Unidirectional vs. Omnidirectional Microphones - What's the difference?

Unidirectional microphone vs. omnidirectional, which one is better? They are the two most popular terminologies you will come across when shopping for microphones.

If you’re facing a dilemma of choosing between unidirectional and omnidirectional microphones for your project, don’t feel troubled, many people are faced with the same problem. 

You should not assume that omnidirectional microphones are the ideal and default choice for most types of project.

In this article, we will help you learn the difference between the two in order to remove any confusion. This way, you will be able to make a more informed buying decision.           

Unidirectional and Omnidirectional Microphones Explained

The two most popular types of microphones these days are omnidirectional and unidirectional. They have different abilities to pick up sound from varying directions. 

Omnidirectional Microphone

This type of microphone picks up sound in all directions, but that also means it has no particular pickup pattern. Imagine you are a member of a singing group and the group is standing in a circle. You could hold the omnidirectional microphone at the center of the group, and all voices would be collected at the same volume.

Unidirectional Microphone

This type of microphone picks up sound from the top of the microphone. Basically, it picks up sound from only one direction, very little from the sides, and almost none from the back. This type of microphones must be pointed at the source of the sound.

You might want to think of the pickup pattern of the unidirectional mic as being heart-shaped. For this reason, this microphone is also referred to as cardioid mic. Usually, it takes a certain amount of skill and practice to use a unidirectional mic.

How Does a Microphone Work?

Though microphones have their differences and different uses, they are all transducers. They convert sound waves to an electrical signal. The dynamic microphones are the most commonly used. They work using electromagnetic induction.

Sound waves hit a thin diaphragm, which causes it to move. The diaphragm is attached to a coil, surrounded by a magnet. The magnet creates a magnetic field around the coil. The sound waves move the coil, creating an electrical current (sound signal).   

Unidirectional vs. Omnidirectional Microphones

Omnidirectional microphones are most often used in surround sound environments, and are commonly used for television shows and in concerts. As we earlier mentioned, an omnidirectional mic receives signals from all over.

As a working estimate, a unidirectional mic will pick up less than half as much sound from the sides as from the front, and less than a tenth as much sound from the rear. This provides you more quality sound and less unsought sound.

In a multi microphone configuration, omnidirectional microphones may not be the ideal choice due to leakage. A cardioid mic may be the perfect choice for a multi microphone setup; however, an Omni mic usually provides a superior performance.

In this case, omnidirectional microphones are considered a better choice because they feature: less wind noise, less popping, no bass buildup that is usually caused by proximity effect, less vibration noise and handling, and they can be used right side up or upside down.

Channel separation is usually less precise with an omnidirectional mic compared to a directional microphone. This is so since Omni microphones pick up sound from all over. So, if channel separation is desired, then the ratio between indirect and direct sound may be disappointing with omnidirectional microphones.

Unidirectional microphones do normally feedback at considerably high frequencies. On the other hand, most omnidirectional microphones feedback at bass or lower mid-range frequencies.      

What Occasion Should They Be Used?

A unidirectional microphone is mostly ideal as a recording microphone for vocal applications and live recordings. It is the perfect choice when the acoustics of the recording environment are good. A cardioid mic will discard audio from behind, ensuring that there is minimal effect from unpleasant audio.

Basically, cardioids are ideal for:

• Picking up sound in untreated rooms
• Live performances
• Miking up a drum kit

The major drawbacks for using directional microphones are:

• Off-axis coloration
• Sensitive to pop-noises and wind
• Proximity effect

Omnidirectional microphones are widely used in broadcast and other professional applications. They are the best for on-camera interviews because you do not have to worry about pointing the microphone.

Many of the microphones used by television and radio reporters are omnidirectional because it is usually desirable to pick up some ambient sounds in the field to add to the broadcast’s sense of aliveness.   

Basically, omnidirectional mics are ideal for:

• Recording in stereo
• Recording a moving target
• Recording a wide sound source
• Recording the sound of the room

In Conclusion

When comparing unidirectional vs. omnidirectional microphone, you should be able to identify as well as highlight the operational differences each is best suited for. You can easily achieve this by understanding their inbuilt polar pattern design.

A few things to remember about the omnidirectional mics are: all-round pickup, no proximity effect, low handling noise, low sensitivity to explosive audio, not much isolation, and pickup of room reverberation.

A few things to remember about the unidirectional mics are: selective pickup pattern, coincident stereo miking, superior gain-before-feedback, bigger proximity effect, good isolation, and reflection of leakage, background noise and room acoustics.