Dynamic vs Balanced Armature Driver
As with most things in the world of high-end audio, there are a multitude of options available, with each manufacturer trying to claim that their approach is the ultimate solution. In fact, between some of the misinformation online and other wildly optimistic marketing claims by the manufacturers, it’s incredibly easy to become totally overwhelmed with the flood of info. But really, things aren’t quite as complex as it may seem, and for the large part it usually just comes down to preference and a manufacturer’s expertise.
When it comes to IEMs (in-ear monitors) there are 3 different driver technologies used, namely dynamic, balanced armature, and planar magnetic. Planar magnetic have been around for a while, but mainly in full-sized speaker systems and headphones. It’s only very recently that they’ve started making an appearance in IEMs. As such, let’s put the spotlight of this discussion on the differences between dynamic and balanced armature drivers only.
How do they work?
Dynamic drivers are your your standard speaker drivers. It consists of a cone (also called a diaphragm), a voice coil, and a set of magnets. As an electrical current is passed through the voice coil it generates a magnetic field, and this generated magnetic field interacts with the set of magnets that surround the voice coil. Thus, by changing the direction of the current flowing through the voice coil, the polarity of the generated magnetic field changes, and this constant change of current flow results in the voice coil (and ultimately the speaker cone) being attracted to or pushed away from the set of magnets.
Of course, in the context of IEMs, it’s just a really, really small speaker.
Putting it all into context
Ok, so that’s how they work, but what does that mean for portable audio? Well, as you might imagine, each approach has its own pros and cons. As mentioned, BAs can be prone to resonance. Also, whilst their efficiency and electrical sensitivity means that they don’t require a very powerful amplifier, it also means that they’re prone to outputting hiss from an amplifier. BAs are also really, really small, which is why you’ll often see manufacturers going totally nuts and stuffing a gazillion of them into each IEM.
On the flip-side of the coin, dynamic drivers tend to be less efficient, but as such they’re also less prone to hiss. The way they move air also tends to give dynamic drivers a deeper and richer bass response, whereas BAs tend to have greater response at high frequencies. For this reason, it’s not uncommon to see hybrid setups – where both a dynamic driver and one or more BAs are incorporated. Fiio, for example, opted for a triple-hybrid design with their F9-series by employing a single dynamic driver and 2 BAs. On the other hand, In Ear went for 8 BA drivers per ear piece for their fantastic ProPhile 8, where as 64 Audio took thing even further and placed 18 drivers in each earpiece of their U18t.
READ: Fiio F9 In Ear Headphones Review
The need for multi-driver configurations
So why is there even a need for multi-driver setups? Strictly speaking, there isn’t. Heck, a lot of times it’s just for bragging rights, but there is some slight merit to it too.
As mentioned, due to the resonance issues of BAs, their response over the audible frequency range is rather erratic. As such, a manufacturer might use multiple BAs, and then also incorporate elaborate crossover networks to cut-off the audio signal to specific BA drivers above and below certain frequency. For example, if a BA driver has a really poor response between 20 and 2kHz, a great response from 2.5kHz to 6kHz, and then again a poor response from 7kHz to 20kHz, the manufacturer will most likely create a crossover so that that specific BA only receives audio signals that fall within the 2kHz to 6.5kHz range.
Of course, the advantage of using a single driver (whether it is a dynamic or BA) is that it’s a simple setup, which means that manufacturing cost and time is kept low.
Perhaps the biggest advantage of using a single driver, however, is that you keep the sound coherent. What exactly do we mean by this? Take a look at the image below.
What we have here is a simple sine wave. However, whilst all sound is a wave, the natural sound that we hear isn’t as simple as just a single frequency sine wave, instead it is a combination of a multitude of different sound waves which all interact with one another to create a far more mathematically complex wave pattern.
Below is a look at a typical audio file, in this case we’re looking at Livingston Taylor’s Isn’t She Lovely? form his Ink album.
As you can see, it’s far more erratic and complex than a simple sine wave. Zooming in on a portion of the music allows us to see that complex wave pattern. But, just like the simple sine wave, the entire wave still oscillates between a maximum of +1 and -1.
The important thing to note here is that, whilst the music’s wave pattern is the sum of a multitude of different sine waves, the result is still just a single wave pattern, and this pattern is also a representation of how a driver will move.
And here in lies the problem with multi-driver setups – when creating a crossover network, you’re splitting the audio signal up into new and different wave patterns, then each driver plays its designated pattern, and then each of those patterns collide and interact with one another before hitting your eardrum.
So, the problem here is that we have absolutely no guarantee that once those new wave patterns combine that it will once again be a true representative of what the original wave pattern was supposed to be. This is arguably the biggest challenge when creating multi-driver IEMs. Strictly speaking, if a DAC, AMP, or driver is changing the wave pattern at all, then we are losing fidelity. Heck the whole point behind Hi-Fi (high fidelity) is an attempt to reproduce the most faithfully accurate audio signal; to try and get the sound you’re hearing to be as close to how it sounded in the recording setting.
So obviously dynamic is best…
Well, not necessarily. Dynamic drivers also aren’t perfect, and all of the above info is largely based on theory. The thing to remember here is that theory doesn’t always translate into exact reality. A really well-designed multi-BA setup will easily outperform a poorly designed single dynamic driver setup. But, creating a genuinely great performing single dynamic driver IEM is less complex and perhaps more cost effective.
Really, the best thing to do when deciding whether to buy an IEM with a dynamic, BA, or hybrid-driver configuration is to try each of them for yourself, i.e get whatever sounds best to you. But, of course, our world has changed, and the way we purchase products has changed too. For many people they simply don’t have access to a brick-and-mortar shop in order to physically try an item for themselves. As such, we very often rely on info on the web. So, if it’s not possible to try an item for yourself, check out reviews and especially third-party measurements of the various performance parameters. But don’t be fooled into thinking that more drivers MUST mean better audio quality.
