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Omnidirectional microphone and unidirectional are the two common terminologies you will come across when stepping into the business.
In fact, it is about the directionality of a microphone. It refers to whether the microphone picks up audio from the front only or from all sides and is always known as the polar pattern of a mic.
Polar pattern is also called pick-up pattern, because it is the function to “pick up” the sound. In this article, we will try to remove some of your confusion and tell you the difference between omnidirectional vs. unidirectional. We hope then you will be able to make a more informed decision.
The prefix “omni-” comes from Latin and means “all”. In this way, an omni directional microphone captures sound equally from all directions. This means that whether you’re in front, behind, or on one side of the mic, it records the signal with equal strength.
The omni microphone is always great in situations where sound needs to be detected and recorded from different directions or locations. Those used very close to the source, such as lavaliers, headsets, and earsets, are usually omnidirectional mics.
Like “omni”, the prefix “uni” comes from Latin, but it means “one”. This type of microphone, also named as directional microphone, picks up sound from the top of the microphone. It is an approach to pick up sound from only one direction, very little from the sides, and almost none from the back.
The pickup pattern of the unidirectional mic is often heart-shaped. For this reason, this type of microphone is also referred to as cardioid mic. It usually takes a certain amount of skill and practice to use a unidirectional mic.
Omnidirectional vs. unidirectional microphone
An omnidirectional microphone is commonly used for television shows and in concerts when the audience are expected to hear sounds from multiple directions. As we earlier mentioned, an omnidirectional mic gets signals from all sides.
A unidirectional mic will pick up less than 50% as much sound from the sides as from the front, and less than 10% as much sound from the rear. This is a guarantee of more quality sound and less unsought sound.
In addition to the said difference in polar pattern, here are the distinctions between unidirectional microphone vs omnidirectional.
Leakage: In a multi microphone setup, omnidirectional microphones may not be an ideal choice. “Leakage” seems to be the buzzword that is often be heard in such situations and unidirectional mics would be the perfect choice. However, an omni directional mic would often provide a better performance, because of its less vibration-, handling-, popping-, and wind-noise, and no bass buildup. They can be even used right side up or upside down - this is a typical feature of omnidirectional lavalier microphones.
Channel separation: Compared to a unidirectional microphone, an omni mic usually has less precise channel separation, because it picks up sound from all directions. Hence, if channel separation is a need, then the ratio between indirect and direct sound may be a disappointment using omnidirectional microphones.
Low frequency response: Omnidirectional condenser microphones have in general a more extended low frequency response and lower distortion over directional microphones in a considerably longer distance, say, a figure of over 30 cm.
Proximity effect: This is the biggest difference between omnidirectional vs cardioid. Professional omnidirectional microphones do not exhibit the effect and directional mics hold it to make changes in frequency response so that they could attach emphasis to lower frequencies. This is also the reason why microphone omni directional is generally not recommended for live sound.
Wind- and pop-noises: These are commonly existing problems when using directional microphones which, due to the inbuilt more compliant diaphragms, are more sensitive to wind and pop noises than omnidirectional microphones.
Distortion: Directional microphones tend to distort more than omnidirectional microphones, which is especially important when working with high SPL's in close miking situations.
When should they be used?
Omnidirectional mics are widely used in broadcasting and other professional applications when it is desired to pick up some ambient sounds on the spot to add the sense of aliveness to the whole recording.
Basically, quality omnidirectional microphones are ideal for:
Recording in stereo
Recording a moving target
Recording a wide sound source
Recording the sound of the room
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.
Basically, cardioids are ideal for:
Picking up sound in untreated rooms
Miking up a drum kit
In the previous article Top 5 things you need to know about omnidirectional microphone, we made it clear about what is an omnidirectional microphone. In this article, we try to find out the differences between unidirectional and omnidirectional microphone. However, all this is just the basis for you to select a microphone. We strongly recommend that you could also be able to get aware of the operational differences. This probably is the way for you to get the maximum out of the microphone.