Whenever a new headset is announced, one of the aspects highlighted in the data sheet is the type of driver used by the manufacturer. Unlike computer software, which works as a kind of “dictionary” to allow communication between parts of the PC, headphone drivers are the mechanism inside the shells or capsules (in the case of TWS headphones) responsible for generating the sound you hear when you watch a video or listen to music.
To better understand how it works, you need to remember some physics concepts, more specifically waves — disturbances in space that transport energy, by the most basic definition. There are two types of them: electromagnetic, like light, which don’t need a physical medium to travel; and mechanics, like sound, which need an object to be able to spread. That’s why, for example, you can hear your own voice when talking with your ears covered, as the sound is traveling through your head to them.
With that out of the way, we move on to the drivers. These structures work like the inverse of the ear, transforming an electrical signal sent by your cell phone, headset or other device into a sound wave when it begins to vibrate. Vibrations use the air as a medium to spread and then reach your ears. That said, there are a variety of driver types, each with its pros and cons.
dynamic driver
The most popular model, the dynamic driver is the choice of most audio devices on the market because they have a lower production cost than other types. Essentially, this model uses a magnet (usually neodymium), a copper coil and a membrane or diaphragm — as it receives information from the music, the magnet changes its polarity, forcing the copper coil to move closer or further away. Attached to the diaphragm, the coil makes it vibrate as it moves, thus generating sound.
In addition to the low cost, the dynamic driver has the strengths of requiring less energy to operate, eliminating the need to use an amplifier and allowing even simpler devices (such as smartphones) to be able to operate them, in addition to having more area to operate. , generating more air pressure and facilitating the production of bass frequencies (which does not necessarily mean better quality).
Among the weak points, we have a greater chance of audio distortions, especially at higher volumes, and a greater chance of delivering a frequency response (basically the frequency range in which the driver can vibrate, generating bass, medium and treble) less wide. The dynamic driver is considered to be the least accurate of all types due to these limitations, but it can be tweaked to deliver quality audio, as evidenced by the existence of some high-fidelity Hi-Fi certified headphones that use it.
pros
- Low production cost
- thicker bass
- Lower energy requirement to function
Contras
- More susceptible to distortion
- less precision
- Less likely to deliver a wide frequency response
magnetic planar driver
Often found on headphones aimed at audio enthusiasts, the magnetic planar driver already falls into a premium category and is considered a high-precision model for the way it works. The concept is similar to that of dynamic drivers, moving a diaphragm through magnets to generate sound, but its organization and components are quite different.
In a configuration similar to a “sandwich”, two large magnets embrace the diaphragm — extremely thin over here —, which houses an electrical conductor inside. As the polarities of the magnets vary, the electrical conductor moves and makes the membrane vibrate, generating audio. With this structure, its appearance is quite peculiar, as it looks like a large flat rectangle (hence its name).
Also known as isodynamic or orthodynamic, the magnetic planar driver is recognized for the high precision it delivers, as it moves uniformly throughout its length, in addition to the wide frequency response and the absence of distortion, even at the highest volumes, which is why it’s common to find it on reference headphones, aimed at audio professionals and enthusiasts. Still, it’s not perfect: because it uses larger magnets, this type is much heavier than the dynamic driver, and its construction makes it much more expensive.
In addition, it requires much more energy to operate, making a significant number of devices that adopt it require an amplifier — there are some headphones, including those intended for gamers, that already reduce this limitation by implementing batteries in the body, slightly expanding the list. devices that can use them.
pros
- High precision
- Ease of obtaining wide frequency response
- No distortion even at higher volumes
Contras
- High manufacturing cost
- Increased weight due to the use of larger magnets
- Requires more power and often an amplifier
electrostatic driver
Regarded as the most accurate driver that delivers the best audio quality, the electrostatic driver works in a completely different way from other types by taking advantage of static electricity. No magnets here—the diaphragm is an ultrathin membrane that floats between two metal plates, subjected to electricity to generate the static needed to move the diaphragm. Because it is not fixed in any one spot, and moves uniformly, the membrane is distortion-free and provides an extreme frequency response.
