Custom ESL using quest panels

[Brandon Hartwick]

@Leporello I just went with these transformers because they seemed like the best shot I had with the information I had to work with.

I'm not entirely sure of what I'm doing here, but it seems to be working.

 

[ESLFan]

The problem I see with using a power transformer as an audio transformer is the non-flat frequency response. Secondly the proper core material in an audio transformer is M6 steel which contains some silicon to increase permeability. In addition nickel is added to increase the permeability further and reduce the hysteresis. higher permeability means less windings required for coupling. Less windings means lower resistance and lower power loss, Bad hysteresis creates distortion. A typical audio transformer for a tube amp will have distortion below .1%. I have never measured a power transformer at high frequencies. But if harmonic distortion is bad so will be the inter-modulation distortion and the sound will be harsh. Maybe the core material in toroidal transformer is more ideal, I have no experience with that. But I do know that toroidal cores saturate more easily, so if there is any offset on the output of the power amp, and also because of the lower winding resistance, as fairly large current could flow decreasing the ability for high output. I am assuming with big panels you want pretty big output?
I would really be interested if someone had run some distortion numbers using a power transformer as a step-up. If transformers were so easy, then people would not spend a fortune on moving coil step-up transformers. I know its low signal level and needs tons of shielding, but low distortion is a primary driver there.
Of course for the adventurous, you buy an EI core and wind your own. The secondary can be very thin wire, since the electrostatic panels don't load the transformer much and impedance is very high.
I had a set of Accustats at one time. They used a transformer with a higher ratio to get the bass boost and crossed it over in the bass region. Worked very well.

 

[Jazzman53]

Hearing is believing.

I wouldn't recommend my cheap toroid setup for driving full range ESLs, but I can attest from experience that a tandem pair of single-primary 50VA 230V/6V toroidal power transformers (75:1) works quite well driving hybrid ESLs operating above 200Hz, and the sound quality is excellent.

Around 2009, I was inspired by a much-respected ESL builder on the DIY Audio Forum to tryout the tandem single-primary toroidal power transformer setup. I liked them so much that I started using them in all of my ESL builds.

I originally used the tandem toroids to drive 4ft2 perf-metal panels, and later (2015) to drive my newer segmented wire-stator panels.

For years I've fed these cheap power toroids with ridiculous power from multi-hundred watt RMS amps, and I've never smoked one. Their cost vs performance is just icing on the cake and makes building ESLs accessible for more people.

Linked below are a couple of posts from "Calvin" on the DIY Audio Forum. The second post includes response plots comparing the inexpensive power toroids to the excellent ESL-specific Aplimo transformers.

Enjoy!
Charlie

Power toroids for ESLs

Comparison to Aplimo ESL Transformer

 

[ESLFan]

Very interesting link. I did come to the same conclusions that an ESL transformer is different from a tube output transformer. It could be true that the frequency response is quite close between the two. So far I have not seen any distortion figures for each one. Dayton Write claims 0.1% distortion for their speakers and he claims it is all caused by the transformer. I had a read of your webpage, quite impressive. I like the idea of a segmented panel. After all these years, I never build one, though I also read the Sanders book. Here is a plot of the Dayton Wright speaker with transformer. No fancy computer plot here. This was done in 1977, so yes I have been at it for many decades. The two plots represent a 100:1 and a 50:1 turns ratio. The reason why the plot does not drop below 3 ohms is because there is a series 3 Ohm resistor to prevent a high frequency short.
I should measure the distortion of the dedicated transformer and the transformer from triad loaded with a dummy capacitance. Also this transformer is used for bass, so the core has to be big so it won't saturate and modulate the high frequencies. I think a good test would be to do the IHF IM, using 60Hz and 1KHz tones and look at the intermodulation products. This may not apply for electrostatics that do not produce any bass. I am a guy that measures first and then listens.

 

[ESLFan]

Sorry this post does not really help with your project. I don't know where MartinLogan sources their transformers. Since production is in Ontario, Canada, a good bet is that they are working with Hammond because they have the experience making ESL transformers since the 1970s, in addition to making tube output transformers. If you are looking to get an oem transformer for those panels you are putting so much effort into them, give them a call to see what they come up with.

 

[zinda]

As some of you know, for the last several months I've been developing a hybrid ESL speaker around Quest panels, I decided to move this to its own thread going forward. This speaker will fit somewhere in between the 13A and 15A for size and use the same panel over woofer design.

