The difference between dynamic and balanced iron units

1. Structural characteristics of dynamic armature earphones

First of all, we need to understand the differences between the structural principles of moving iron and moving coil. In terms of the sound-generating process, moving iron earplugs and moving coil are basically similar, both rely on the vibration of the voice coil in a permanent magnetic field to generate sound. The biggest difference is that the structural principle and position of the sound unit are different.

Inside the moving iron earplug, the voice coil is wound around a precision iron sheet called the "balanced armature" located in the center of the permanent magnetic field. This iron sheet drives the diaphragm to produce sound under the action of magnetic force. The moving coil directly drives the diaphragm, while the moving iron transmits the power to the center point of a micro-diaphragm through a precisely structured connecting rod, thereby generating vibration and producing sound.

In terms of the unit position, traditional dynamic earplugs cannot put the entire sound unit into the ear, while the dynamic iron type can be easily put into the ear canal because the unit is much smaller. This approach effectively reduces the area of ​​the in-ear part and can be put into a deeper part of the ear canal. Since the geometric structure of the ear canal is much simpler than the auricle and is quasi-circular, a soft silicone cover can provide good sound insulation and sound leakage prevention effects compared to traditional earplugs.

The above is what I have summarized from the limited information I can find at the moment. Some articles on the Internet that introduce balanced armatures are full of errors, so I hope you will pay attention. In fact, the structural principle of balanced armatures is not very complicated, but the manufacturing cost and technology required are much higher than dynamic coils. Why are most high-end earbuds balanced armatures? This requires talking about the advantages of balanced armatures.

2. What are the advantages of dynamic armature?

The sound insulation effect of the moving armature is better than that of the dynamic in-ear headphones. Since the dynamic unit has a larger area and requires more space and air to vibrate during the sound production process, it cannot effectively control the sound leakage phenomenon; the moving armature can effectively reduce the area of ​​the in-ear part and can be placed deeper in the ear canal. (Almost all dynamic earphones have air holes, while air holes are rarely seen on moving armature earphones. CK9 is an exception.) Since the geometric structure of the ear canal is quasi-circular and much simpler than the auricle, a soft silicone cover can provide good sound insulation and sound leakage prevention effects compared to traditional earplugs.

The sensitivity of the moving iron is higher than that of the dynamic coil. The main reason is that the structure of the moving iron unit is almost a closed container structure. A small amount of current can drive it. Here we should pay attention to the relationship between sensitivity and resistance. It is precisely because of the higher sensitivity that the moving iron earphone has better transient performance, and the dynamic performance of music, instantaneous detail performance, and sound density are far better than the dynamic coil earphone.

The frequency response curve of the balanced armature earphone is more stable. The frequency response curve of the dynamic coil earphone will show some audible changes in different temperatures, humidity and during use. The balanced armature shows good stability, making the sound quality more stable and reliable, and not easy to change. A very important reason is that the balanced armature unit is almost always made of metal materials and formed by high-precision molds, while the vibration diaphragm of the dynamic coil unit is generally combined with the coil by glue, so there are many influencing elements and individual differences. Therefore, the electroacoustic performance of the dynamic coil unit is much more stable.

The balanced armature is smaller and lighter. This is due to the characteristics of the balanced armature unit. The weight of the balanced armature diaphragm increases linearly with the increase of the unit diameter. Therefore, balanced armatures are more suitable for in-ear earplugs with smaller volumes. It is impossible to make them into open or semi-open earplugs. This is also the reason why balanced armature technology is currently only used in in-ear earplugs.

Balanced iron earphones help protect hearing. As mentioned earlier, balanced iron earphones generally have good sound insulation, and their extremely high sensitivity allows for good performance even at very low volumes, so you can enjoy pure sound without increasing the volume in a noisy environment. Balanced iron units are widely used in medical, health care, aviation, military and other fields, and hearing aids are more common. Doctors will not recommend products that may harm health to patients, and basically all well-known hearing aid brands use balanced iron units, so balanced iron earphones are safer to use than dynamic coil earphones.

3. What determines the sound quality of dynamic armature earphones?

The sound quality of earphones is a commonplace issue.
As we all know, the sound quality of dynamic earphones mainly depends on the material of the diaphragm and the material and structure of the cavity in terms of hardware, while the magnet mainly determines the driving performance of the earphones. Among them, the design of the cavity plays a vital role in the sound performance of dynamic earphones. From the above, everyone has a general understanding of the basic structure of the moving iron. The parts that determine the sound quality of the moving iron earphones are obviously different from those of the moving coil.

