
xMEMS announces the first monolithic MEMS speaker - rbanffy
https://www.anandtech.com/show/15894/xmems-announces-worlds-first-monolithic-mems-speaker
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shard
Just to be clear, this seems to be the first _monolithic_ MEMS speaker, which
I take to mean that the speaker array is fabbed as one die, as opposed to each
speaker being a separate piece of silicon. There are already MEMS speakers
available before this. Also, for mobile devices, MEMS have been used for a
long time now, specifically for the microphone and IMU (inertial measurement
unit -- consisting of accelerometer, gyroscope, magnetic sensor).

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IshKebab
MEMS _speakers_ are not used in phones (in general; I'm sure someone will
nitpick).

A speaker is very different to a microphone.

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dwohnitmok
> A speaker is very different to a microphone.

Is it? I've definitely had fun little experiments where I turn a microphone
into a speaker or use a speaker as a microphone. It's just a matter of whether
I'm powering the membrane or whether the membrane is powering me, i.e. its
just a matter of which side of the mechanism I sit on. It's a conversion
between electricity and mechanical vibration that can be driven from either
side.

I'm sure there's a lot of engineering trade-offs that change if you're looking
to optimize for recording fidelity vs output fidelity, so the details of their
implementation are probably quite different, but at their core the two don't
seem all that different.

Maybe they're totally different in the MEMS world?

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anamexis
I think the engineering trade-offs are significantly large enough to make
microphones and speakers "totally different" in the conventional, non-MEMS
world.

Sure, at the very core of it, it's just trading electricity for mechanical
vibration, and this functions in both directions. But the engineering that has
gone into specializing both speakers and microphones is staggering.

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the8472
I find it amazing that litography is considered a "simplification of the
manufacturing line" compared to century-old technology that essentially
consists of winding a coil through a magnet. Granted, it's not a bleeding-edge
fab process, but it's still a very strange view that considers this a
simplification.

~~~
quotemstr
Why wouldn't it be? Winding a wire over a coil requires robotics. Making
large, complicated 3D objects is finicky, slow, and expensive. Lithography is
relatively simple --- it's a uniform batch process. Lithography nodes are
complicated and expensive to research --- new nodes require brand new
technology and even science --- but once you have a lithography line set up,
you can run it over and over and over and over again, because the actual batch
process is relatively simple and uniform.

~~~
regularfry
I would suggest hitting up "speaker coil winding" on YouTube if you think this
requires robotics. Sometimes the simplest thing is "pay a human $8/hour". You
don't even need to spend millions on a litho node to make it work.

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willis936
Yes but if you want a million an hour, that’s $8 million/hour. Suddenly
photolithography seems incredibly cheap.

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zaarn
Does it take an hour to wind a coil? Probably not. At worst, a minute for an
experienced worker. That gets you to 130'000 $ per hour and 0.13$ human cost
per device. Though a minute is very optimistic, you don't need that many
windings, if you get it down to 10 seconds, which is a lot of time to wind a
coil, you pay 22'000$ and 0.02$ per product.

That's fairly cheap and if a robot can do it for less becomes questionable
because robots need a lot of maintenance and cost a lot.

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willis936
What if you want 100 billion an hour?

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regularfry
Then you're screwed no matter what process you use. 100 billion 1 gramme
devices is 100,000 tonnes. Per hour.

For reference, that's about half the discharge rate of the Rio Grande.

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phaedrus
At least for coil speakers, arrays of smaller speakers can perform better than
one large speaker (or at least, better than the sum of their parts).

It looks like the ones from the article are meant for earbuds, but if these
MEMS speakers someday become cheap enough to create a large phased array of
them it might make for neat hi-fi system.

~~~
ttul
An array would allow, presumably, for beamforming. Aim the sound precisely at
the listeners’ ears. Stick a camera on each speaker that identifies faces and
beams sound accordingly, leaving those not in the room in near total silence.

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megous
Is that even possible with large part of the hearable spectrum having
wavelengths in meters? How precise would that be?

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seryoiupfurds
Could you transmit ultrasonic carrier waves that intermodulate at the right
spot?

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zaarn
Yes you can, with an ultrasonic transmitter you can create sound in specific
spots or that only a specific listener can hear.

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bashinator
Holosonics.com, or a lot less comfortably,
[LRAD]([https://en.wikipedia.org/wiki/Long_Range_Acoustic_Device](https://en.wikipedia.org/wiki/Long_Range_Acoustic_Device))

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staycoolboy
It claims 20Hz at 90 dB. How in the heck is that possible with such a tiny
device?

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aidenn0
When sealed to the ear-canal, the volume of air needed to be moved to make a
large pressure change is very tiny.

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Matthias247
Right. The metric only makes sense it also a distance is provided at which it
is measured.

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ken47
I'll wait for the 3rd party benchmarks.

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jeffbee
Even the first-party benchmarks look pretty trashy. +20dB peaks at 2k and 10k?
"A bit bright" might understate things. I suppose they intend to equalize this
away with some kind of integrated DSP?

[https://images.anandtech.com/doci/15894/xMEMS%20Montara%20PR...](https://images.anandtech.com/doci/15894/xMEMS%20Montara%20PR%2020062618.png)

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entropicdrifter
It's honestly very easy to counteract big peaks like those at such high
frequencies, especially when you can virtually guarantee that every single
driver will have essentially identical frequency response curves

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jeffbee
Sure, especially if you control the whole package (like a bluetooth headphone
would) and double especially if you can rely on your source material having
zero spectral content above 15k (many streaming music formats) or even lower
(phone calls). But a 20dB cut is pretty dramatic. I use a 5-band parametric
DSP with my headphones and it is only capable of 12dB cuts.

