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Geting better output of the ESL panel
Geting better output of the ESL panel
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Old 29th December 2011, 08:53 AM   #1
tyu is offline tyu  United States
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Join Date: Jul 2009
Default Geting better output of the ESL panel

I have been working on some 16"x48" panels....thay are crossover at 200h up to 20k....After haveing the Tranfourmer set up like most.....with the centertap grounded an one end of the winding going to the front an the other end of the winding going to the back of the panels..I found that when driven hard the panels would buzz...at frist i thought that this was just the wood i had the panels in....So i put in a diff. Tranfourmer panel set up...
You can see that with this setup the the whole Transfourmers winding is now used to drive the front of the panel only.....So you see the centap is out...Well there is No ESL panels that i can find that have Bias coting on the back side of the mylar...So driving the panel in the nom. way with the centap grounded the one end of the winding on the back has to work harder than the front winding....this makes the Tranfourmers pull harder an harder till it was buzzing... an made the panel buzz....Now this is not the frist time i have used this an have found this in other ESL speakers....so this is a time tested setup...I have put this set in Soundlab,Acoustats,Martinlogans...This is the frist time that with this setup i could hear how it helps the tranfourmer with over load....So what other Good thing dose this do....It give about 2-3db more output....an it takes the stress out of the transfourmers an thay can play louder...An it sounds vary good.....
For give my art...

Has anyone done this setup?
Thanks for any feedback
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File Type: jpg panel se drive 008.JPG (603.4 KB, 474 views)
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Old 1st January 2012, 02:53 AM   #2
beun is offline beun  United States
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I fail to see what difference this would make, the total peak to peak voltage across the stators is unchanged.
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Old 1st January 2012, 08:31 AM   #3
geraldfryjr is offline geraldfryjr  United States
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Yes, I tried that configuration before and I didn't notice in difference in the output or sound quality.
Although it probably makes know difference when the winding resistance is quite low,I still choose to keep things even and symetrical by using the center tapped version.

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Old 1st January 2012, 12:33 PM   #4
tyu is offline tyu  United States
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so you say

I still choose to keep things even and symetrical by using the center tapped version.

I think that the deal.....there not symetrical...maybe on paper...Or if you wind your own tranfourmer... or can spend the big $$$....but with all the ESL transfourmers i have there is a diff. in one winding An the other winding from the centap... an i well say most tranfourmers have this diff.
I have two panels that Arc.....One pops eze,little input...the other has to be push hard.
I am finding with this tranfourmer setup.....the center tap out...the one that pop all the time now has to be pushed harder....an the other stop Arcing...There arc is in the front of these panels .....This tell me that this diff. in the tranfourmer windings must have some thing to do with this....But as with all the mods i do.....you can go back...an see if the sounds better to you...it give better sound when in a two way ESL....the bass driver an the esl panel match better..with this littel more output of the panel...To me it sound like a SE tube amp....or like one of pass SE fet amps...
But this is just one mans O-pine ....newyeardiy,er
thanks for any input...
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Old 11th January 2012, 10:34 PM   #5
tyu is offline tyu  United States
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Default SE info from others...

JonFo....he talk about....His SE setup.Just like the Art i have posted....

After that, it’s basically a stock ML ESL circuit topology. The Signal positive goes to the red lead on the step-up transformer, the signal negative goes to the black lead.
The transformer outputs the positive signal on the gray wire, which in turn routes straight to the rear Stator of the ESL (since the factory passive 2 nd order x-over inverts phase).
The Orange output of the transformer goes to the high-voltage board to provide a reference signal for the Diaphragm and to supply the negative Signal for the Front Stator via the Blue line on BB4.
Additionally, a reference signal ground is fed to the BB4 on the High-voltage board and another is fed straight to the front stator via the second blue lead.

So we no this can be done but think about it..........any one would put the amps neg. on the ACv
leg of the bias tranfourmer....only if the earth grond was also put in so it would be at 0 but no earth is in.....So the amp would see...300vAC....i dont think wount that noise... if he would have look at the bottem of the board he would have seen that only the neg from the amp is in the mix...Or he had a diff setup than i have had in the SL3s i have had...not

Most set are in pushpull
Double check the high voltage wiring. The ML's I've seen have the transformer outputs going to both stators, and the bias high voltage between the transformer output center tap (that you haven't shown) and the diaphragm film. That way the transformer signal drives one stator negative, the other stator positive, and vice versa for the other half of the waveform, for a push-pull effect on the diaphragm.


