Classic components could be replaced by rubber in next-gen loudspeakers | Hacker News Reader

Classic components could be replaced by rubber in next-gen loudspeakers

polytechnique-insights.com

129 pointscrousto82 comments

These speakers seem to work like this:

There is a rubber layer, coated with conducting material to serve as electrodes. The signal is applied in form of a high voltage which makes the electrodes attract each other and contract the rubber in between perpendicular to the surface (i.e. the rubber layer gets thinner). Since the rubber material is relatively incompressible though (volume of the material doesn't change), the surface area of the membrane has to increase in return. To generate sound from that, the membrane is stretched over a cavity that is under higher than ambient pressure which helps expand the 'balloon' when its surface area increases. This displaces surrounding air which means the contraption is emitting soundwaves.

(I could only find a thumbnail of the first page of a paper from that professor and extracted this from it)

https://www.aes.org/e-lib/browse.cfm?elib=21108

This sounds like an "electroactive polymer." there are some squishy tapes made by 3m that incidentally have this property out of the box. Make a spot of conductive carbon paint on each side, apply a few kV, and watch the spots double in area as the electrostatic forces squish the material.

The article mentiones "conductive grease" that is added to the membrane.

It sounds a little like Bayer’s ViviTouch, but for higher frequency bands. ViviTouch was only used for haptics and sunwoofers as far as I know. https://www.innovationworldcup.com/finalist/vivitouch-eap-he...

Other than the vacuum bit, it sounds a lot like planar headphones.

> Current loudspeakers use a magnet coupled with the movement of a copper coil to vibrate a membrane. In the future these heavy, bulky, and expensive components could be replaced by a dielectric elastomer membrane.

They mention efficiency, but not power. I don't like how this is framed as the general future of all speakers when it's really just the future of midrange drivers.

Heavy speakers is a plus when moving low frequencies. Otherwise you have to strap or bolt them down and together.

_Might_ be the future of mids, but I doubt it. Advancement in ribbon speakers is more likely IMHO. Also people develop a taste for how some speakers sound. I don't see guitar music being played on anything too different for a while, unless it has the same sound character. Even if technically it's a better reproduction, it has to reproduce how paper cone speakers sound now better than paper does. Seems unlikely. To win, people have to like the new sound more, or not be able to tell the difference.

Considering how many people listen to music through phone speakers or laptop speakers or portable mono speakers I think consumer tolerance is far higher than you're guessing. Many homes these days don't have any speakers aside from the ones that came with the TV and if you want higher quality you reach for the earbuds or headphones. The vast majority of people aren't audiophiles.

There are cheaper and lower co2 footprint ballasts than copper and magnets for getting the weight.

> Heavy speakers is a plus when moving low frequencies. Otherwise you have to strap or bolt them down and together.

I get it.

But I would rather have that in two parts. It is not always needed, in that there is a place to put the speakers, and I could leave the heavy stuff at home

While that's true, there are niches that have different requirements.

One that springs to mind (for me) is audio monitors, where speakers are supposed to (in theory) be neutral in order to provide a good reference.

Wouldn't rubber dry out over time? If you pay for a good set of speakers you probably want them to last for decades.

I have a pair of 35 year old Mission speakers constructed using rubber and so far there's no evidence of degradation and they still sound great.

I imagine if this was a tyre then it wouldn't fare so well because the rubber compound is for a completely different use and also exposed to adversities such as wide temperature differences and all sorts of kinetics that a speaker will never experience (hopefully).

Lots of traditional speakers already use a rubber ring around the edge of the cone.

Which is what turned to dust in my twenty year old infinitys. They were the cheaper ones but still surprised me.

Same with my Bose. The foam surrounds were short lived. Rubber lasted longer but was not as widely used.

The foam surrounds can be replaced. It isn't difficult and you can buy kits for a lot of different sizes including the glue.

One thing to watch is to ensure the cone is still centred but anybody who is patient can fix a bad foam surround.

