Other players in this field – such as USound GmbH might disagree (see ST, USound demo MEMS-based speakers in headphones) – but xMEMS has its rationale.
The xMEMS argument runs that others have replaced the voice coil actuator with a MEMS actuator but the rest of the speaker is constructed much as before and is as complicated as before. What xMEMS has done is to make whole of the speaker; actuator membrane and enclosure as a packaged MEMS device, bringing all the advantages of semiconductor foundry manufacturing and packaging to bear on the problem.
The result is a scalable, all-silicon speaker for near-field audio in sealed earbuds and closed headphones and can operate as a tweeter for unsealed headphones. The unit is based on PZT piezo MEMS material.
The startup is fabless and uses one the largest pure-play foundries and their piezoMEMS process as well as a standard assembly and test company to produce devices. The company, which is backed by Techlink Ventures amongst others, is not revealing the name of the foundry.
The device has a full audio bandwidth from 10Hz up to 20kHz and the six-cell configuration produces a sound pressure level (SPL) of 115dB with total harmonic distortion across the range above 200Hz of 0.5 percent.
Advantages over voice coil and balanced armature type speakers are: spatial volume, power consumption of 42microwatts and latency below 0.1ms. The fast response makes for considerably better active noise cancellation. The use of MEMS membranes makes for water- and dust-proof.
The basic top-firing package is 8.4mm by 6.05mm by 0.985mm. xMEMS is also offering a side-firing MEMS measuring 6.05mm by 1.0mm by 8.4mm.
Mike Housholder, vice president of marketing and business development for xMEMS, said the company received first silicon back in April 2020 and is offering early samples to customers this month (July). First commercial orders are due to be supported from February 2021 with mass production ramping up through the year.
Next: Goodbye, voice-coil
The company was founded by October 2017 by a team of MEMS veterans and audio industry engineers with experience gained at Apple, InvenSense, Knowles and UltraChip. Company co-founder and CEO Joseph Jiang was previously a vice president at Knowles Corp. and before that was a vice president of business development at TDK-InvenSense.
The company has developed an all-silicon scalable speaker for near-field audio in sealed earbuds and closed headphones and can operate as a tweeter for unsealed headphones. The company has raised about $11 million to date through a mix of venture capital and angel investors, Housholder said.
“This use of repeating cells makes this a scalable architecture. The six-cell produces enough SPL for TWS ear-buds, in-ear monitors or over-the-ear headphones. These are near-field designs but free-space audio is on our roadmap.”
Housholder points out another couple of advantages of the MEMS speaker. One is shock resistance; 10,000-g for the MEMS speaker versus 3,000-g for voice-coil speakers. The second is consistency of manufacturing. It is perhaps not well-known that voice-coil speakers have to be listened to and matched to make up balanced headsets. The MEMS manufacturing process is so consistent it can avoid that step.
Housholder wouldn’t be drawn on pricing except to say that while Montara is superior on a number of fronts to voice-coil units it would be competitive on price.
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