Multiple units ≠ good sound! After reading this popular science of the principle of unit sound, break the "unit marketing" trick of headphone manufacturers

Multiple units ≠ good sound! After reading this popular science of the principle of unit sound, break the "unit marketing" trick of headphone manufacturers

In recent years, there has been a trend of stacking units in the headphone field. From the previous one dynamic drivers with four balanced armature drivers, eight balanced armature drivers, to more than ten or even twenty units, there is quite a way to invite the entire symphony band into the ear. At the same time, some manufacturers also focus on the number of units in their publicity, first of all, to overwhelm their competitors in terms of quantity; the argument that multiple units equals a good voice among enthusiasts is rampant so that most people can only feel their wallets that are not full.


So, is multi-unit necessarily equal to good sound? In this regard, earphones and love have the same purpose. In most relationships, sending a carload of pears is not as good as sending an apple that someone wants. Of course, it does not rule out that the person you are chasing only likes the quantity and doesn't care about the item. In most cases, the properties of the unit are far more important than the quantity. Therefore, we AIHOOR will bring everyone back to the essence and understand various headphone units in principle to facilitate the search for your favorite sound in the future.


The basic principle of the headphone unit is to convert electrical energy into mechanical energy, but in terms of the specific implementation, several major technical systems with different structures and distinct characteristics have been developed. Some units are capable of acting on their own, single-handedly handling the sound of the full frequency range, while others respond to a narrow frequency band and are good at group operations. In the course of the development of headphones, there have been many interesting units and technologies. After technical and market tests, the units that are still very popular today include the following: dynamic drivers, balanced armature drivers, electrostatic units, and planar magnetic drivers.


Dynamic drivers

Dynamic drivers headphones first appeared in 1937, and the current mainstream view is that Beyerdynamic has produced the world's first pair of dynamic headphones. Most of the earphones on the market now use dynamic drivers. From the $10 wired earphones to the high-end earphones over $200 bucks. Especially open ear headphones and semi-open ear headphones use dynamic drivers. The reason why the dynamic drivers are so popular is that it is a very mature structure. Except for earphone products, most of the units of various speakers also adopt similar designs.

 dynamic drivers

The dynamic drivers are composed of a coil, a diaphragm, a magnet, and other structures. The enameled coil is in a permanent magnetic field, wound into a cylindrical shape, and connected to the diaphragm. The coil is driven by a signal current to drive the diaphragm to vibrate, and the diaphragm vibrates to produce sound.


The core components of the dynamic drivers are the diaphragm and the coil, so the parameters related to this have also become an important reference for the quality of the headset. Such as impedance, sensitivity, response frequency range, and so on. The lighter and stiffer the diaphragm, the higher the quality of sound it often provides.

The advantage of dynamic drivers is that their sound is very loose and natural, the diaphragm size is large, and low-frequency diving is also easy to do well. Maybe the dynamic drivers do not have the high, middle, and low-frequency tri-frequency as accurate and beautiful as the balanced armature drivers' earplugs, and the analysis of human voice is not as good as that of the balanced armature drivers, but the overtones of the high and low-frequency bands brought by the high-end dynamic drivers are beyond the balanced armature drivers. The low frequency and reverberation of the dynamic drivers are the shortcomings of the balanced armature drivers. If you used to listen to the dynamic drivers, you will feel that the soundstage of balanced armature drivers is narrow. It is thick and upright, with a huge sense of atmosphere and envelopment, but it is still the absolute strength of large-unit dynamic headphones.


Balanced armature drivers unit

After talking about the dynamic drivers, let's talk about the balanced armature drivers. In the process of sound production, the balanced armature drivers earplugs and the dynamic drivers are similar, and both rely on the vibration of the coil in the permanent magnetic field to produce sound. The biggest difference between the two is the construction principle and location of the sound unit. Inside the balanced armature driver's earplugs, the voice coil is wound on a precision iron piece called "balanced armature" located in the center of the permanent magnetic field. This iron piece drives the diaphragm to make a sound under the action of magnetic force. The dynamic drivers directly drive the diaphragm, and the balanced armature drivers are transmitted to the center point of a micro-diaphragm through a precisely structured connecting rod, thereby generating vibration and sound.

In terms of sound, there is still a big difference between the balanced armature drivers and the dynamic driver's earplugs. The structure of the balanced armature drivers unit is almost a closed container, and only a small current is needed to drive it, so the sensitivity and resolution have always been the strength of balanced armature drivers. The advantages of balanced armature drivers headphones are excellent in the playback of sound details. However, the balanced armature drivers are limited to the volume and sealed design, and it is still far from the level of open-type dynamic drivers headphones in terms of the sound field. In addition, the "iron feelings" of balanced armature drivers' earphones are also criticized. The sound is mechanical, clean, or not too emotional. To give an inappropriate example, the drum sounds of balanced armature drivers are always "bang bang bang", which makes dynamic drivers are much more real.

The diaphragm of the unit of the dynamic driver's earphone is generally bonded to each other by glue and the guide coil. There are some individual differences in each unit, and it is also affected by the temperature and humidity of the surrounding environment. The balanced armature drivers unit is made of metal materials, manufactured through high-precision molds, and the sealing design of the earplugs makes the frequency response curve and overall sound quality of the balanced armature drivers earphones more stable.