I've done it! A relative of mine had two Gallien-Krueger 250ML guitar amplifiers, which are an interesting bit of kit, but the 5" speakers had foam surrounds that rotted out. I ordered and installed generic replacements from Parts Express. For my part, I was just curious about how the amps would sound.

As for the Bose, they were nothing special as speakers, and I already had a stereo that I was happy with, so I disposed of them.

Yeah, foam surrounds are the cheapo stuff, neoprene lasts.

They should use whatever bike innertubes are made out of. I've used innertubes as bungees outdoors, and they're quite durable.

I bought (separately, used) a full set of older Infinity surround speakers. Eventually they all had to be re-foamed, but I managed to do it myself with parts ordered online. Have some acetone on hand to take the glue back off if you get it wrong and have to try again...

This was about 10 years ago but here in New Zealand I found someone who could repair and replace the rubber so my 30 year old infinities are as good as new.

Couldn't you just replace it? We also pay for good cars, but we still change their tires every so often...

Speaker surrounds are replaced when necessary. For several decades foam was used, and it tended to break down. The butyl rubber usually used now lasts thirty to fifty years when not exposed directly to sunlight.

Why would I want to replace the headphones I am using for a decade with something I have to replace every few years. Its already sad enough that I have to replace my phone every year or two because of its battery and software upgrades that slow it down.

You can now add headphones to your upgrade cycles because number of new phones with reasonable specs and wired headphone support are becoming rare.

If this proves cost effective to manufacture and resulting headphones come with inbuilt obsolescence due to batteries and degrading rubber, we'll see manufacturers aggressively pushing this new technology.

Well I guess it's not the wooden box of a speaker that costs $2000-$30000 (normal price range for consumer Hi-Fi speakers). Replacing the speaker drivers would be more like replacing everything within the body of a car.

How do hifi speaker vendors justify such ridiculous prices when most studio monitors are way better priced than that? Insane.

Justification isn't really a thing in that market (see also: luxury watches).

My friends who are into hi-fi/audiophile stuff who value accuracy typically do go for studio monitors or similar (e.g. Harbeth) vs. stuff like Wilson Audio. Some of them still buy fairly woo-woo stuff like spendy cables even though they might know better, but at least they don't go in for the pure scam stuff like Shakti Stones or directional Ethernet cables...

Not at all. Pro grade reference monitors can cost a small fortune. PMC BB6 XBD-A for example are $125,000 a pair.

I genuinely wonder the same actually. Seems like there would go even more engineering into making a speaker that is "true" and not coloring the sound as one expects from their monitors.

There's plenty of real engineering but it's only engineers that can differentiate the heavily marketed and absurdly marked up snake oil things from what's real. DIY people share honestly good designs that are underperformed by speakers/amps that cost 10x or more.

For one, studio monitors are typically near-field speakers.

"near field speaker" is a marketing term that has no meaning.

thats not true. A near-field speaker tends to be a speaker that performs well at closer distances. its obviously implied given its prefix.

https://en.m.wikipedia.org/wiki/Studio_monitor

You dont know what you are talking about. “has no meaning” is such a nothing sandwich,

Near field is a property of the space, not the speaker. Would suggest reading https://digistar.cl/Forum/viewtopic.php?t=547

You're right that it's about a space, or a field, which is in the name, but you're wrong in contradicting the other poster. The near field is determined by the radiating surface, the front baffle of the speaker. Room height line arrays for example have a large near field. Near field speakers are those with tuning designed to be flattest when listened to inside the near field. The link you posted is confused and misleading, which is unfortunate since they dressed it up as some kind of "myth busting".

It's easy to trick people into overspending on audio gear because you can use their love for music and their subjective biases and their egos against them. It's like the perfect situation for slimy sales tactics.

Beware, if you're spending $10k+ on consumer hifi speakers you're almost definitely getting ripped off.