You are correct that some models have the step-up wired as you describe. There are schematics floating about that depict the orange tap feeding the front stator and the gray wire feeding the rear, with a center tap feeding the high voltage board.

I have pointed this out over an over.....Mr power told me that it was some thing ML had to do to ship there speakers to the UK....

However, the SL3 units I have are wired as I described. I didn't even disconnect the stock wires from the High-Voltage board, xformer nor the connector.
On my xformer, all other taps are wrapped down and unused as you can see in the pic. So no center output tap was ever used.

{This had me scratching my head for a while, but given that it’s the stock wiring (and I have pics of ‘before’ to double-check, plus the other SL3 unit, I feel comfortable this is correct.}
It looks like ML had a design change in the HV board at some point as my boards are from Feb of ’98.
So anyone reading this and planning a mod to their ESL drives should take this into consideration, as there are various modes of wiring these things depending on which rev of the HV board you have.

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File Type: jpg sl3xc%20crossoverdiagram[1].jpg (56.2 KB, 354 views)
File Type: jpg sl3xc_esldrivejpg1[1].jpg (104.8 KB, 347 views)
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File Type: pdf sl3+passive+crossover[2].pdf (8.7 KB, 15 views)
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Old 11th January 2012, 10:52 PM   #6
tyu is offline tyu  United States
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I wasn't disagreeing with your posts about ML moving the ground reference from the center tap to the front stator.

I was only trying to determine how they connected the bias supply since I could not figure it out from your comments or diagrahm in post#19

The bias dose not have be used in the stepup transfourmer.It can be free standing...if it is you can see it can sound better...right...This is a big deal an if it were not i would not be posting it...I am driving a pr of BIG ML Prodigy esl with a 50watt tube amp an get vary good output ....this can not be done with the pushpull setup...you lose output by 2-3db.

An if you have been doing this for 20 years you no any thing in the Audio chan can kill the sound...an yes i would like yours an others help to even get better sound out of the esl...Ml did what thay did... but this is what i am doing to get better sound.

thanks for your time an any info you can give by anyone?

Last edited by tyu; 11th January 2012 at 10:59 PM.
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Old 20th January 2012, 02:02 AM   #7
bolserst is offline bolserst  United States
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Originally Posted by tyu View Post
The bias dose not have be used in the stepup transfourmer.It can be free standing...if it is you can see it can sound better...
Hello tyu,

Sorry for the late reply, I didn't realize you had posted a response here until today.

I agree that ideally for best sound you would apply a charge to the diaphragm and then remove all bias supply connections. But, all panels have some leakage, so the bias supply has to stay connected to keep the diaphragm charged up to the proper level.

The diaphragm can only be charged if one terminal of the bias supply is connected to the diaphragm, and the other terminal to the stators. The usual method is (+) bias connected to diaphragm, and (-) bias connected to center tap of step-up transformer which feeds it to both stators.

But, in the SL3 you pointed out that the step-up transformer has no center tap.
So, where did Martin logan connect the (-) bias supply? I didn't know until I saw your diagrams.
They hooked it directly to the front stator.
The rear stator is also connected to the (-) bias supply through the step-up transformer secondary winding.

Combining the power supply schematic and panel connection diagram you had previously posted, I highlighted the bias supply connections.
(+) bias supply connection to diaphragm is shown in Red
(-) bias supply connection to front stator and step-up transformer is shown in Green
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File Type: gif HV_connections.gif (113.0 KB, 325 views)
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Old 20th January 2012, 12:33 PM   #8
tyu is offline tyu  United States
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You must think you are the ONLY one who has done any work on ESL ...the people here may buy this but i dont ....goodluck

Pass on my Post...thanks
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Old 21st January 2012, 03:59 AM   #9
Few is offline Few  United States
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Tyu: I'm a latecomer to this thread but can't find anything in it that warrants your most recent response to someone trying to help you, especially when they have done it in such a polite manner.
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Old 21st January 2012, 06:25 AM   #10
Paul S is offline Paul S  United Kingdom
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Mmm, Agreed, perhaps you could explain tyu?
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