As a singer, I have used countless mics, testing, and comparing them. Yet, I like cardioid mics among the different mics. This is because of its unidirectional polar pattern. But what is a cardioid microphone? Well, a cardioid microphone is like all other microphones because it picks up sounds.
The difference lies in the way it picks up sounds. From the front and both sides, it picks up sounds with high gain. But it picks up poorly the sound coming from the rear. Thus, it is good to use if you want to pick up the front and side sounds. If you’re going to record your performance, for example, and your audience is at the back, you should use a cardioid mic. This is because the mic will not pick up the noise created by your audience.
Features and Characteristics of Cardioid Microphone
There are specific characteristics and features of cardioid microphones that are worth noting. First, it has a standard unidirectional polar pattern. This means it has a null point directly to its rear, which is 180° from the front. Moreover, it is the most common mic used in studio, broadcasting, and stage. Plus, its sides are less sensitive to sounds. It is around 6dB less sensitive at its two sides.
The cardioid mic’s reception of sound is quite good because it exhibits a certain proximity effect. It is as if you are very near the mic. Moreover, it shows excellent sound isolation. Thus, if you use it in recording, you don’t need to worry so much about unwanted sounds coming from the rear and sides.
The Cardioid mic is also perfect for use if you are recording a single sound source. This is because it exhibits the property of gain before feedback. Hence it is often used in near-coincident and coincident stereo way of utilizing mics. Moreover, it tends to become more directional as the sound frequencies increase. Yet, it is less directional with lower frequency sounds. Plus, it works using the principle of pressure-gradient.
Cardioid Mic Polar Patterns: Testing the Gain of the Cardioid Microphone
If you want to test the gain of this mic, you can record sounds while rotating the microphone. Start rotating the cardioid mic from 0 to 360 degrees. You will discover that as the mic rotates, the gain it records vary. This is because the mic is unidirectional.
If you are going to look at the polar plot response of a cardioid mic, you will discover that it is shaped like a heart. Hence, this mic is called “cardioid” from the Latin word Kardia which means “heart.” It is highly sensitive to the front and side sounds but is almost insensitive to the rear sounds. So, if you only want to pick up sounds from the front and sides, you should use cardioid mics.
If you have a home studio, for example, you can use a cardioid mic to get rid of rear noise. It is very sensitive to those sounds that come on-axis, directly in the face of the microphone. Thus, with the use of this mic, you get an in-your-face sound recording. This mic, of course, is relatively sensitive at 90° and 270°. Aside from being referred to as cardioid, it is also sometimes referred to as kidney, unidirectional, or heart.
Different Types of Cardioid Microphones
The microphone technology has dramatically evolved since its invention. Cardioid microphone, for example, was invented when audio engineers discovered that they could combine omnidirectional and pressure gradient microphones. This combination gave birth to the first cardioid mics. Yet, microphone evolution did not stop with a cardioid. Now, there are also hypercardioid, omnidirectional, and wide cardioid mics. Here are the three different types of cardioid mics:
1) Hypercardioid Microphones
The hypercardioid microphones exhibit less sensitivity to sound from the sides, including those above and below. Compared to the ordinary cardioid mics, of course, they are less sensitive to these sounds. Yet, they don’t get totally null the signals from the sides. They still show some picking up of sound from the sides, below, and above. But they are less sensitive to these sounds. Thus, they are more directional because they are more focused on the sounds from the front.
They reject off-axis sound. Moreover, their null points are at 35° and 45°. They also exhibit minimal sensitivity at 180° behind the microphone.
The hypercardioid mics are the next significant advancement in the development of cardioid patterns. Yet, this development also left a small area of sensitivity at the rear of the mic.
2) Omnidirectional Microphones
These are microphones that pick up sounds from different directions more evenly. A graphic representation of what the omnidirectional mic picks up is like a circle. Yet, despite picking up sound frequencies from all directions, omnidirectional mics also tend to become directional when it comes to high frequencies. Hence, you must direct this mic to the source of the sound to prevent picking up more spill and off-axis echoes and reflections.
The omnidirectional mics, of course, have transparent and more open sound as compared to directional microphones. You can also position this mic closer to the source of sounds without sounding muddy or boomy.
3) Wide Cardioid Microphones
Wide cardioid microphones are less directional as compared to cardioids. Yet, it is more directional than the omnidirectional microphones. They tend to pick up sounds from the front of the mic. They are also sensitive to sounds from the mic’s sides, below, and above. Behind these microphones, however, you can find the null point. Their sound, of course, strikes a balance between the directional control of cardioid mics and the openness of the omnidirectional mics.
How Does Cardioid Cancel the Sound from the Rear?
Before we discuss how cardioid mics work, let’s discuss first the omnidirectional mic. In an omnidirectional mic, the sound reaches the diaphragm of the transducer. Then, it creates signals. However, the sounds from the mic’s side and rear bend around to reach the front of the mic. This sound also presses on the diaphragm’s front and creates signals. Hence, in an omnidirectional mic, the mic responds to all the sounds from all directions. In other words, the omnidirectional mic exhibits an omnidirectional polar pattern. Yet, omnidirectional mics also become directional relative to high frequencies.
When it comes to cardioid mics, the sound waves also follow the same path. Yet, the sound that enters the rear part of the diaphragm and the sounds that enter the sides are delayed. This is because of its specialized acoustic phase-shift network. In this way, the sounds from the rear are canceled.
This cancellation of sound from the rear happens in this way. When a sound wave from the back comes near the mic, it moves to the diaphragm via two paths. It travels inside and outside the mic via the ports. Some of the sound waves also move to the diaphragm’s front and outside the mic. The travel time of the sound from the rear to the front entails a certain amount of time. Some sound waves also enter the rear ports and are delayed. The cardioid mic, however, configures the movement of the sound waves from the rear and front of the diaphragm to arrive at the same time.
Sounds also push on both sides of the diaphragm in phase. The diaphragm can’t move when these sounds from the sides enter, and thus, they make a weak signal. Rear sound is also canceled out as well as the sounds from the sides. Yet, the sounds from the front are not canceled out. The frontal sound, of course, also travels to the rear ports. But there is a further delay in the movement of the sound. Thus, it doesn’t cancel out the front sound. The frontal sound, therefore, is the one that creates the strongest signal.
When to Use Cardioid Mics?
If you intend to mike a single source of sounds, the cardioid mic is a perfect choice. You can also use it when spot-miking individual instruments in an ensemble. You can also use this mic when miking individual percussions. Moreover, the cardioid mic is perfect for capturing a single vocal in the studio. You can also use it for close-miking instruments within the studio.
Another thing is you can use the cardioid to reinforce sounds. You can also use it if you need high gain before feedback. Plus, you can use it if you want to isolate sound in a noisy ambiance.
It enables you to capture audio signals in a less ideal environment. You can also use it if you want an in-your-face recording. Lastly, you can use it for maximum rejection of rear sound.
When Not To Use Cardioid Mics?
Some situations do not necessitate the use of cardioid mics. It is not advisable to use it, for example, when there is off-axis coloration. Moreover, it is not suitable to use when the singer has plosive issues. You should also not use it if you don’t need an in-your-face effect. Lastly, you don’t have to use it if you want a natural room recording.
The use of the cardioid microphone comes with many advantages. It is also a popular choice among audio engineers. It is the type of mic that offers a high percentage of applications. Hence, you will appreciate the different applications afforded by cardioid mics. So, if ever you are confused as to whether to use cardioid mic or not, just go back to the abovementioned applications of cardioid mics. Then, you can make an informed decision on whether to use a cardioid mic or not.