See-Through, Paper-Thin Speakers

Cormac writes "Here's an interesting article about scienists in the Korean Institute of Science and Technology (KIST) who are developing see-through flat speakers which (they claim) could be rolled/folded up and put in your pocket or even be pinned to a wall." I wonder about the fidelity, but there could be some excellent potential here: it irritates me that my center channel is on my TV. Without getting a projector and putting the speaker behind a screen, something like this could just be built onto your TV. But can it sound good?

Comments

Re:Like electrostats...

[Chris Johnson]

Maggies aren't electrostatic. They're driven by a linear voice coil along the surface of the stretched mylar. There's also Sumo Aria/Museatex Melior, which are _center_ driven mylar: normal voice coil, no speaker cone, and the coil attaches to the mylar which remains flexible (unlike electrostatics, the film doesn't move in a planar way- it moves through ripples from the driving point)

I've experimented with these fairly extensively, and still am from time to time. DIYing center-driven stretched-mylar speakers is fun, but tricky to make useful. Here's what I learned:

• Resonance is not your friend. All these speakers have to control resonances somehow, and it's a tricky problem. Resonant notes will fart and honk, usually in the bass, and blatantly ruin the sound.
• They're incredibly wide-range at _any_ size, but the max output volume is size-dependent and very limited. This type of speaker just doesn't want to go loud, but even small ones will try real hard to put out strong bass. Quite weird really. This is, I think, specific to the point-driven or line-driven ones, not electrostatics or piezos.
• Dispersion is stunning, and contributes to the sense of not-loudness. You can stick your ear in one and it's very subdued volume. Then you go to the other side of the room and there's no falloff in volume. It's the ultimate 'mellow party' speaker in that there's no place that gets 'blasted' by the speaker, not even right in front of it.
• Dispersion is amazingly wide-range. The highs are very extended, even far off-axis.
• If you make cones extending out from the speaker voice coils to the mylar, in theory you'll have a super-point-source but in practice it only makes the lack of volume even worse. I've got some half-built experimental drivers sitting here which have some improvements- the magnets were encased in a 2-liter bottle filled with concrete making the unit real heavy, and the voice coils have Ping-Pong balls (with a hole in the back) where the dust cap would be. This sphere shape transmits stresses well, and has a larger contact point.

DIY is fun :)

Air Pressure

[Lally Singh]

If you put them on a screen, LCD or otherwise, wouldn't you have a vacuum of air pulling the speaker back? That seems like it would create a lot of distortion. Also, even if that part was fixed, wouldn't the sound itself cause distortion on an LCD screen? When I lightly touch my LCDs, they change colors in that area. Imagine a speaker as big as the screen in close contact with an LCD screen playing your matrix dvd...

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Re:the problem with bass reproduction...

[svirre]

To reproduce low frequencies the speaker surface must move a fairly large distance. The problem is that this movement actual creates a doppler shift in the high frequencies, creating a "muddy" sound.

While this is essentialy true, it isn't the most significant problem with large panel speakers. These are large enough that the surface won't have to move much. (of cource if you make them small you're screwed).

Panel speakers traditionally got two problems:

They tend to be dipoles which means the got to be huge or have no bass. Once the path from the rear of the driver to the front becomes small compared to the acoustic wavelenght it exhibits an acoustic short which works to cancel and phaseshift LF sounds.

Also any driver which active surface is larger than the wavelenght of the sounds it reproduce will exhibit beaming and comb filtering since for a given point in space the path to two different points on the driver will be different. For large drivers the difference can become significant compared to wavelenghts and interference ensues.

Some panel speaker technologies also suffer from beeing very hard on the amps (el-stat).

In short it's hard to justify making a panel speaker.

Remember that it is a panel doesen't make it thin unto itself. If you don't want a dipole you still need the box, and if it is a dipole the problems above occurs and it will still have to stand out from the wall to avoid interference from back wall reflections.

I don't think these are for Audiophiles...

[Ted V]

Anyone remember the disposable Paper phones currently in design? We never thought those would replace cell phones (or heaven forbid, one of those option loaded corporate receptionist phones). But it's still a good idea because you can spend a few bucks on a paper phone if you need to make a call, and just throw it away when the time runs out.

Same thing here with paper speakers. This isn't designed for watching The Matrix or Gladiator in all its glory. These speakers are better suited for cheap things when you just want any sound production whatsoever... Like talking advertisements in magazines...

On second thought maybe this isn't a good idea. :)

-Ted

Impressive Possibilities

[vergil]

The possibilities for paper-thin are endless (depending, of course, on cost). Imagine:

- Ever been to a large protest or demonstration? Groups with axes to grind are typically under-funded, and habitually rely on tinny Radio Shack megaphones to "get the word out" - a marginal improvement over shouting, given ambient street noise. With these speakers, a dissident group could easily seed a crowd with plastic amplifiers taped to their ubiquitous posterboard placards.

- Pack a stack of these piezo-electronic sheets in your backpack, find an abandoned warehouse and a tube of super-glue and voila! Instant rave!

- Promotional companies that currently wheat-paste metropolitan walls with repetitous movie/concert fliers might find a way to paint their advertisements on sheets of the aforementioned plastic film with a flat EEPROM backing, thereby augementing their garish displays with short bursts of sound. Wait, I should patent that idea.

Sincerly,

Vergil
Cluebot.
Vergil Bushnell

Here's your problem...

[b0r1s]

The problem with these existing speakers, critics say, is that while they do a good job of reproducing high-frequency sounds, they often are not substantial enough to produce deep bass sounds, or play at high volume.

"Even with quite large ones, which I've got a pair of them in my living room, they need a bass reinforcement," says David Pearce, a research fellow in functional materials at the University of Birmingham in England who specializes in piezoelectric ceramics. "Hearing these sort of panel speakers individually, they always sound kind of tinny. But then you put them together with bass support and you say, 'That sounds pretty good, actually.'"

Well, it was nice until that part... No volume and no loud bass, I'll stick with what I have, thanks.

Plastic? I wanna make music with FIRE!

[dbowden]

I don't think these are all that new - there have been flat panel speakers around for years. The only thing I see diffrent about these is that they don't require the supporting framework that the current ones require.

For something really cool, sometimes you have to look at older technology, like the plasma speakers described here.

The idea is that the shape/size of a flame can be influenced by a high voltage signal, and the resulting changes in the flame are broadcast as a high fidelity sound. Here's a quote from the above site

"It is really simple. It is a modulated RF power amp with a controlled ionic discharge. By modulating the oscillator with the audio signal the flame size changed and so the air pressure changed also . You hear the sound directly through the air without modulating a diaphragm. So there are no moving parts, no distortion and none of the problems other tweeters have."

There's not much bass to these, but boy are they cool looking!

And, as an added bonus, you get to play with nifty Tesla coil technology.

These are true Geek Speakers.

great.

[sllort]

you mean you can make clothes that act as a loudspeaker
riding the subway is hard enough already!!

that said, think of the applications for screwing with people if you could make your sweater talk... or a window... or a mirror.... oh my.

sorry, need to go make devilish plans...