The principles and advantages of condenser microphones

The principle of condenser microphone

Condenser microphones use the change in capacitance to convert sound signals into electrical signals. This type of microphone is the most common, and the built-in microphone of common recorders is this type. Because it is cheap, small in size, and the effect is not bad. Sometimes it is also called a microphone head.

A condenser microphone has two metal plates, one of which is coated with an electret film (mostly polyperfluoroethylene propylene) and grounded, and the other plate is connected to the gate of a field effect transistor. A diode is connected between the gate and the source. When the electret diaphragm itself carries an electric charge, the surface charge is Q, and the capacitance between the plates is C, then a voltage U=Q/C is generated on the pole. When it is vibrated or rubbed by airflow, the distance between the two plates changes due to vibration, that is, the capacitance C changes, while the charge Q remains unchanged, which will cause a change in voltage. The magnitude of the voltage change reflects the strength of the external sound pressure, and the frequency of this voltage change reflects the frequency of the external sound. This is the working principle of the electret microphone.

Advantages of condenser microphones

Can directly convert sound into electrical energy signals

Capacitor microphones use the principle of capacitor charging and discharging between conductors, with ultra-thin metal or gold-plated plastic film as the vibration membrane to sense sound pressure, so as to change the static voltage between conductors and directly convert it into an electrical energy signal, and obtain practical output impedance and sensitivity through electronic circuit coupling.

The characteristics of original sound reproduction can be displayed

Audio experts pursue "original sound reproduction" as the highest realm of audio! From the analysis of the basic design principles of microphones, it is not difficult to find that condenser microphones not only rely on precise mechanism manufacturing technology, but also combine complex electronic circuits to directly convert sound into electrical energy signals. They inherently have extremely superior characteristics, so they are the best choice for those who pursue "original sound reproduction".

Has an extremely wide frequency response

The diaphragm is the main component of the microphone that senses sound and converts it into electrical energy signals. The material and structural design of the diaphragm determine the various characteristics of the microphone's sound quality. Since the diaphragm of a condenser microphone can be made of extremely light and thin materials, and the induced sound pressure is directly converted into an audio signal, the frequency response bass can extend to ultra-low frequencies below 10Hz, and the treble can easily reach ultrasonic waves of tens of kHz, showing a very wide frequency response characteristic!

With ultra-high sensitivity

Because there is no voice coil load on the diaphragm, an extremely light and thin design can be used. Therefore, not only does it have an extremely superior frequency response, but it also has excellent sensitivity. It can sense extremely weak sound waves and output the clearest, delicate and accurate original sound!

Fast transient response characteristics

In addition to determining the frequency response and sensitivity of the microphone, the ability of the diaphragm to react to sound waves, the so-called "transient response" characteristic, is one of the most important factors affecting the timbre of the microphone. The speed of the microphone's transient response characteristics is determined by the weight of the entire diaphragm. The lighter the diaphragm, the faster the response speed. The extremely thin diaphragm of the condenser sound head has an extremely fast transient response characteristic, which can show a clear, bright and powerful tone and accurate sound and image. In particular, the mid- and bass are completely free of sound coloration and "box sound", and the treble is delicate and crisp, which is the most significant timbre characteristic of the condenser. It can be clearly seen from the following figure that the transient response characteristics of the condenser sound head are far superior to those of the dynamic type.

Features ultra-low touch noise

When using a handheld microphone, the touch noise caused by the contact with the palm of the hand makes the original sound mixed with additional noise, which has a huge impact on the sound quality, especially for wireless microphones with preamplifier circuits. Therefore, touch noise has become an important item in judging the quality of microphones. From the perspective of physical phenomena, when a goose feather and a copper plate fall to the floor, the goose feather can hardly hear the sound of falling, while the copper plate is very loud, which shows that lighter materials have less impact sound than heavier materials. Similarly, the vibration membrane of a condenser microphone is relatively light, and it is inherently characterized by "ultra-low touch noise".

It is drop-resistant and impact-resistant

When using a microphone, it is inevitable that it may malfunction or malfunction due to accidental dropping or collision. Since the condenser microphone head is made of lighter plastic parts and a sturdy light metal shell, the impact force when it falls to the ground is smaller, and the failure rate of damage is lower.

Small size and light weight

Condenser microphones use ultra-thin vibration membranes, which have the characteristics of small size, light weight, high sensitivity and excellent frequency response. Therefore, they can be designed into ultra-small microphones (commonly known as small bees and small ants) for a wide range of applications.

Best suited for wireless microphones

Condenser microphones have the above-mentioned excellent characteristics and have become the favorite of sound engineering experts and singing masters. Using wireless microphones for singing on stage or singing karaoke at home has become a trend in today's world. Wireless microphones can provide the bias voltage required by condenser sound heads and have all the advantages of condenser microphones. They have become the best microphone that professional audio experts dream of in the digital audio era.

Disadvantages of Condenser Microphones

The structure is complex and the cost is high. The sound membrane is fragile and afraid of moisture. Expensive models are stored in vacuum moisture-proof boxes, making them difficult to promote.