1 Start: What is directivity?
The directivity of a microphone means that the microphone picks up sound from different directions. In the field setting, the most important thing is to confirm the type of microphone you are using, so as to reduce the feedback of the sound and where is the best place to place the monitor according to the use of directivity. In the studio, you can use sensors with different characteristics to make changes. It's like arranging certain decorations during recording, or proximity effect.
Directional microphone: Classified according to the form of polarity, it is much more sensitive to the sound from the front than the sound from the back. The directional microphone has two openings at both ends of the diaphragm, one on each side. The vibration of the diaphragm depends on the phase relationship and the pressure difference between the two ends. A fine acoustic filter is placed at the front end of the rear sound hole to act as a time delay, so that the sound from the rear can reach the diaphragm from the front and rear sound holes at the same time and cancel it out, so the polar pattern of the directional microphone is in the shape of a heart. .
Term explanation: proximity effect
Each directional microphone (cardioid, super cardioid) has the so-called proximity effect. When the microphone is close to the sound source, the bass frequency response increases, so the sound is fuller, thereby producing the proximity effect. Professional singers often use this effect. If you want to test the effect, try to gradually bring the microphone closer to your lips while singing, and then listen to the changes in the sound.
2. Cardioid: Only pick up the direction facing the microphone
This is the type of microphone most often encountered by singers. It is often described as having a heart-shaped pattern, and is usually used in studio recording of vocals. When you don’t want to pick up the audience’s voice or the sound from your monitor, the cardioid microphone is very suitable in this case (when using a cardioid microphone, the monitor should be placed opposite you, 180 degrees from you. ). In the studio, the use of cardioid microphones can effectively reduce the surround sound and the sound reflected by the microphone. This can help you record in undesirable environments, or reduce the sound of other music around you.
This kind of direction is named after its pickup range is like a heart: in front of the microphone, its sensitivity to audio signals is very high; when it goes to the side of the microphone (at 90 degrees), its sensitivity is also good, but It is 6 decibels lower than the front; finally, it has a very good shielding effect for the sound from behind the microphone. It is precisely because of this shielding effect on the sound behind the microphone that the cardioid pointing microphone is very useful in multiple recording environments, especially when a large amount of indoor ambient sound needs to be eliminated. In addition, this microphone can also be used for live performances, because its shielding function can cut off the echo and environmental noise generated during the performance. In practice, cardioid microphones are also one of the most frequently used microphones, but remember that like all non-omnidirectional microphones, cardioid microphones will also show a very obvious proximity effect.
3. Super cardioid microphone
This kind of directional microphone is more and more popular in the scene, such as Shure Beta 58 or TC-Helicon MP75, they can better record the voice of the lead singer and block the sound of the surrounding bands on the stage. The disadvantage is that some sounds behind the microphone are also recorded. This means that you should not put your monitor speakers in front of you (in general, a position of 120 or 240 degrees is better) or you will hear echoes. Supercardioid microphones are usually used in studios. When you need to isolate other sounds to a greater extent, they are rarely used to record human voices.
This type of pointing is very similar to over-cardioid, and is often confused. However, the directivity of general over-cardioid is slightly worse than that of over-cardioid, and its sensitivity to the sound from the back of the microphone is also smaller. Much.
Its directivity is stronger than that of the heart shape, and it has a "tail" on the back
The directivity of the super cardioid microphone is narrower than that of the cardioid, which is particularly suitable for close-range pickup. It is particularly special for fixed-point recording of drums and pianos. Its directional characteristics are very suitable for on-site recordings that require isolation (sometimes to isolate interference between instruments, and sometimes to isolate noise). For self-playing and self-singing performance recordings, the mutual crosstalk of super-directed microphones is small
4 Omnidirectional: Collect all the sounds around you
The omnidirectional microphone has the same sensitivity for all angles, which means it can pick up sound evenly from all directions. It is rarely used in live recording because of echo. However, it is a very effective tool in the studio, especially if you want to pick up all the sounds in the room. Another feature of the omnidirectional microphone is that it does not change more sound characteristics with distance. In other words, even if the singer moves on the stage, the recorded sound will not change much, and the sound will be natural. You can also often see the use of omnidirectional microphones on these occasions, and all the singers and musicians of traditional folk orchestras gather to perform. The omnidirectional microphone can balance the overall performance in the audience.
This directional microphone, as the name suggests, is equally sensitive to audio signals from all directions around the microphone. The big advantage of this microphone is that it does not produce obvious proximity effects
Omnidirectional microphones have the same sensitivity and frequency response to sounds from all directions. Compared with the cardioid microphone, the sound field picked up by the omnidirectional microphone is wider, which is especially suitable for recording chorus, environmental sound effects, and acoustic instruments, because it has a particularly good sense of space, and it is close to the cardioid microphone. The effect is relatively small, which has the advantage of being insensitive to the slight movement of the sound source. Another feature of omnidirectional is that it does not require much equalization. These early theoretical data, however, when the omnidirectional microphone picks up the sound source of the 360-degree sound source, it is impossible to achieve complete equality. The actual situation is that there must be a little recessed state behind the microphone head, and the frequency response will not be very high. the same. As the diaphragm increases, this point becomes more prominent.
5. Figure 8: usually a ribbon microphone
As the name suggests, the shape of the figure 8 microphone is similar to the number 8. Also called double cardioid microphones or bidirectional microphones, they are usually used in studios rather than on-site, and most of these microphones are ribbons. Microphone. They pick up sound from the front and back, not from the sides. If you use a figure-eight ribbon microphone to record human voices, you need to pay attention to the phase problem caused by room sound reflections to the microphone. Recording performances of two singers is a figure-eight type is a major use of ribbon microphones. You can have one singer in front of the microphone and the other on the other side, which can also reduce the sound reflection in the room.
This is the most sensitive on the front and the back, the left and right sides are the least sensitive, because this directional microphone has the same high sensitivity to the audio signal from the front and back of the microphone, but it is not very sensitive to the signal from the side of the microphone. In this way, the pickup range is shown on the drawing, which looks like a figure eight, and the position of the microphone is exactly at the cut-off point of the figure eight, hence the name.