The aluminum ribbon microphone is actually a replica of the physical electromagnetic induction phenomenon in junior high school. Its pickup part is an annealed aluminum ribbon about 10cm long, 3mm wide, and 2-5um thick. This aluminum ribbon is placed In a strong magnetic field. When the sound makes the aluminum tape vibrate, the aluminum tape cuts the magnetic induction line to generate a weak current, which is converted into sound after being amplified by the pre-processing amplifier circuit (usually a transformer).
Because the aluminum strip is annealed, the internal stress basically disappears. Therefore, the ribbon microphone has a good frequency response and a great dynamic range. However, the aluminum tape is only a few um thick, so it is more troublesome to use and store than ordinary dynamic and condenser microphones. Blowing during use may cause the aluminum strip to break.
The production process of ribbon microphones is complicated, so the price is expensive. But in professional recording studios you will also see ribbon microphones. The ribbon microphone has a good figure-8 directivity, that is, it can pick up the sound directly in front of and behind the microphone, so it is suitable for recording in chorus and other occasions. In the early years, it was strictly forbidden to use phantom power for ribbon microphones, because doing so would damage the diaphragm. However, the pre-amplification circuit of the current ribbon microphone allows the use of phantom power as the power supply for the pre-amplification circuit. For safety reasons, please be sure to read the manual before using the ribbon microphone.
The ribbon microphone is an ancient professional microphone. It has a figure-eight-shaped sound pickup characteristic map, which can pick up signals from the front and back. The sound is gentle and pleasant, the frequency response is flat, the phase and transient distortion are small, and it can pick up dynamic extremes. Loud sound without distortion. It was widely used in radio stations, recording studios and other professional occasions in the 3rd and 40th to record immortal music for famous musicians and singers of that era. However, the ribbon microphone has a small output signal and is afraid of wind. The shortcomings of belts are susceptible to damp damage, which limits its scope of use. With the emergence of dynamic and condenser microphones with better performance and greater adaptability to the environment, aluminum belt microphones are put into warehouses and gradually forgotten. Until recently, under the wind of nostalgia, some sound engineers used this ancient microphone to pursue the unique sound with strong analog flavor.
The history of the aluminum ribbon microphone is legendary, but its working principle is very simple: a section of aluminum foil acts as a conductor and resonates with sound waves in a uniform magnetic field to generate vibration displacement. When the magnetic field lines are cut during the movement, the two ends of the aluminum foil induce the same frequency as the sound waves. This is almost a direct reproduction of the right-hand rule experiment in middle school textbooks, except that aluminum foil is used instead of the hanging copper rod, and the aluminum foil is usually a narrow strip, which is in the shape of a ribbon, so it is called " Ribbon microphone". In actual aluminum ribbon microphones, since the impedance of the aluminum foil is as low as 1 ohm, a transformer is needed to convert the impedance to a few hundred ohms to match the amplifier circuit behind.
Type of microphone
Microphone, also known as microphone, is a device that converts sound wave vibrations into corresponding electrical signals. When sound waves act on the microphone, an electrical signal output is generated through the energy conversion of the microphone. At present, the commonly used microphones are divided into two categories: electric type and condenser type. Electrodynamic microphones are made of vibrating conductors based on the principle that a conductor vibrated by sound waves generates an induced electric potential in a magnetic field. There are two types: moving coil and aluminum ribbon. The dynamic microphone has better sensitivity and frequency characteristics, simple structure, sturdy and durable, easy to use, and cheap. It is the most versatile microphone. Its frequency range is generally 50～10000 Hz, and high-quality ones can reach 40～16000 Hz. It has high output impedance and low output impedance. The ribbon microphone is a differential pressure microphone with a figure-of-eight directivity. The front and back of the microphone have the same sensitivity, with opposite blind spots on both sides. It has low sensitivity and low impedance. Therefore, this microphone is equipped with an impedance matching transformer. Its frequency response is wide, up to 30 to 18000 Hz. Therefore, it has low noise and low nonlinear distortion, but it is afraid of wind, vibration, and fear. Therefore, it is not suitable for outdoor use. Condenser microphones, also called electrostatic microphones, work according to the principle of changing the capacitance caused by the vibrating plate into electrical signals. It has good frequency response characteristics, high sensitivity, low distortion, large signal-to-noise ratio, small size and sensitivity, etc. advantage. The disadvantage is that the diaphragm is prone to mildew and requires a large polarization voltage, which consumes about 5 to 6 mA. Therefore, the use is subject to certain restrictions .
Use of microphone
Cassette recorders are equipped with one (mono) or two (stereo) electret condenser microphones. The method of using the built-in microphone to record is very simple. As long as a person speaks into the built-in microphone in a normal voice and presses the record and playback keys at the same time, the sound will be recorded. When recording, pay special attention to the distance between the sound source and the microphone. If recording a single person's speech, the distance can be 0.3 to 0.5 meters, and recording singing or musical instrument performance, the distance should not exceed 0.8 meters. If you use an external microphone for recording, you should choose a microphone reasonably according to the content of the recorded program, the scale of the program, the range of activities of the recording teacher, the recording environment, the pros and cons of the tape recorder used, and the input impedance and level. There are three types of microphones: unidirectional, non-directional and bidirectional, and their frequency ranges are different. For recording music programs, a microphone with a wider frequency range should be used. When recording in a noisy environment, a unidirectional microphone should be used. However, it is not appropriate to use ribbon microphones for recording audio textbooks or Chinese opera textbooks. If only one microphone can be used when recording two or more people's speeches, a bidirectional microphone should be used. If you are speaking with multiple people, you should use an omnidirectional microphone and place the microphone in a moderate position. When recording general language, the microphone should be about 0.5 meters away from the sound source. Place the microphone and the sound source on the same horizontal line to avoid loss of high frequencies