First of all, the cavity of the moving iron earphone has little effect on the sound quality. This is a significant feature of the moving iron. The main function of the cavity of the moving iron is to fix the stability of the moving iron unit and the outlet, and there is no strict and fixed requirement. This is why even a meticulous manufacturer like Audio-Technica was not particular about the treatment of the shell when producing CK9. Only the front guide port requires a high degree of sealing because it needs to fix the unit and filling materials, and the requirements for the mold are also quite demanding. Some players, even some veterans, often talk seriously about the cavity of a certain moving iron earplug, so the sound is like this and that. Basically, it can be determined from a theoretical level that all these remarks are fabricated. In fact, as long as the cavity can achieve good sealing, it will not affect the sound performance.

So, what affects the sound quality of balanced armature earphones? On the one hand, it is the balanced armature unit, which is obvious. Compared with the dynamic coil, the balanced armature unit has a more sophisticated internal structure and a higher production cost (it should be noted that this is not the main reason why balanced armature earphones are generally expensive). It is the basis of the sound quality of the earphones, and the advantages of balanced armature over other earphones are mainly reflected in it. A good earphone must use an excellent unit.

In fact, there is another more important aspect of the sound quality of the balanced armature. As we all know, the sound quality of the ER4P, which also uses a single unit, is much higher than that of the UM1. Of course, the unit accounts for part of the reason, but on the other hand, it depends more on the sealing ring, the component that contacts and connects the unit and the shell inside the balanced armature earplug cavity. This sealing ring reflects more than half of the technical level of balanced armature earphone manufacturers. The difficulty of balanced armature earphones lies not only in the unit, but also in this small sealing ring. The function of this rubber ring is to further enhance the sealing of the unit and to modify the sound conduction. Different tuning materials and different process technologies will result in different sound performances. Compared with dynamic coils, the tuning of balanced armatures basically depends on the adjustment of the material and structure of the sealing ring. Its adjustment level requires extremely precise technical level, which mainly determines the difficulty of producing balanced armature earphones. Therefore, balanced armatures cannot be produced by only units, and it is not the kind of small copycat factory that can assemble them at will like dynamic coils to make good sound.

The technologies mentioned above are core business secrets, so Shure, UE, and Etymotic never reveal more technical details to the outside world. This is one of the reasons why people generally know very little about balanced armatures. It should be noted that the above analysis is only from the perspective of hardware and structure. Just like dynamic coils, there are many factors that affect balanced armature headphones, which are difficult to list here one by one.

4. Do I need to praise the dynamic armature earphones? How to praise them?

First of all, it should be said that the balanced armature earphones, like the dynamic coil earphones, also need a process of aging before they can enter a stable state. "Aging" has nothing to do with the dynamic coil and balanced armature earphones. Its significance lies in the mechanical running-in of the earphones to reach a relatively mature and stable state.

What I want to say is that compared with dynamic coil earphones, the sound of dynamic iron earphones may change greatly before and after stimulation. The sound may be more natural and smoother, the connection between the three frequencies may be smoother, and the low-frequency dive may be increased. However, the change is mainly in quantity. Due to the special structure of the dynamic iron unit, the style orientation of the sound is basically determined, and it is basically impossible to have a huge change like EX01.

So how should the balanced armature be driven? There is no clear conclusion in this regard so far. Here are some methods of experts. The basic argument is still the ordinary natural drive, that is, use the general sound source to drive, that is, use the general sound source to play various music slowly. Of course, it is not ruled out to use radio white noise and ordinary pink noise. Many players suggest not to use signal scanning to drive the balanced armature, and the reason needs to be verified. Generally speaking, the balanced armature will enter a stable state faster.

5. Difficulty in driving dynamic iron earphones

Dynamic iron earplugs can be roughly divided into the following three categories according to the difficulty of driving:

1) I think the "low impedance + single unit" dynamic iron earphones are the easiest to drive. As long as you have a portable player like IPOD4, you can use 70% to 80% of it. The examples above also belong to this category. (Representatives: E4C, UM1, ER4P)

2) High-impedance single-unit dynamic iron earphones are not easy to drive; and they are picky about the headphone amplifier. This type of earphone is obviously not suitable for direct driving with a walkman. It needs to be used with a headphone amplifier with high swing. (Representative: ER4S)

3) It is generally believed that dual-unit or even triple-unit dynamic iron earphones are more difficult to drive than single-unit earphones. (General opinion, the reason needs to be verified)

Another point is how to drive it well. Due to the high sensitivity of the dynamic iron earphone, the dynamic iron earphone has very high requirements for audio signals. Generally speaking, only very high-end flash memory devices (such as U3) and hard disk MP3s with sufficient thrust are worthy of dynamic iron earphones. If you use a T29 or M6 that you think is high-end with a dynamic iron earphone, it will be a joke of a small horse pulling a big cart.