~~~
wtallis
It sounds like "controlling the whole package" is already a foregone
conclusion, given the requirement for a fairly non-standard amplifier.

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bakul
Reminds me of electrostatic loudspeakers.

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jacquesm
Without the high voltages, static buildup, failing power supplies, missing low
end (ok, 200 Hz in this case) and so on. The main similarity is the driver
surfaces are both flat.

~~~
bakul
The main similarity is that they are both voltage modulated capacitive
devices.

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yakz
What does “risk order” mean in terms of manufacturing? It’s on one of the
graphics in the article but for some reason I’m having trouble getting a good
hit for it via Google search.

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ww520
I think it meant to be "risk production." Risk production in chip fabrication
process is the step to produce a batch of chips that's after prototype but
before production. Basically all the specs and designs have been nailed down
and frozen. It's time to go through the manufacture process once to see how
things go before committing to mass production.

~~~
usrusr
Sounds a lot like calling dibs on prototype production that may or may not
yield functional units. The money paid would be financing a later, safer
regular production start date. If they are lucky, the risk buyer can make a
lot of money from the temporary exclusivity and despite talking all the risk
they can still rely on the producer trying their best because they wouldn't
want to risk succeeding too close to the regular production start date because
contracts after that surely define fines for being late.

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jacquesm
Starting at 200 Hz, so you'll need something larger next to it for bass unless
you use clever auditory tricks to supply the missing fundamentals.

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mleonhard
Hopefully these new MEMS speakers will enable wireless headphones with tens of
hours of battery life.

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causality0
Strange. I have a few sets of TWSs and even as a content-addict I've never
come close to draining any of them. The charging cases just have too big a
reserve. My personal wish is for a set without miserable lag so they're useful
for gaming but so far no luck on that front.

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ksec
When something is too good I will always ask, what are the trade offs?

On paper at least, it should be much more reliable than Coil Speaker. And this
is my second MacBook Pro which has Speaker Crackling problem. ( Although it is
more likely an Apple faults judging from Google Search )

~~~
bob1029
Everything in audio engineering is about trade-offs and making the right ones.
There is no driver, coil, MEMS, or otherwise, which can efficiently and
accurately reproduce the entire range of human hearing at reasonable SPL.

For applications below 200Hz, there really isn't much better choice than a
coil-driven speaker. You are limited to very low frequencies, so the
relatively coarse mechanical nature of the coil speakers is more-or-less
hidden by the fact that any higher frequency harmonics/distortion are designed
out (crossovers, cabinet design, etc).

The best speaker is going to be a combination of various technologies. The
current dream speaker for me would be:

\- large array of plasma or MEMS-based tweeters (2KHz+)

\- large array of 2~3" drivers (120-2000Hz)

\- a handful of 18" drivers (20-120hz)

\- a rotary subwoofer in an infinite baffle (DC-20Hz)

\- DSP/equalizer/time-delay hardware+software for tying the whole thing
together

Also note that the amount of power required to produce the same amount of
perceived acoustic output as you go down in frequency goes up very quickly. 50
watts into a 18" subwoofer is going to sound fairly meek, but pipe that exact
same electrical signal into a titanium dome tweeter and you will develop an
instantaneous case of tinnitus.

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nitrogen
For those like me who hadn't heard of rotary subwoofers:
[https://en.wikipedia.org/wiki/Rotary_woofer](https://en.wikipedia.org/wiki/Rotary_woofer)

I remember reading about a LCR speaker array that was built in the 1970s in
someone's house, with horns that spanned the entire height of the room made
out of cinder blocks. Don't really know how how I would dig that article back
up, but it was a pretty interesting system.

~~~
bob1029
A surprising amount of that content is still out there if you have the
patience to dig for it. AVSForum used to be my primary reason for internet
usage for about 2 years of my life. The DIY community is still extremely
strong (probably stronger than it was a decade ago).

If you have a few weekends, basic electronic & woodworking skills, and a $2000
budget to burn through, you can easily put together a 2.1 channel audio
reproduction solution far more impressive than you could ever hope to buy off
the shelf at any cost. I built a 800 liter subwoofer that plays flat to 13Hz
back in 2008 for ~$600. Still works flawlessly to this day. The key is to be
inventive with materials and design, and to always be aware of the space in
which you will use the equipment. The room is always the most important part
of the audio reproduction equation.

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numpad0
What does MEMS stand for? I mean, isn’t it _Macro_ electromechanical system at
this point? Isn’t that hilarious?

But the response curve of prev-gen looks just fine to me, I wonder if next-gen
Etymotic Research IEM would use a device like this.

