Cardioid mic is a common choice for audio recording especially when you want to focus on the target sound and eliminate the impact of ambient sounds. In this article, we will tell you four basics that you need to know, which include:
- What is cardioid mic?
- What are its characteristics when capturing sounds?
- How to position it for single and stereo miking?
- When and when not to use it?
Video: Cardioid mic definition and audio example
Cardioid microphone gets the name because of the heart-shaped polar pattern. It is solely sensitive to sounds coming from the front and sides and is categorized as directional microphone since the direction affects the recorded sound image.
Watch the video to see how SYNCO U3, a cardioid mic for video, performs in sound pickup.
Cardioid mic diagram: Six sound pickup characteristics explained
To use the cardioid shotgun mic better, you should know how it performs in the sound pickup. Below we list six common points for you to get a general understanding.
Null point at 180°
Cardioid mic pattern is known for its 180° null point. This rear suppression of sound allows for easy positioning. Just point the mic at the source you want and away from the source you don't want.
The most common use for the 180° null point is on stage monitors. Cardioid mics perform well when placed in front of the stage monitor but pointed away. This allows singers to sing at high gain to the mic pointed at them before feedback, as the mic is pointed away and blocks audio from the monitor.
Roughly 6 dB less sensitive at 90° & 270°
So far, we have determined that the ideal cardioid mic pickup pattern is the most sensitive unidirectional pattern on-axis. We also point out that it is completely insensitive to its rear.
The sensitivity declines proportionally when the angle in the cardioid polar pattern varies to either side of 0° until we approach the rear null point. Optimal cardioid pattern has a 6 dB reduction as it is at 90° and 270°.
The cardioid mic has a 180° acceptance angle if we base our acceptance angle on the spots of -6 dB. This indicates that the mic will most likely capture sound rather reliably within 90° of its on-axis line on either side. This acceptance angle is relatively large while staying unidirectional.
Exhibits proximity effect
Cardioid polarity requires the back side of the diaphragm to be exposed to external sound pressure. This means that the diaphragm moves according to the sound pressure difference between the front and rear. In other words, the cardioid pattern is based on the principle of pressure gradient acoustics.
Microphones operating according to the pressure gradient principle exhibit proximity effects. Because the back of the cardioid diaphragm is contained in the acoustic maze, typical cardioid microphones do not exhibit as much proximity effect as bidirectional one that has equal exposure on both sides of the diaphragm.
Sensitive to vocal plosives
Exposing both sides of the diaphragm to external sound pressure also leads to sensitivity to plosives.
Vocal plosives are little gusts of wind produced by strong consonant sounds in spoken language. The plosive energy is highly transitory and can generate a significant variation in sound pressure between the diaphragm's front and back.
As the diaphragm/capsule is overloaded, this rapid yet substantial shift in pressure produces plosive "pops" to occur in the mic signal.
Excellent sound isolation
Cardioid mic excels at separating specific sound sources due to its back rejection and unidirectionality.
The broad (180°) acceptance angle of a conventional cardioid also allows for considerable tolerance in dynamic placement or mic movement relative to the sound source. We can effectively isolate a single sound source by correctly situating a cardioid microphone.
When close-miking a source with no other sound sources around or behind it, this works well. It helps if the "unwanted" sound sources are located behind the microphone, toward the cardioid's rear null point.
When properly positioned, the cardioid microphone may obtain a significant amount of gain-before-feedback in live sound reinforcement circumstances. This is because of the rear null point, which makes positioning the mic simple: direct it away from any monitors or loudspeakers.
When a microphone takes up too much sound from a loudspeaker transmitting the same microphone's signal, a feedback loop is formed. Simply angling the cardioid away from a live speaker results in great gain-before-feedback.
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Cardioid mic positioning: Single & stereo miking techniques
Cardioid mic is commonly used whether in single or stereo recording. The typical methods of placement are as follows.
Single cardioid mic placement
Listen with one ear covered and your palm cupped behind the other. Move around the sound source until the frequencies are the most balanced. When you've found the ideal spot, place the mic in that position and point its capsule perpendicular to your hand toward the target sound.
Stereo cardioid mic setup
A pair of cardioid microphones can be set up in a variety of ways to record stereo sound. Each approach serves a distinct function. Continue reading to find a setup that meets your requirements.
A/B stereo is the simplest way to set up and one of the most used methods for stereo recording.
The millisecond delay between sounds reaching each microphone rises as the distance between microphones increases. Our brains perceive the difference in arrival time as a stereo picture.
Our ears are 7 inches apart by nature. Using this separation between microphones will provide a stereo picture that sounds the closest to the recorded environment if we were standing there.
A broader stereo picture will come from spacing the microphones further apart. Experiment with this distance to see what works best for you.
A coincident pair of cardioid microphones oriented 90° to each other is used in X/Y stereo miking.
The tight spacing is said to as coincidental. For this spacing, one microphone must be somewhat higher than the other.
This method creates a restricted stereo picture and is best suited for close-miking circumstances when you use the cardioid mic for podcasting, single instruments, and spot sound effects.
To simulate human hearing, ORTF stereo miking employs two cardioid microphones. The mics are positioned 7"/17cm apart and oriented at 110°. This spacing and angle mimic the difference in arrival time as well as the acoustics of our head.
The ORTF approach generates a stereo picture that is broader than X/Y but is still suitable for mono applications. This technique is most commonly employed for capturing stereo ambiances and "soundscapes."
Cardioid mic uses: When and when not to use
As the most widely used pattern, it is likely to assist audio performance whether in the studio, on the stage, or on the broadcast site, or everywhere in between.
Best uses for condenser cardioid mic
You can use cardioid shotgun mic for streaming and many other scenarios due to its unidirectionality and backside rejection. Consider the following applications:
- Directly in front of the monitor speakers in the case of live sound reinforcement
- When high gain feedback is required
- To block background noises in a noisy environment
- To mic personal closely localized sound source
- Capture clean audio in less than ideal environments
- When proximity effect is required
- To minimize rear sound
When not to use
Cardioid mic is useful in a variety of circumstances. However, the other patterns do outperform cardioid on occasion. In the following cases, a cardioid microphone is not the ideal choice:
- If the sound source moves around the microphone
- If proximity effect is not desired
- To record the most natural ambiance
For more information about directional polar pattern, you can check the following articles:
- Hypercardioid microphone: Hypercardioid microphone: Definition, characteristics, and uses explained
- Super cardioid mic: Beginner's guide to super cardioid mic