If you have a pair of in-ear headphones, there’s a good chance they're using a technology that’s several decades old. Despite attempts to introduce different, exotic-sounding systems like planar magnetic, electrostatic and even bone conduction, most IEMs or in-ear headphones still use either balanced armature or dynamic drivers. But there’s another contender, promising high fidelity, low power consumption and a tiny physical footprint. The twist is, it’s a technology that’s been in your pocket for 10 years already.
We’re talking about micro-electromechanical systems (MEMS), and it’s a technology that’s been used in almost every microphone in every cell phone since the 2010s. When applied to headphone drivers (the inverse of a microphone), the benefits are many. But until recently, the technology wasn’t mature enough for mainstream headphones. California-based xMEMS is one company pushing the technology and consumer products featuring its solid-state MEMS drivers are finally coming to market. We tested the high-end Oni from Singularity, but Creative has also confirmed a set of TWS headphones with xMEMS drivers will be available in time for the holidays.
Where conventional speakers and drivers typically use magnets and coils, MEMS uses piezos and silicon. The result, if the hype is to be believed, is something that’s more responsive, more durable and with consistent fidelity. And unlike balanced-armature or dynamic, MEMS drivers can be built on a production line with minimal-to-no need for calibration or driver matching, streamlining their production. xMEMS, for example, has partnered with TSMC, one of the largest producers of microprocessors for its manufacturing process.
Of course, MEMS drivers lend themselves to any wearable that produces sound from AR glasses to VR goggles and hearing aids. For most of us, though, it's headphones where we’re going to see the biggest impact. Not least because the potential consistency and precision of MEMS should marry perfectly with related technologies such as spatial audio where fast response times and perfect phase matching (two headphones being perfectly calibrated to each other) is essential.
For now, MEMS is best suited to earbuds, IEMS and TWS-style headphones but xMEMS hopes to change that. “The North Star of the company was to reinvent loudspeakers,” Mike Householder, Marketing & Business Development at the company told Engadget. “But to generate that full bandwidth audio in free air is a little bit more of a development challenge that's going to take some more time. The easier lift for us was to get into personal audio and that's the product that we have today.”
To look at, the first IEM to feature xMEMS’ solid-state drivers, Singularity’s Oni, seem like regular, stylish high-end in-ear monitors. Once the music started to flow, though, there was a very clear difference. Electronic genres sounded crisp and impactful in a way that feld more. The MEMS drivers’ fast transient response evidenced in the sharp, punch percussion of RJD2’s “Ghostwriter” and the Chemical Brothers’ “Live Again.” The latter’s mid- and high-end sections in particular shone through with remarkable clarity. Bass response was good, especially in the lower-mids, but perhaps not the strong point of the experience.
When I tried Metallica’s “For Whom the Bell Tolls,” I immediately noticed the hi-hats pushing through in a way I’d never heard before. The only way I can describe it is “splashy.” It didn’t sound weird, just noticeable. I asked Householder about this and he wasn’t as surprised. “Yeah, the hi-hats, cymbals and percussion, you're gonna hear it with a new level of detail that you're really not accustomed to.” He said, adding that some of this will be the tuning of the supplied headphone amplifier (made by iFi) so it’s partly the EQ of that, mixed with the improved clarity of high frequencies from the MEMS drivers.
There was another surprise with the supplied amp/DAC, too: It had a specific “xMEMS” mode. I originally planned to use my own, but it turns out that I needed this specific DAC as the MEMS drivers require a 10-volt bias to work. I asked Householder if all headphones would require a DAC (effectively ending their chances of mainstream adoption), but apparently xMEMS has developed its own amp “chip” that can both drive the speakers and supply the 10-volt bias. The forthcoming True Wireless buds from Creative, for example, obviously won’t need any additional hardware.
This is where things get interesting. While we don't know the price for Creative’s TWS buds with xMEMS drivers, we can be sure that they will be a lot cheaper than Singularity’s IEMs which retail for $1,500. “You know, they're appealing to a certain consumer, but you could just very easily put that same speaker into a plastic shell, and retail it for 150 bucks,” Householder told Engadget. The idea that xMEMS can democratize personal audio at every price point is a bold one. Not least because most audiophiles aren’t used to seeing the exact same technology in their IEMs also in sub-$200 wireless products. Until we have another set to test, though, we can’t comment on the individual character each manufacturer can imbue on them.
One possible differentiating factor for higher-end products (and competing MEMS-based products) is something xMEMS is calling “Skyline.” Householder described it as a dynamic “vent” that can be opened and closed depending on the listener’s needs. Similar to how open-back headphones are favored by some for their acoustic qualities, xMEMS-powered IEMs could include Skyline that would open and close to prevent occlusion, improve passive noise canceling and other acoustic qualities such as “transparency” mode where you want to temporarily let external, environmental noises come through.
For those who prefer on-ear or over-ear headphones, MEMS technology will likely be paired with legacy dynamic drivers, at least initially. “The first step that we're taking into headphone is actually a two-way approach,” Householder said. The idea being that a smaller dynamic driver can handle the low frequencies, while MEMS drivers currently don’t scale up so well. “It's really the perfect pairing. The dynamic for the low end, let it do what it does best, and then we've got the far superior high frequency response [from MEMS],” he said. “But the long term vision is to eventually fully replace that dynamic driver.”
The ultimate goal would, of course, be a set of solid-state desktop speakers, but we’re a ways out on that, it seems. For now, though, there’s a tantalizing promise that MEMS-based in-ears could modernize and maybe even democratize consumer audio, at least around a certain price point. Not to mention that xMEMS isn’t the only company in the game. The Austrian startup Usound already showed its own reference-design earphone last year and Sonic Edge has developed its own MEMS “speaker-in-chip” technology. With some competition in the market, there’s hope that the number of products featuring it will increase and improve steadily over the next year or so.