These days it’s hard to not come across solid-state (micro-electromechanical systems, MEMS) microphones, as they are now displacing electret microphones almost everywhere due to their small size and low cost. Although MEMS speakers are not impossible, creating a miniature speaker that can both displace a lot of air (‘volume’) and accurately reproduce a wide range of frequencies – unlike simple piezo buzzers – is a lot tougher. Here a startup called xMEMS figures that they have at least partially cracked the code with their piezoMEMS speakers, with Creative using the Cowell version in their brand-new Aurvana Ace in-ear monitors.
The Cowell is a full-range speaker, but its sound pressure level (SPL) is not sufficient (~111 dB @ 1 kHz) for use in an active-noise cancelling, which is why the Aurvana Ace also includes a traditional 10 mm driver. The likely successor in the form of Cypress is a small (6.5 x 6.3 x 1.65 mm) package that claims to reach an SPL of 143 dB at 20 Hz, which might be able to handle IEM ANC duty by itself.
According to xMEMS, what enabled the performance of these MEMS speakers is the use of silicon membranes (flaps) along with the piezo elements. These structures can be made out with some degree of clarity on the speakers, and according to early hands-on tests of the Aurvana Ace, audio quality is very good. Since with this first product the MEMS speaker mostly handles the high-end, the overall audio reproduction is a combination of the dynamic driver, the MEMS speaker and the DSP magic that glues it all together, so it’s hardly a fair assessment of the technology, but it will be interesting to see where it goes from here. Who doesn’t want to have a feather-light, 1×1 meter PCB that’s a wafer-thin 1 500 Watt RMS-level speaker, or just laptop speakers that don’t sound terrible?
Top image: XMems Cowell MEMS-based tweeter on top of dynamic driver. (Credit: xMEMS)