There are two different sound-producing technologies used in in-ear earbuds. Here’s what they are, how they differ in construction, and their ability to reproduce sound.
The two primary sound reproduction technologies used in earbuds and in-ear monitors (IEMs) are Dynamic Drivers and Balanced Armature. Both of these are sound-producing devices similar in many ways to small speakers. The difference in how they are constructed also determines how their frequency response will be skewed.
Dynamic Drivers are prevalent in earbud-type earphones. They are similar in construction to miniaturized speakers, with a voice coil driving a membrane that’s the equivalent of a tiny speaker cone. Of course, the size and mass of the membrane being driven determines the overall frequency response. Dynamic Drivers are very efficient and do not need much input to produce high volume.
In general, earphones with a dynamic driver may be slightly larger than those using Balanced Armature. This larger size frequently enhances the bass response of the earphone, giving punchy bass, but rolling off a bit on the higher frequencies. So if you’re looking for more bass rather than a somewhat flatter frequency response, you might want to consider an IEM with dynamic drivers or an earphone that contains a combination of a dynamic driver and one or more Balanced Armature drivers.
A second popular sound-producing technology is the Balanced Armature driver. Widely used in in-ear hearing aids, a balanced armature driver consists of a reed-like metal armature placed inside a voice coil and balanced between two magnets. These magnets suspend the voice coil, and the armature is attached to the center of the diaphragm.
Like an audio speaker or Dynamic Driver, current passing through the voice coil causes the armature to vibrate. Attached to the armature on one end is a piston-like push rod that transfers the vibrations from the armature to a diaphragm, causing the diaphragm to vibrate and produce sound. The armature doesn’t have a lot of mass, so it can vibrate easily at higher frequencies.
While some earphones use dynamic drivers, many vendors’ top-of-the-line models use balanced armature technology for several reasons. One is that the balanced armature drivers are very small, so more than one can fit in the small earpiece. For example, Campfire Audio’s Andromeda 2020 IEMs use five balanced armature drivers.
These multiple drivers are tuned to work at a different range of frequencies, ensuring a better frequency response throughout the audible range and providing a very flat and balanced sound. Ultimate Ears IEMs use between three and eight balanced armature drivers. And their models vary from flat and balanced to enhanced response in specific frequency bands. And both vendors, and others, have models that combine dynamic drivers and balanced armatures.
Finally, balanced armatures are very efficient, which means you get louder sound at lower power settings. In fact, Campfire Audio warns its users that their normal loudness settings may be too loud and to dial back the power until they see how the IEMs respond at different power settings.
On the other hand, numerous high-quality earphones use dynamic drivers, such as the Sennheiser IE 500 Pro. These $600 phones use a single 7mm dynamic driver. As a general rule, earphones using dynamic driver technology mount only a single driver in the housing due to the driver’s larger size compared to a balanced armature driver.
However, sometimes, a smaller dynamic driver is used along with one or more balanced armature drivers to provide a slightly skewed response on the bass end of the audio spectrum. Because of the larger diaphragm that produces the sound, a dynamic driver-based earphone or a hybrid earphone of IEM will generally have a punchier bass than an earphone with only balanced armature drivers, whose response tends to be flat across the entire audible frequency spectrum.
Ken Ball, the CEO and Chief Designer at Campfire Audio, which makes high-end earphones and in-ear monitors, describes the strengths of Dynamic Drivers this way. “Dynamic drivers, in my opinion, are generally more lush sounding. The low and mids are generally its strong suit; it’s warmer, has, I think, a very good ambiance feeling mood. It’s musical, has good bloom, the decays are quite good, and the imaging is very good. It has a lush, rich sound; it’s a smooth sound, so it’s free from a lot of irritants; the sound stage is quite good. On the other hand, it’s got some weaknesses too. Dynamic drivers can be soft and sometimes kind of mushy. It doesn’t excel in high frequency like a Balanced Armature does.”
And earphones or monitors with multiple drivers also have a crossover circuit that divides the incoming electrical signal and routes a certain range of frequencies to a driver fabricated to be most efficient in that range. For example, you might have three Balance Armature drivers in an earphone or IEM, with one driver efficiently reproducing high frequencies, one for the mid-frequencies, and a third for the bass. The crossover sends that part of the incoming signal to the driver that will best reproduce it.
There is a downside to using only balanced armature drivers. They are not as efficient at lower bass frequencies as dynamic drivers, resulting in less bass production. Users who desire a more bass-oriented sound might want to explore a hybrid IEM with balanced armature and dynamic drivers. An example of this approach is Ultimate Ears’ UE 6 Pro, which contains two neodymium dynamic drivers and a balanced armature driver.
Knowing what the driver makeup is in earphones or in-ear monitors can help you choose. If you prefer a flat response over the audio spectrum, consider phones with one or more balanced armature drivers. Depending on the vendor, this type of phone is generally an in-ear monitor and can contain up to eight balanced armature drivers.
If you’re looking for heavier performance in the lower registers, you could consider models using dynamic drivers or a hybrid model containing both types of drivers.
Of course, internal construction is just one of the points to consider. Price is also important. Many in-ear monitors use one or another technology or a hybrid using both technologies and cost from $500 or so up to the thousands. The type of driver(s) used doesn’t necessarily lock a pair of phones into a particular price range. For example, 1More has a pair of earphones that feature three balanced armature drives and a dynamic driver for about $150.
And while knowing how the technology works and affects sound reproduction is nice, it’s far more likely that price, rather than technology, is going to be one of the major factors in your purchase decision.