Martin Logan Monolith III Transformer Specs - diyAudio
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Old 20th January 2014, 03:10 AM   #1
diyAudio Member
Join Date: Oct 2013
Location: Nort of Tampa Florida USA
Default Martin Logan Monolith III Transformer Specs

Would you kindly help this poor lost boy to design and build the step up transformer and DC transformer for the Martin Logan Monolith III panels. This needs to be the lowest cost set up. Later I will save up to make a better one.

I will use an active x-over with a high pass of 140Hz so this setup needs to be able to handle that.

The step up ratio needs to be 1:50 and the DC voltage to the diaphragm is 3,200 volts.

1) which transformers should I buy (i.e. what should the X-former specs be).

2) wiring instructions, diagram or schematics

If possible, I'd love to find transformers that ship from the USA such as from Parts Express: the #1 source for audio, video & speaker building components , Mouser Electronics - Electronic Components Distributor , Invalid Request , Online Shopping for Electronics, Apparel, Computers, Books, DVDs & more or any other commonly known place like that.

On a scale of one to ten, my schematic reading ability is about a four point five (4.5)

If y'all can get someone like me through this with success, it would be pretty awesome and I'd have to say that the forums are amazing.

Kindest thanks,

Last edited by Eddiegnz1; 20th January 2014 at 03:13 AM.
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Old 21st January 2014, 02:07 AM   #2
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Join Date: Feb 2008
Location: Jackson,michigan
A good place to start is with CharlieM's interface setup if not get some older used bigger Acoustat interfaces.
I see you have started a new thread on this subject, There is no need to do that.

Jazzman's DIY Electrostatic Loudspeaker Page: The Electronics Package

I don't know what the specs to the Monolith's are or what there designed frequency range is.
With common power toroids you would be okay as long as you stay above a crossover frequency of about 360Hz.

If you need to go lower (down to 40Hz to 80Hz then you would need to either have to use more Toroid's (8 or more) or get a used Acoustat interface as I had already mentioned.
8 cores will get you to the 150Hz to 200Hz range okay with a 1:80 transformation ratio as they are rather large panels.

More info about your panels and exactly what you have to work with would greatly help to figure out exactly what would work, Mainly what is their total capacitance and your intended design setup?
Are you planning a hybrid system using some woofers?


P.S. Do Read up on the latest threads concerning more info on transformer setups.
I have explained many times in great detail as to what and how this things work and their required parameters.
But if there is anything that you don't understand, Please DO feel free to ask, and I or anyone else will gladly help too explain for you in greater detail.
They are a bit of a mystery at First, But they are very simple really once you get to understanding the workings of the Step-up transformer and how it relates to an ESL driver.

Last edited by geraldfryjr; 21st January 2014 at 02:17 AM.
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Old 21st January 2014, 12:21 PM   #3
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Join Date: Oct 2013
Location: Nort of Tampa Florida USA
Below are the specs of the Monolith III from the only need to look at page five since all the specs they provide are there.

The step up ratio needs to be 1:50 not 1:80 (i.e. it will have to be 1:50 no other ratio will be used). The high pass x-over point needs to be 140Hz (no other x-over point will be used ONLY 140Hz).

Thanks so much for your help
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Old 21st January 2014, 01:36 PM   #4
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Location: Jackson,michigan
Then use 8 9V/115 transformers wired for 18v/920v this will get you to 1:51.1 and down to 150Hz at 54Vrms.
I don't think 10hz will make to much of a difference, although it is right at the edge of core saturation.

AN-0209 - 25VA 9V Transformer - AnTek Products Corp

Using 1:80 will up your sensitivity but may drop your impedance quite low considering their size and amount of capacitance they may have.

At $88 a panel isn't to bad but I have seen some complete Acoustat interfaces go for not much more than that.

If you limit your input voltage to 27Vrms you might be able to get away with using only 4 cores per panel wired as 9V/460v.

For 140HZ operation you would have to drop your input voltage to 50.4Vrms and 25.2Vrms respectively.

That would be right at the edge of saturation and should consider another 5% to 10% drop of input voltage in order to not get any saturation if you set your crossover at 140Hz.

The transformers are designed for 50hz operation, so this is the lowest factor you have to work with when calculating your saturation point per voltage input.


P.S I hope that you have a big amp that can swing such a high voltage with only a 1:51.1 ratio.
This would only be 2500Vrms and you would only need 31.25Vrms to get to the level with a 1:80 step-up ratio.
Providing the amp can supply the current.
If you have a capacitance meter you can measure the capacitance of the panel and that would give you an idea as to what your final impedance may be not including the transformers capacitance's.

Last edited by geraldfryjr; 21st January 2014 at 01:42 PM.
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Old 21st January 2014, 02:27 PM   #5
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Join Date: Feb 2008
Location: Jackson,michigan
If you used these 15V transformers this would get you to 1:61.33. and a edge of saturation voltage of 42Vrms at 140Hz for 2575Vrms for the panel.

I don't know what the limits are of what those panels can do, But with a 5Kv bias it should be quite loud at 3641Vpeak (7280Vp-p)!!

AN-0215 - 25VA 15V Transformer - AnTek Products Corp


Last edited by geraldfryjr; 21st January 2014 at 02:34 PM.
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Old 21st January 2014, 04:37 PM   #6
X83 is offline X83  United States
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The ML Monolith-III transformers are just the regular EI-core style that have single primaries with dual secondary's which can be arranged for a 1:50, 1:75 or 1:100 ratio for various models. You can purchase these transformers from ML part number: F9283 which sell for $359.13ea. plus shipping and the wiring schematic for the 1:50 ratio is listed below.
Attached Files
File Type: pdf Martin Logan Monolith 3 L-bracket rev 2.pdf (16.4 KB, 37 views)
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Old 21st January 2014, 06:02 PM   #7
Join Date: Nov 2010
I did make many different esl transformers in the past but i stopped making them. Nobody is interested in a quality transformers, most people are interested in cheap transformers.
For 75,- or less you can not make a good esl-transformer unless 1000 or more people buy. What i have seen so far no "standard" transformer is good enough. Specially for full-range.
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Old 21st January 2014, 11:50 PM   #8
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Location: Nort of Tampa Florida USA
I have recently heard that most of the "standard" transformers result in a decreased frequency response in the high frequencies....something to do with the core material?

What type of core should I look for ... or which specific transformer will NOT compromise the high frequencies that are above 18Khz ?

They recommended the following type of "Audio" transformer.
Standard Range

are there other sources of good "audio" grade transformers that aren't so expensive? Or at least one that is close to being "Audio" grade with minimal compromise in the high highs?

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Old 21st January 2014, 11:56 PM   #9
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Location: toronto
I have 4 Dayton Wright EI core 80,000 ohm secondary ESL step up trans formers - each one weighs 39 lbs - the best -$75 each , but shipping won't be cheap
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Old 22nd January 2014, 04:06 AM   #10
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Location: Jackson,michigan
There you go...Perfect !!!!
And full range too !!!

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