Due to the sound insulation, balanced armature drivers' earphones are more helpful in protecting hearing. And the extremely high sensitivity enables a small volume to have a good performance. The balanced armature drivers unit is widely used in medical, health care, aviation, military, and other fields. The most common of these are various types of hearing aids.


In a nutshell, the balanced armature drivers' voice was sharp, fast, and clean. The dynamic drivers are full, rich, and thick. The balanced armature drivers performed better in listening to the medium and high frequencies; the dynamic drivers is better in listening to the middle and low frequencies.


Dynamic drivers + Balanced armature drivers

Speaking of which, some people may want to ask, is there a way to combine the characteristics and advantages of dynamic drivers and balanced armature drivers? The answer is of course yes. Hybrid headphones have become a hot spot pursued by major HIFI manufacturers. The most representative one is naturally the famous AKG K3003. The combination of K3 balanced armature drivers + dynamic drivers not only ensures the musical atmosphere of the dynamic drivers but also ensures the delicate analysis of the balanced armature drivers. If you don't consider its high price, it can be said to be an ideal solution. However, the connection, phase, and transition of characteristics between different units brought about by multiple units also bring great difficulties to the design and manufacture. You need to pay more attention when purchasing.

Electrostatic unit

Electrostatic earphones are the most unique working principle among all kinds of earphones today. To avoid the disadvantage that the traditional diaphragm is easily distorted due to physical limitations, the electrostatic unit has abandoned the structure of driving the diaphragm with a coil, hoping to find a way to make the entire diaphragm even and complete. The electrostatic earphone uses an external booster to provide a very high voltage (up to nearly 600V), which is connected to the special diaphragm made of vacuum metal evaporation so that the diaphragm is fixed and filled with positive charges, and then the external sound signal, after passing through an inverter, it is input to the fixed electrodes on both sides respectively, and the force of pulling and pushing the diaphragm is generated by the mutual repulsion and attraction between the charges. The advantage of this is that the force on the diaphragm is very averaged, and the distance between the plate and the plate is very close, any tiny signal can be converted into a driving force, so it is very sensitive. In addition, there are more options in the diaphragm material. For example, the polymer diaphragm is not only extremely thin but also extremely light in weight, which greatly improves the performance of the earphone.


Electrostatic headphones must use a special amplifier to convert the audio signal into a voltage signal of hundreds of volts and use a transformer to connect to the output of the power amplifier to drive electrostatic headphones. Therefore, it is expensive and not easy to drive, and the sound pressure level it can reach is not as large as that of dynamic drivers headphones, but it has a fast response speed and can reproduce various tiny details, with extremely low distortion and very high quality.


The following figure is a comparison of the sound principle of dynamic drivers balanced armature drivers and static electricity

Due to their high technical cost, electrostatic earphones are produced by fewer manufacturers. The most important ones for electrostatic earphones are STAX and Gaussian, among which STAX is a typical representative.


STAX is a well-known electrostatic earphone manufacturer in Japan. There are only more than 40 people in this manufacturer, but these 40 people support a miracle in the earphone industry, just like Grado's "small workshop" factory. But STAX is the only manufacturer that specializes in electrostatic earphones. At the end of 2011, 100% of STAX's shares were acquired by Edifier for less than 2 million US dollars and became a sub-brand of Edifier. It is not inferior to European and American companies in the pursuit of the ultimate, and almost all of its products are incredible. STAX's current flagship is the SR-009, and the price is currently around $7000. Different from traditional dynamic headphones, electrostatic headphones require a special headphone amplifier to match, and it is impossible to have only one headphone to make it sound. However, the price of amps is not cheap, so they often said "static headphones are the toy of the rich".


Planar magnetic drivers

The internal structure of the planar magnetic drivers is similar to that of the electrostatic earphone, and a large-area flat diaphragm is used, which is suspended in two sets of magnetic poles opposite to permanent magnets. The difference from the operating principle of the electrostatic drive unit is that the planar magnetic driver prints the circuit on the diaphragm, and the diaphragm is driven by the magnetic field. The working principle is closer to the dynamic drivers than the static electricity.


The circuit of the planar magnetic drivers is generally evenly distributed on the diaphragm, which makes the flat diaphragm, like the diaphragm of an electrostatic earphone, uniformly stressed in a consistent magnetic field, which makes the flat earphone less disturbed by split vibration. And thanks to the larger area of ​​the diaphragm, flat-panel headphones can often provide better bass like a dynamic driver.


However, the magnet array used in flat-panel earphones has not been able to reduce the overall weight until the introduction of single-sided magnetic pole technology, but it is still heavier than most dynamic and electrostatic earphones of the same volume. In addition, there is the issue of the thickness of the diaphragm. Since the plane circuit of the earphone is directly printed on the surface of the diaphragm, the thickness and weight of the diaphragm are often not as thin and light as other earphones, which makes the high-frequency response of the diaphragm poor.

Fortunately, with the improvement of technology in recent years, the above problems have been significantly improved, and planar magnetic drivers headphones have attracted more and more attention from manufacturers and music lovers. Now brands such as HIFIMAN and Audez'e are producing planar magnetic drivers headphones, and Ausounds, which firstly produced planar magnetic drivers earbuds, and made the smallest planar magnetic drivers headphones in the world.

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