Ultrasonic MEMS speakers are designed to make useful audio possible in thinner wearables, including watches and fitness bands. xMEMS’s approach modulates ultrasonic air pulses with an audio signal so the air produces audible sound; it is not simply a conventional speaker shrunk down. The idea addresses real packaging constraints, but published performance figures are vendor claims, and a tiny speaker alone cannot guarantee loud, private, bass-rich audio from a watch.
Why speakers are hard to fit in a watch
A conventional dynamic micro-speaker uses a magnet, voice coil and diaphragm. To produce sound—especially bass—the diaphragm must move enough air. Shrinking the driver and its enclosure limits that excursion and the acoustic volume available behind it; reducing thickness can therefore make low-frequency output particularly difficult.
Watches add a distance problem: the speaker is on the wrist, not beside the ear. Open-air designs cannot rely on a sealed ear canal to improve perceived bass or efficiency, and their output must compete with ambient noise while minimizing power draw. The speaker also competes for space with the battery, antennas, microphones, sensors, processors and other components. The EE Times article behind this topic describes conventional micro-speakers as commonly about 3 mm thick, a broad design comparison rather than a universal specification. The article is labeled Partner Content and was written by xMEMS marketing executive Mike Housholder, so its comparisons should be read as vendor-sponsored claims (EE Times, June 10, 2025).
What MEMS changes
MEMS means microelectromechanical systems: miniature mechanical structures made using semiconductor-style manufacturing processes. xMEMS describes its speaker platform as solid-state and all-silicon. That construction can support compact packages and repeatable device geometry, potentially improving left/right consistency and reducing unit-to-unit mechanical variation.
MEMS does not automatically mean full-range sound. Earlier MEMS speakers were often used mainly as tweeters because limited mechanical displacement made low-frequency output challenging. The xMEMS approach discussed here changes how audible sound is generated rather than simply asking a tiny structure to reproduce every audible frequency through large diaphragm motion.
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How “sound from ultrasound” works
- Audio is encoded: The audio waveform modulates an ultrasonic carrier or pulse stream.
- The MEMS device emits pulses: Its transducer creates ultrasonic pressure variations in the air.
- The air demodulates them: Nonlinear behavior in air converts the modulated ultrasonic energy into audible pressure variations.
- The listener hears the audio: The intended result is ordinary audible content, not a separate ultrasonic tone.
This is xMEMS’s description of its architecture, not a general account of every ultrasonic audio system. The distinction matters: the transducer is not simply trying to move a conventional diaphragm back and forth at a low audible frequency such as 40 Hz. But ultrasound does not repeal acoustic or electrical limits. Useful low-frequency pressure still depends on drive power, modulation, enclosure and port design, distance, orientation and the listening environment. xMEMS explains the approach in its Cypress and Alta2 announcement.
Sycamore-W is the watch-focused design
xMEMS’s Sycamore-W is a long, narrow speaker package intended for smartwatches and fitness bands. Its listed dimensions are 20.0 × 4.0 × 1.28 mm, and xMEMS gives its mass as approximately 150 mg. The company says the package reduces volume by about 70% versus its relevant legacy design target. That comparison concerns package volume, not the size of the complete audio subsystem or a finished watch.
The elongated shape may suit a watch cavity where a compact rectangular component would conflict with the battery, sensors or other hardware. xMEMS also claims component-level IP58 protection and 10,000g mechanical shock resistance; neither claim establishes the finished watch’s water or shock rating. The company announced Sycamore-W on May 13, 2025, with volume production targeted for Q2 2026. That was a company forecast, not independent confirmation of production scale or device availability (xMEMS announcement).
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Sycamore and Cypress serve different acoustic jobs
Sycamore is the open-air, near-field product family relevant to watches, glasses and other wearables. Cypress is intended for occluded or in-ear ANC true-wireless earbuds, where the earbud’s fit and sealed acoustic path change the problem substantially. Cypress is paired with xMEMS’s Alta2 companion drive ASIC, a reminder that the ultrasonic speaker is not necessarily a drop-in replacement for a dynamic driver.
| Product | Intended application | Acoustic setting | Published package details |
|---|---|---|---|
| Sycamore | Glasses, watches, open-fit earbuds, XR devices, phones and laptops | Near-field, open-air or open-fit | 8.41 × 9.0 × 1.13 mm; approximately 150 mg, according to xMEMS |
| Sycamore-W | Smartwatches and fitness bands | Wrist-worn near-field use | 20.0 × 4.0 × 1.28 mm; approximately 150 mg, according to xMEMS |
| Cypress | ANC true-wireless earbuds | Occluded/in-ear | 6.5 × 6.3 × 1.65 mm on the xMEMS product page; paired with Alta2 |
Sycamore specifications are listed on the xMEMS loudspeaker page; its open-air applications and mass are also described in the Sycamore introduction. Cypress’s dimensions appear on the xMEMS speaker page. Its low-frequency SPL claim applies to Cypress, not to Sycamore in a watch.
