Electrostatic panel excursion

[Bruce Weiland]

I give up.

I have searched online and this forum. I seem to have some trouble finding a definitive answer.

What is the max excursion of a Martin Logan ESL panel? And if you know, more specifically a Prodigy. I am wondering how much air volume the big panel can move?

Is it plus or minus 1 mm? ie. 2 mm of excursion for push/pull? OR more, or less?

Thanks for any response.

Bruce

 

[User211]

Funny I was talking about this the other day with an Apogee refurbisher.

He seems to think about 4mm for a Duetta bass panel which does 25Hz without being down in DB if you catch my drift.

So +/- 2mm for this panel? I'll ask him again to make sure it isn't +/- 4mm.

 

[User211]

As an aside, driving the bass panel with a sig gen at 15 Hz produced quite scary looking excursions - so I stopped pretty quickly.

I think high surface area with relatively low excursion allows ESL and planar magnetic panels to go lower than the excursion would suggest - relative to typical dynamic drivers.

 

[MPS]

I think it mostly depends on the air gap. Diaphragm movement in the bass section of the CLX was clearly visible while playing Hugh Masakela's Stimela from vinyl.

 

[Bruce Weiland]

MPS, yes, but as I understand it the bass panels on the CLS are double specifically to allow greater excursion.

 

[MPS]

CLX does indeed have doubled diaphragm in the bass panels but it has nothing to do with maximum excursion, purpose is to create higher driving force. I'm wondering little bit about your interest in excursion because maximum SPL is equally depending on surface area and power handling capacity, for example higher cross over frequency helps to prevent transformer saturation etc..

 

[Bruce Weiland]

Yes. My interest does have to do with max SPL, and..... dynamic range.

I listen in the extreme near-field, so both are handled for me.

I was wondering what volume of air max excursion could move.

There are many line source dynamic driver systems that say their claim to fame is the small amount of driver excursion used, because they have such a large radiating area. ie Pipedreams by Nearfield Acoustics.

Of course our ESL's have such light weight diaphragms driven over their entire area, other than pure volume of air, advantage ESL. And the larger the panel the more air can be moved, given equal excursion.

I recently auditioned some very cost effective dynamic speakers in my house with my system. While they were very good and a great buy, they could not come close to doing for me what the Prodigy do. Of course the 4.5" flat dynamic driver had a greater excursion than any ESL. But given that is was a single driver I am sure it could not move nearly as much air as the Prodigy panel at all the frequencies it covers,

 

[User211]

When you heard the Prodigy, were you extreme nearfield?

 

[Bruce Weiland]

Yes on the Prodigy. That is the way I have listened to them for the past 6+ years. I just lost my head for a bit and thought there might be something out there with 10 years newer technology than Prodigy, with better sound for less $$$. That certainly has happened for digital, but it does not seem to have for speakers.

I tried the dynamics both ways. Not near field - ok, near field - closer, but no cigar (only the old people know what that means).

This will give you an idea of how "extreme near field" I listen. Please note the chair location in the second system picture.

http://forum.audiogon.com/cgi-bin/fr.pl?vevol&1317958032&view

Bruce

 

[User211]

After my last post, I wondered whether it was you Merry Xmas - I was astonished when I first saw your setup

 

[Bruce Weiland]

Yes 'tis me.

I recently heard the new $46,000.00 Wilson's sound really good. I have never been impressed by any Wilson's at any price prior to this, regardless of what was up stream. Of course they were using the latest ARC reference, and ten's of thousands in wires and stands (probably about $200,000 worth of system). None the less I was impressed. They were primarily playing vocals, both accompanied and acapella, my favorite stuff.

That got me interested in some speakers that sell direct and are supposed to be every bit as good as the Wilson at about 1/13th the price. I ordered and listened for a little over 50 hours. Extremely good for about $2k, and for someone not wanting ESL a no brainer, but not for me.

So, I made some additional changes up stream and was back in ESL heaven again.

The Prodigy have never failed to reveal upstream changes, even subtle PC software changes (not so subtle in my system). Synergistic changes are almost immediately revealed.

So back to the thread.

What is the maximum excursion for Prodigy panels?

I have read that max for ESL's about 80% of the gap (membrane to stator).

What is the membrane to stator gap of a Prodigy or other ML ESL?

 

[Bruce Weiland]

My guestimation, stator to diaphragm 2mm. @ 80%, 3.2mm peak to peak. Any other input?

 

[Rich]

Just checked out your system. Those are some mighty big headphones you got there, Bruce. :rocker:

 

[User211]

My guestimation, stator to diaphragm 2mm. @ 80%, 3.2mm peak to peak. Any other input?

If no one knows, just cut a small thin strips of paper/card of known thickness (might need a micrometer) and shove it in the holes... old style bigger hole stators on a Prodigy - should be doable.

 

[JonFo]

My guestimation, stator to diaphragm 2mm. @ 80%, 3.2mm peak to peak. Any other input?

Hi Bruce, In all my years on this forum, I do not recall a precise number being quoted by anyone from ML regarding the diaphragm movement, if you want to get DIY input on it, a bunch of folks over on the DYI audio forum can talk specifics about their designs and theory.

For Gen1 panels, like the prodigy (and my Monoliths), I'd guess that total P-P displacement is on the order of 2.xmm or there about. The diaphragm is pretty taught and even with significant input (>800w direct-drive, no crossovers or resistors in the path) playing ridiculously loud (>100dB), visibly, the diaphragm barely moves.

Now, when you do the math to figure the total volumetric displacement, even that small xmax yields impressive figures compared to any other driver.

If you want the formulas for that, you'll find them in in this article on ESL theory: http://www.quadesl.org/Hard_Core/ESLTheory/esltheory.html

 

[Tosh]

It had been my assumption that the 3M brand double-sided foam tape that ML originally used as spacers is 0.063 inch (1.6mm) thick...

 

[Bruce Weiland]

Rich they are. And they are wonderful.

 

[Bruce Weiland]

Justin,

I did something like that. Smoothed if the end of a round tooth pick and gently inserted it and "eye-balled", then measured. That is where I came up with 2mm. But that is probably wrong. It is probably 1.6 mentioned later in this thread.

 

[Bruce Weiland]

Jonathan, thanks for the reply. I'll bet you are correct.

 

[Bruce Weiland]

Tosh,

That makes sense to me.

Bruce