xMEMS’ All-silicon, Solid-state Fidelity Micro Speakers Now Available
These speakers are said to offer higher performance in a smaller size, bringing high-fidelity audio to new applications.
High-fidlity audio company xMEMS has announced the general availability of three silicon-based speaker solutions for integration in the next generation of audio devices. This announcement comes after the company's 2023 reveal of Montara Plus and Skyline MEMS speakers, completing the solid-state audio trinity alongside the Cowell device.
An example device using the Montara Plus speaker allows for high output in a small form factor, making it useful for in-ear monitors (IEMs). Image used courtesy of xMEMS
Each speaker brings unique benefits to the designer, but they all rely on a solid-state design versus traditional coil-and-magnet architectures. And while solid-state speakers are not a new idea, the benefits for compact devices are vast. This article examines the differences between solid-state and coil-and-magnet architectures and the specific performance specs of the three newly available xMEMS devices. In addition, we'll discuss the future of solid-state speakers to determine how and where they may be found in the future.
All-silicon Audio
Typical coil-and-magnet speakers leverage a permanent magnet and a coil to produce the physical motion required for sound waves. Because the induced field is proportional to the coil’s current, the coil and magnet rely on a high current to create a large response. In addition, the natural frequency of these speakers coincides with human hearing, introducing several undesired effects such as breakup.
The coil-and-magnet speaker uses a coil combined with a permanent magnet to induce motion in the cone, producing sound waves. Image used courtesy of Audiofanzine
Solid-state speakers, on the other hand, leverage the stiffness of silicon to push the frequency range of breakup past the range of human hearing, improving the fidelity of the speaker. In addition, piezo-driven speakers exhibit better pulse response due to the increased natural frequency. They are also easily manufactured at scale.
MEMS-based speakers offer several audio improvements due to the improved coverage of the piezo actuator. Image used courtesy of xMEMS
xMEMS’ Micro-audio Devices
xMEMS is currently offering three MEMS-based audio devices, all of which offer unique advantages. The oldest device, dubbed Cowell, targets true-wireless sound (TWS) and hearing aid applications and offers up to 110 dB SPL at 1 kHz. These target applications were likely selected due to the device’s improved performance versus size, allowing for increased area efficiency and room for receiver electronics.
The next xMEMS device is the Skyline, designed to combine the benefits of open- and closed-fit earbuds. This device uses DynamicVent technology, which can be user-controlled to provide noise cancellation or transparency at will. In addition, the programmable vent improves audio and passthrough performance and reduces the effects of occlusion on the user’s experience.
The xMEMS' Skyline device targets adaptive cancellation/transparency applications, thanks to the Skyline vent. Image used courtesy of xMEMS
Finally, the Montara Plus provides the “world’s highest output” for a MEMS speaker, clocking in at 120 dB SPL at 200 Hz. The Montara Plus also provides a full-bandwidth response, making it useful for high-fidelity yet compact IEMs for audiophile-grade applications.
High-fidelity Audio at the Silicon Level
xMEMS has partnered with a pure foundry MEMS manufacturer to make its devices generally available. The benefits of silicon-level integration may ultimately benefit designers, allowing them to leverage reliable semiconductor tech to reduce calibration requirements.
Designers may now have an extra tool in their toolbelt as miniature speakers and wireless audio devices become more commonplace. From preliminary results, it seems that solid-state speakers may have sufficient advantages to capture more of the high-fidelity audio market. As engineers include devices like those of xMEMS in their designs, more performance data will become available to compare these devices to existing audio architectures.
