lobes toward the back of the mic.
• Omni-directional
  • Picks up sound equally everywhere.

So when you are initially looking at a mic, look at the pattern name (Omni-directional, Cardioid, etc.) first and look at the polar pattern to see the actual details.

Next time, we will be looking at the frequency response curve and find out how to see when a mic is perfect for that breathy vocal or the acoustic guitar.