I often get asked, "What is the difference between a Shure SM58 and a Shure Beta58?" Well, apart from a pile of cash, they have different characteristics. The first characteristic we are going to look at is the Directionality of microphones. Every microphone has a specific Pick-up Pattern or Polar Pattern. As we will see, this has nothing to do with the snowy imprints of large, white, seal-eating bears!

Directionality

Not all microphones pick up sound from different directions equally. Some microphones are designed to pick up sound from all directions, others are designed to pick up sound from the front and sides, whereas others are designed to pick up sound from the front and back. So we say that a microphone has a Directionality.

Nearly all microphones fall into one of four categories where directionality is concerned:

• Omnidirectional,
• Cardioid or Unidirectional,
• Hyper-cardioid or Super-cardioid, and
• Bi-directional or Figure-of-Eight

Each type of directionality can be shown with a diagram and this diagram is called a polar pattern. The polar pattern diagram is easily expressed as a symbol and this symbol is usually printed on the side of the microphone! We are going to look at each type of directionality, learn the symbols on the microphones and explain why we need microphones with different polar patterns!

1. Omnidirectional Microphones

Omni (means all) and so Omnidirectional microphones pick up sound from all directions. This is shown in the polar pattern like this:

Omnidirectional (Omni means all)

Clip-mics - usually clipped to a shirt or lapel of presenters on stage or television - are omnidirectional. They pick up sound from all directions. It does not matter which way the microphone appears to be pointing - the sound pick-up is the same. However, they are susceptable to wind noise (the noise created by breath hitting the diaphragm of the microphone) from one direction. To prevent this, clip mics are often clipped upside-down so the top of the microphone is pointing away from the mouth of the person!

Because omnidirectional microphones pick up sound from all directions, they are particularly susceptable to picking up the sound from loudspeakers or stage monitors and this can cause feedback.

2. Cardioid or Unidirectional

Cardioid literally means heart-shaped and describes the polar pattern as we can see in the diagram:

Cardioid

Cardioid microphones are sometimes called unidirectional. This means they mostly pick up sound from one direction (the front), some sound from the sides, and none from the back. It is by far the most common type of directionality found on stage microphones. The Shure SM58 and Behringer XM8500 both have Cardioid pick-up patterns.

Because Cardioid microphones do not pick up sound from the back, they are used where the sound amplification is coming from in front of the performer, such as stage monitors or front-of-house speakers. I'll say more about this later in the article.