(Note : This guide is purely based on my personal experience with the below-mentioned earphone drivers. Of course, I have heard drivers that do not perform like how they are supposed to sound based on this guide but it's rather uncommon. I also understand that different brands of BA/Dynamic/Estat drivers can have a slightly different sound but as I am not well-versed in that segment and this guide is meant to be understood by the general consumer, I would not go into the specifics of it)
In every earphone, there is a driver (or multiple drivers) that produces music to the user's ears, but did you know that not all earphones use the same kind of drivers for their earphones? This guide would expose you to the different kinds of drivers earphones use these days and the kind of sound it provides. I feel that it is important to at least briefly understand the sound characteristic of such drivers so as to know what to expect when looking for an earphone.
This driver is the one most commonly used. From headphones to speakers to earphones, it is being used in almost anything. The dynamic driver works by using a magnet to "push and pull" the voice coil which then produces sound. Due to it being able to displace a large volume of air, it is usually used in producing bass, which requires air to be displaced for it to be perceived. Thus, some companies would state the diameter of the dynamic driver used (10 mm, 13 mm etc)
Dynamic Driver : Consisting of a magnet (1), coil (2), suspension (3) and diaphragm (4)
(Image taken from Wikipedia)
From personal experience, I noticed that dynamic drivers are usually "slower". For instance, when playing songs with many instruments or fast-paced music, it seems to be struggling with producing all the instruments and you might hear less of a particular instrument or that the music sounds "cluttered".
Sound characteristic :
- More focused on mids and bass
- Usually provides deep, rumbling bass
- Slow; does not respond very well to music with many instruments or fast-paced music
Balanced Armature (BA) Drivers
Commonly known as the BA driver, it works by sending current through a coil which causes the armature to vibrate in the magnetic field. This vibration then causes a drive pin to move and vibrates a membrane in the driver, creating sound pressure. This sound pressure is then released through the sound outlet and usually funneled through a plastic tubing to the nozzle of the earphone, which is then picked up by our ears. Usually used to produce clear and accurate mid-range sounds like vocals, guitars, drums and such.
Balanced armature driver and its components (Image taken from Sonion)
As opposed to dynamic drivers, BA drivers are usually very snappy in their response, which means that your music does not sound very cluttered as it is sensitive to changes in the music. However, as the sound is usually funneled through a plastic tubing, the music produced may not sound as wide (i.e. narrow soundstage) and can sound "sharp" (sibilant) as the sound would reflect off the tubing (causing resonance with the tubing) before reaching our ears.
The interesting thing about BA drivers is that it is unable to handle a wide range of sound well when used independently, but pairing it with multiple BA drivers allows it to split the workload and provide better separation and detail retrieval. Hence, you may have noticed some earphones having "multi-BA" or "multi-driver" setup, fitting from 2 to even 18 drivers into each side of an earphone.
That isn't to say that the more BA drivers it has, the better it'll sound, it is still ultimately dependent on the tuning of the sound. BA drivers also tend to produce very rumbly bass but it does not have a very deep bass extension and differs from that produced by dynamic drivers.
Sound Characteristic :
- Clear accurate mids
- Fast; usually does not sound "cluttered" when having to work with multiple instruments
- When used to produce bass, bass is not deep
- Can sound sharp (sibilant) depending on tuning and how sensitive one is to treble
- Might need multiple BA drivers for earphone to perform better
Electrostatic and Piezoelectric Drivers
In the earphone scene, electrostatic drivers (or electrostats) are a fairly new technology though it has been used in headphones since many years back such as in Stax headphones.
Electrostatic Driver (Image taken from Wikipedia)
This driver works by vibrating a thin diaphragm between a pair of metal plates, causing it to be very sensitive to changes in the current and producing very accurate sounds.
From personal experience, these drivers produce the most accurate treble I have heard as compared to the others mentioned. They also usually require a lot of power to drive them, having to crank up the volume much more than other earphones.
One point to note is that there is the existence of "piezoelectric" drivers, they work differently than electrostatic drivers but the sound characteristics are similar to that of electrostats and costs lesser, though not as accurate.
Sound characteristic :
- Accurate and clear treble
- Fast; reacts to changes in frequencies very quickly
- May sound sharp (sibilant) to most people or people sensitive to treble
- (As of now) Costs a lot to have them implemented in earphones
- Usually requires a lot of power to drive them
You might be wondering "Hey they seem to be good in each individual segment of an audio, why not put them all together then?" and you are right. These setups are known as "Hybrid" setups, which means combining 2 or all of the above mentioned drivers into one earphone. Audio companies have been experimenting with getting the best quality audio to their customers and for many years and the standard hybrid setup was that of Dynamic drivers for bass and BA drivers for highs and mids.
Then with the release of electrostats, it changed the game entirely for highs and now they are starting to incorporate one of each type of driver in the earphone : Electrostats for highs, BA for mids and Dynamic for lows as can be seen in more recent offerings such as the Shuoer EJ07 and Fir Audio M5. However, hybrids usually cost much more (usually in the hundreds of dollars at least) and are generally harder to drive than standard earphones, requiring a lot of power from your audio player.
Given the varying types of earphone drivers in the market, there is no single "best" driver type for any genre. Do remember that the sound produced by a driver is also dependent on how the tuning is done for each earphone, so take this guide with a pinch of salt and try them out first before judging an earphone by its drivers (and driver count). Hope this guide helps you to briefly understand what type of sound each driver is generally good at producing.