It costs only a few thousand at most to get the raw parts and materials to build truly world class speakers (quality-wise) that are loud enough for any normal living space. Maybe not for a concert hall type space, but that's not consumer hifi anymore.

I find it a bit strange that this article doesn’t mention electrostatic speakers, as the two appear similar.

It would also be worth mentioning if this new tech suffers from the same limitation as electrostatics, namely that the membrane’s range of motion is so small that you need several square meters of membrane to reproduce low frequencies at high volume.

This appears to be describing an electrostatic speaker. They're on the market, and have been for decades, using mylar or a similar material.

It doesn't. This scheme uses a membrane like the electrostatic speakers, but otherwise it is quite different. In the electrostatic speakers, you load the membrane with extra electrons and then use electro-magnets to apply a varying electric field across the membrane in accordance with your sound signal. Since the membrane has much more electrons than protons, the electric field causes the membrane to move. This method requires magnets.

The system in the article does not use magnets. What they do is they make a membrane that moves when a voltage is applied between its top and bottom surfaces. Thus, the membrane can probably be referred to as being piezoelectric, although the article does not use that term. In this case you can apply the sound signal directly to the membrane and make it move, and when it moves it creates sound. Thus, this system does not require any magnets.

The lack of magnets will make it much lighter. Also, the fact that you are applying the signal directly to the thing making the sound may result in better sound quality.

Electrostatics shouldn't need magnets. The very name implies that; magnets have no appreciable effect on static charges.

Did you maybe mean transformers? IIRC electrostatics use rather high voltages.

You are correct. They do not use magnets but grids of stators. These grids of stators apply a good old fashioned electric field not a magnetic field. But the main difference remains, you still need two latge heavy things that take the sound signal and actually move the membrane.

There are no magnets in an electrostatic speaker. They are near-field quasi-static E-field actuators.

Cone+coil speakers are near-field quasi-static H-field actuators.

I'm not so sure. Electrostatic speakers have big heavy metal electrodes.

They talk about a thin conducting layer on the rubber, quite a different thing.

They definitely look very different. I understand how ESLs work, but I don’t quite get how these move. Can anyone explain?

Like an electrostatic speaker the opposite charges' attraction generate movement. The difference is in an ESL one of the charges are stationary. In this new scheme, both charges are on the membrane but on opposite sides where attraction compresses/thins the rubber causing it to expand along its planar directions causing the dome to get larger. The inner air pressure is to assist the expansion movement.

As I understand it, the rubber being is forced into the shape of a dome via air pressure, which makes one side a bit bigger than the other. The electrostatic charge on the opposing faces when one is bigger than the other would cause it to flex - acting as a speaker diaphragm.

It's a bit of a guess though; its definitely outside my wheelhouse.

Magnepan speakers have been around since the 1970s. They do not have anything heavy. Martin Logan speakers do have a heavy base presumably the driver.

Don't confuse magneplanar speakers with electrostatic speakers. Other than them both being flat they are quite different beasts.

Yeah I am really nonplussed how this is the top post on HN right now (I know that is against the rules to mention but really)

This is the response of someone who knows that electrostatic speakers are a thing and has seen marketing or other images of them, but has no idea how they work and lacks either the curiosity or the capability to learn. The speakers described in this article are nothing close to electrostatic speakers.

Because it has nothing to do with EL speakers -- this is just the casual HN dismissal

I must have misread, but it seemed similar to me and would love an explanation?

They rather seem to be electrostriction speakers.

> Yeah I am really nonplussed

Well this tells me nothing.

(The two meanings of this word are essentially opposite)

I can't tell if serious or sarcastic. Either way, here you go.

nonplussed : adjective

- Bewildered; unsure how to respond or act.

- Unfazed, unaffected, or unimpressed.

- filled with bewilderment

This meets the criteria of Poe's law. It is equally reasonable to assume _you_ are being sarcastic or serious. If they didn't just recently look up the definition themselves, they wouldn't have commented about the conflict in the two definitions.

