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)
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.
_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.
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
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.
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).
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.
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.
Did you maybe mean transformers? IIRC electrostatics use rather high voltages.
Cone+coil speakers are near-field quasi-static H-field actuators.
They talk about a thin conducting layer on the rubber, quite a different thing.
Well this tells me nothing.
(The two meanings of this word are essentially opposite)
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
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?