What the performance claims establish—and what they do not
The EE Times partner article reports xMEMS comparisons claiming about 11 dB greater SPL at 40 Hz and 15 dB greater SPL at 5 kHz than “leading” open-wireless-stereo earphones. It also reports at least 90 dB at the highest frequencies in a tweeter-style application, near-zero phase shift, IP58 protection and roughly one-third the thickness and one-seventh the overall size of conventional dynamic-driver designs. These are company-reported figures, not independently established results.
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The article does not disclose enough test detail to treat those numbers as universal: it does not provide a complete independent protocol, comparison-product list, measurement distance, enclosure, amplifier power, equalization, sample size or measurement standard. In open-air audio, those conditions can materially change the result. A reported SPL advantage at selected frequencies does not by itself establish better overall sound, lower power consumption, less distortion or a similar experience on a wrist.
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xMEMS’s product page characterizes Sycamore’s low-frequency behavior as approximately a first-order 1/f decay, compared with the 1/f² behavior it associates with dynamic drivers over a stated range. That is a company characterization of response behavior, not a standalone guarantee of stronger perceived bass. The product page also lists the package dimensions and component-level protection claim.
Why phase and manufacturing consistency matter
Closely matched left and right speakers can make calibration easier. Consistent phase behavior may help system designers working on beamforming, spatial audio, transparency modes or leakage-reduction processing. Semiconductor-style fabrication may also reduce the per-unit variation that otherwise drives individual tuning.
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Those benefits are conditional. Spatial performance and privacy also depend on speaker placement, microphones, DSP, fit, orientation, frame or case acoustics, ambient noise and listening level. A matched pair cannot compensate for poor geometry or a weak algorithm, and phase consistency by itself does not prevent sound from reaching bystanders.
Open-air audio still has limits
- Leakage: Open-air speakers do not isolate the listener like a sealed earbud; nearby people may hear the content.
- Distance: Bass perception and intelligibility are sensitive to the distance and orientation between speaker and ear. A glasses temple near the ear and a speaker on the wrist are not equivalent use cases.
- Environment: Outdoor noise can force higher playback levels, affecting intelligibility, privacy and battery life.
- Integration: A 1-mm-class speaker does not make the entire audio system 1 mm thick. The driver electronics, power management, DSP, acoustic openings, protective mesh, mounting and enclosure also take space.
- Protection: A component-level IP58 claim does not assign that rating to a completed watch. The enclosure and every opening, seal, port and assembly interface determine product-level protection.
What a watch maker should evaluate
The meaningful comparison is between complete audio systems in the intended watch—not bare package dimensions. Before committing to a design, an OEM should establish the following under representative conditions:
- Acoustics: SPL at realistic ear distances, frequency response in the final case, bass distortion, transient response, leakage and sensitivity to wrist position.
- Power: Drive voltage, normal and peak consumption, sustained-output thermal behavior and battery impact at defined loudness and duty cycle.
- Integration: Required driver ASIC, DSP and calibration; port, mesh and back-volume needs; mechanical mounting and tolerance to sweat, dust, vibration and shock.
- User experience: Intelligibility for calls, navigation and alerts in noise; acceptable music quality; and whether output can be heard by others nearby.
- Production readiness: Sampling and allocation, acoustic yield, reliability and qualification data, supply capacity, test fixtures, reference designs and volume pricing.
For Sycamore-W specifically, the public information cited here does not establish detailed electrical requirements, a full reference design, independent system measurements, production volume or public pricing. Those are design-in questions for the vendor and its integration partners, not details that can be inferred from package size.
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Commercial status: a component platform, not a retail watch feature
xMEMS introduced Sycamore in November 2024, with sampling planned for Q1 2025 and mass production beginning in October 2025 according to its announcement. Sycamore-W’s Q2 2026 volume-production target was another company forecast. The cited public sources do not independently establish actual production volumes, design wins, yield, shipment scale or broad availability in consumer watches as of August 16, 2026.
For Cypress, xMEMS announced mass-production readiness in September 2025 and said customer mass-production shipments were expected in 2026. That announcement is about the in-ear product and does not establish Sycamore-W’s commercial status. A separate Rayking partnership announcement describes a Cypress-and-Alta2 module for earbud integration, not a turnkey watch module.
This is a business-to-business component technology: the cited product pages are not retail listings for a finished watch, and they provide no public component price. A watch maker evaluating it would need to request engineering information and assess samples in its own enclosure against a conventional dynamic speaker, which remains the mature alternative with established supply and integration practices.
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What would make the technology convincing for watches?
The key question is not whether an ultrasonic MEMS device can fit into a thin package; the published dimensions make that proposition concrete. The harder test is whether a finished watch can meet its acoustic, battery, privacy and reliability targets at the wearer’s ear across real listening positions and environments. Until comparable, independently documented system measurements and commercial deployment data are available, the strongest case for Sycamore-W is space-efficient design potential—not proof that it will outperform conventional speakers in every watch.
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