The wrong meaning is the opposite of the right meaning

Summarizing dictionary.com:

1. Surprised and confused 2. Unperturbed

"Yeah I am really unperturbed" doesn't make sense in context of it's parent.

I'm not sure how you could be nonplussed about this.

>"Yeah I am really unperturbed" doesn't make sense in context of it's parent

It's not just unpertrubed, it's also "not impressed".

In the context of the comment it basically means "I see this speaker announcement as nothing special, what's the big deal?".

The commenter specifically used the word nonplussed in reference to the ranking of this post on the front page. The fact that their surprise and confusion stems from the promotion of unimpressive stories does not change the meaning from surprised and confused to unimpressed.

>Well this tells me nothing.

Well its certainaly not a non negative statement because its talking about being plussed, which is a positive statement, so a nonplussed person is truly chaotic-neutral.

I was wondering much the same, except I note that my pal’s massive Quads and the older radiator-like versions at uni were still crazy heavy due to the power supply (I assume) and they were a bit short on warm bass, perhaps these “new” speakers run on a trickle of power and produce bass like a Cerwin-Vega for all I know?

The power supply problem is not power but voltage, electrostatic speakers just require high voltage

Also they are expensive audiophile thing so good chance they were driven off some super inefficient and/or made on discrete componentes, hence the size

My screen readers reads that site in a verry strange way. It says that there is soft hyfens in a lot of the words so it reads the words like reproduce as"repro duce"

It looks like they are doing some sort of dynamic text justification. If I change the text width by resizing the window it dynamically inserts hyphens at line breaks. Presumably via some javascript library.

Ehhhh interesting, might go well for tweeters. Can't see it being great for bass. Can't be arranged in a paraflex horn config.

The article mentions the fragility, but seems extremely optimistic on the ability to solve this, but I'm not sure way. It just says "once this is overcome" but the things it seems to be talking about are major barriers to a commercial product.

It was just the other day I was thinking how big, comparatively speaking the speaker components are in MacBook and iPhone. And if we could somehow make it even smaller without any compromise on quality and longevity.

This seems only mildly different than already existing electrostatic drivers??? In terms of getting rid of heavy magnets at least.

Yes, as we know from the history of electrostatic speakers, all you need to replace those bulky magnets is a sheet of mylar the size of a billboard, and also a regular magnetic voice coil for the half of the power spectrum that they can't handle.

These seen smaller than a billboard: https://www.crutchfield.com/S-Me16Db11xTX/p_839EMESLD/Martin...

And with lower frequency sound, aren't heavy drivers actually better? You literally need more mass/energy to push more air, but at a lot lower frequency so the effect of moving the mass back and forth at 20Hz does not really matter as much as 40Khz?

The weight of the driver is not really a factor so much as a side effect of the engineering. You want to look at it in terms of total volume displaced and the sensitivity (if you are thinking about efficiency). Drivers with more surface area & excursion typically do have larger magnets and support structures.

LFE reproduction is all about moving large volumes of air by any means necessary. There are relatively featherweight subwoofers that literally use fans to move volumes of air and achieve performance that is impossible in traditional drivers of any weight class.

Doesn't really matter how you do it as long as things stay in phase.

> There are relatively featherweight subwoofers that literally use fans to move volumes of air and achieve performance that is impossible in traditional drivers of any weight class.

Wow I've never heard of this, what are these called? Would love to read more about this tech

https://en.wikipedia.org/wiki/Rotary_woofer

> These seen smaller than a billboard: https://www.crutchfield.com/S-Me16Db11xTX/p_839EMESLD/Martin...

Right... because this one contains a normal magnetic woofer

If you want an affordable, good sounding speaker that you can build yourself, you might wanna take a look at Tech Ingredients:

https://www.youtube.com/watch?v=CKIye4RZ-5k

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