Inverted ESL

[taichiguy]

I'm intrigued by the "inverted" esl's from FinalSound which, unlike typical esl's, applies the bias charge to the stators and feeds the audio signal to the diaphram. Their website says there is a sealed conductor inside the diaphram (as opposed to a surface coating?)--- so now I'm wondering; how did they do that?

Would the diaphram need to be less resistive in this case, since it takes the audio signal rather than a steady bias charge?

The design's impedence is said to be at least 3 ohms across the entire frequency spectrum (more amp friendly) and is implied to be inherently safer.

I hope that someone here more knowledgeable than myself (that would be most of you) will check this out (link below) and share your thoughts on it.

http://finalsound.com/

taichiguy
(charlie)

[SY]

The clue is their stated thickness for the diaphragm- 12u, about double the usual 6u thickness. It would appear that this is formed from laminating two films together, conductive side in. I haven't searched for their patent app yet, but I'll wager that this is the "secret."

What the actual advantage of this is, as opposed to the claims of the blitheringly stupid ad copy, is quite unclear other than, "it's different."

I would love to see the withering paragraph in Augsperger's JAES patent column. And to meet the marketing guy who came up with the rather ominous "Final Solution" slogan.

[Bazukaz]

Hi,
I am not a big expert , but i didn't like their advertisements.Stating that ESL directivity is an advantage ... More than strange.
Also , i don't understand how they overcome charge migration by this technology ...

[SY]

OK, I've found their US application and it's not as off-putting as the ad copy. But I'm scratching my head to try to see what's really new.

[Calvin]

Hi Sy,

could You share the number of the application with us please? :-)

jauuu
Calvin

[SY]

US 20050147265

Inventor: Maarten Smits

[Capaciti]

Hi,

there is a problem inherently to the inverter technology. Since the membran and the stators are very conductive, the ESL do not work in constant charge but constant voltage mode.

As a result the charge on the membrane will change when it comes near to one stator. As we all know this means non-linear movement and increasing distortions. Especially at lower frequencies the change of charge and the distortions will increase.

This technology has its advantage regarding safety and should deliver more sound pressure at lower frequencies at given audio input voltage. But as always, nothing is for free. Distortions are the limit for such a system.

regards,capaciti

[Brian Beck]

I read the application, which appears to contain several little gaffes. I agree with Capaciti; this design does not appear to use constant charge operation. Furthermore, there is a claim of safety since high voltage AC is removed from the stator. But this design uses +/-3000VDC on the stators. The inventors placed a 10M resistor in series with each DC supply followed by a shunt 4nF cap to ground. While I doubt that the energy stored in these caps could injure or kill, I wouldn't want to touch a stator with my hand while another part of me is grounded. I doubt UL would approve.

Also, I think the use of concave inner stator surfaces is questionable on several grounds.

[TimA]

Perhaps we can assume that the membrane does indeed have a necessarily low resistance but I am not sure that we can assume that the stators do too.....unless I have missed something.

Tim.

[Bazukaz]

Originally posted by Capaciti
Hi,

As a result the charge on the membrane will change when it comes near to one stator. As we all know this means non-linear movement and increasing distortions. Especially at lower frequencies the change of charge and the distortions will increase.


regards,capaciti

Hi,
If we would make a membrane resistance constant and low , and allow some current to flow through it , like in a conductor , wouldn't this decrese charge migration ?

Regards,
Lukas.