Extremely expensive to manufacture, the electrostatic driver is used only in the most premium models of headphones — such as the Sennheiser HE 1, the most expensive headphone in the world, sold to order for US$ 65 thousand (more than R$ 300 thousand). This model also requires a huge amount of energy to function, so the use of an amplifier is mandatory, and it is necessary to adjust it for each phone, characteristics that make its production in large quantities impracticable.
pros
- Considered the most accurate driver
- Membrane is not fixed, ensuring zero distortion
- extreme frequency response
Contras
- High manufacturing cost
- Requires custom amplifier for each headphone
- Mass manufacturing is not feasible
balanced armature driver
Mainly used in in-ear headphones (those with small capsules, which fit inside the ear) and hearing aids, the balanced armature driver stands out for its compact size and low power requirement. Its operation is similar to that of the dynamic driver, but a more ingenious structure is used: a metal armature is positioned in a balanced way between the positive and negative poles of a magnet (the reason behind the name), and wound on a copper coil, while the diaphragm is fixed at its tip.
When activated, an electric current passes through the coil and, as this happens, the armature begins to vibrate as it is trying to rebalance itself between the poles of the magnet. This movement is transferred to the diaphragm, which vibrates and thus generates sound. The focus of the balanced armature driver is on portability, which is why we often see it in smaller headphones like TWS models, although dynamic drivers are also heavily used in this segment.
Due to its characteristics, this model has some limitations of its own: the bass is not so marked, and the frequency response is quite limited compared to other types, which motivates companies to use more than one balanced armature driver, with each one intended for a range of frequency response. It is also not uncommon to see a combination of them with the dynamic driver, which would be responsible for the bass, its strong point.
pros
- light and compact
- Requires less energy to run
- It has a good frequency response in the high range.
Contras
- Bass frequencies don’t have as much presence
- Operate in smaller frequency ranges than other types
- More expensive to produce than dynamic drivers
magnetostriction driver
The last most popular type of driver is also the most curious: the magnetostriction driver. Despite the complicated name, this model is not from another world: it is the type used in bone conduction headphones, which transmit sound through vibrations in the user’s skull. Its name also indicates the way it works — the component takes advantage of the phenomenon of magnetostriction, which is basically the change in shape of a ferromagnetic body when under the influence of a magnet, generating vibrations.
These vibrations travel through the user’s bones, then reach the ears. The operation has another curious effect: the possibility of using them underwater, since the air is not involved in the sound journey. As they do not block the ear canal, headphones with magnetostriction drivers are recommended for outdoor activities. On the downside, there isn’t any isolation, the sound quality is lower than other types of drivers, and there’s more sound leakage, even if it’s not as audible.
pros
- Does not block the ear canal, allowing the wearer to hear sounds around them
- Usage is possible even under special conditions such as underwater
Contras
- Low sound quality
- there is no isolation
Other important aspects of headphones
It’s important to note that the audio quality of a headset doesn’t just depend on the type of driver — there are a number of aspects that influence audio quality, listed below.
- driver size: Measured in millimeters (mm), it represents the diameter of the driver. The general rule of thumb is that bigger is better, as a larger driver generates more pressure and moves more air, ensuring louder volume and more powerful frequencies. That said, it is also necessary to remember that size is not the definitive rule, and there are several other aspects that must be considered when buying.
- Number of Drivers: as we mentioned, there are headphones that use more than one driver, either to ensure a wider frequency response or to compensate for some limitation (as in the case of armature drivers). Quantity does not guarantee better quality, but it is good to observe the configuration adopted by the manufacturer.
- Frequency response: Measured in Hertz (Hz), the frequency response represents the range of vibrations that the headset can reproduce. To understand better, you need to remember that human hearing is capable of hearing sounds between 20 Hz and 20,000 Hz (or 20 kHz), and almost all modern headphones are capable of delivering this frequency response. However, having a wider response (like anything between 8 Hz and 40 kHz) ensures a greater level of sonic detail. Headphones that deliver wider ranges like this are considered high definition, or high fidelity (Hi-Fi).
- Impedance: Measured in Ohms (Ω), it basically represents the difficulty that the energy sent to the driver will face to move it. The higher the impedance, the more power is required, and therefore the more difficult it is for the connected device to use the headset in question. Dynamic and balanced armature drivers usually reach 38 Ohms, while the more difficult electrostatic ones can reach an incredible 600 Ohms in the most advanced models.
- Codecs: In addition to the technical aspects of sound, Bluetooth headphones in particular also have connectivity specifications that affect audio quality, including codecs. Basically, codecs are algorithms used by manufacturers to compress and send information over the wireless connection without having major problems due to the limitations of the amount of data per second that this method of communication has. The most common are SBC and AAC, but there are others dedicated to those looking for better audio quality, such as aptX Lossless and LDAC.