Construction
The main construction of this speaker will be laser cut 3/16" steel, including the woofer enclosure. The woofer enclosure is 2 cubic feet sealed, it uses 5 internal ribs that wrap all 4 sides for bracing. The ESL panel is supported by steel uprights that are tied together at the top, the panel itself actually adds quite a bit of strength to the whole part.
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Drivers & Components
The ESL panels are from the original Martin Logan Quest, these are only a little bit smaller than those used in the new 15A speakers.

For the bass sections I will be using the Sovereign Pro 12-500 pro audio woofers from Fane Audio. I chose these for their low moving mass and very good frequency response in the 100-500HZ range, they also cost under $350 Canadian for the pair.

I'm using the original OEM power supplies with a pair of MULTICOMP PRO VTX-146-050-106 toroidal transformers wired together to get the correct winding ratio. Original transformers from Martin Logan are no longer available for this panel. Below is the wiring instructions courtesy of Jazzman here on the forum, he also was the one to suggest using these trannies so all credit goes to him.

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Crossovers
The entire speaker will be ran off a Dayton 4X8 DSP unit, I will not be using any form of passive crossovers on the woofer or the panel. I will probably be crossing the ELS panel over with a 350HZ highpass @ 24BD/octave and the woofer will be bandpassed at 350hz and 60hz. The lower bass extension from 60hz and down will be handled by a corner loaded line array of 12" subwoofers.

Testing and development
I brought the panels and power supplies home to give everything a thorough test run with real power and real music. I wanted to do this since I got these panels second hand and wanted to be 100% confident there were no hidden issues. I hooked them up to my Jeff Rowland Model 1 (50W & stable into 2 ohm) and played music throughout the evening while using the Aerius 8" woofers for a little bass support. The panels worked flawlessly as expected and the aftermarket transformers worked great.

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With a solid test run successful I'll get the rest of the parts sent to the laser cutter to complete the metalwork of the speaker. The rest of the steel might take a little while because I won't be sending it to the laser cutter until I have another large order from work to go at the same time.

I'll continue to update this in the coming weeks. Right now I'm extremely busy with work so I'm not sure when more progress will be made. If anyone has questions ask away, we're all here to learn.

After reading through this thread, I felt so much in common with so many posts (probably everything but the transformers) . Since I spent many years welding and doing my fair share of projects. One being a river tube sound system that has to be solid welded and air tight. Planning alone will take a full 40 hours just designing simple stuff. I worked with 16ga paintlock and cut everything on a shear. Of course it was round design that was all self contained with a wheel chair battery in the bottom and an amp mounted fins on the inside curve so the heat transferred to the body and water ccoled it.

A 12" woofer mounted in the upper part withe magnet going into the lower part when put together
An alpine 3 shuttle deck mounted face up with a cover that kept it from water splashing. 4 speakers with curved back plates inset and 4 piezo tweeters, the top piece acted as a band pass for the sub with 2 ports . Wired so no matter what side was facing you it would be a stereo sound.

All welding was done with tig torch and fused as much as possible with silicon bronze filler where needed. Even something just 16" round and the bare minimum of hold downs and extras with minimal braces has hundreds of inches to weld. There was a solid 40 hour week just to get it together and numerous updates and changes came after each run.

It took 4 times before it was considered done. It was such a a perfect build, got lucky with the sub hitting hard and everything just worked. It was the one thing that never needed attention even though small rapids. It never tipped and was the safe place to store keys and money. I still have it 20 years later. Many fond memories of crazy dancing girls that came along and others that jumped on our huge fun islands. My last addition was trying to figure out how to add a pole to the fun island platforms. You tuned with me and you barely got wet, paddles and electric air pumps made hitting the water fast and enjoyable.

Others talked about seeing Metallica and small venues. I saw Metallica open up for WASP (talk about a great stage show) in a gymnasium basketball court, they had a full bar set up on a side stage, by the time WASP came on the place was thinning out since everyone was so drunk they were lying o!the floor against the walls! We ended up right up front thanks to all the light weights puke n passed out.

I ran those laser cutters back in metal fab days, I was supposed to become a data entry for them but I was needed to be the shops maintenance mechanic. I think now of all the stuff I could have made even just using the control panel on the machine. I was into car audio then and made my share of that stuff but I see know how easily I could have started making ESL parts and of course slot machine parts that aren't available.

I'm too old to get back in the trade and have no idea what they'd charge me to make parts. I have a book that teaches the computer entry side of it but never had the chance to get paid to do it. I understand exCtly how much planning went into this and commend you on the effort.

There is a metal called "mute metal" it's made out of 2 pieces of paintlock and has a layer of silicone between the sheets. It makes no metal sounds. It can be duplicated by simply smearing silicone caulk between sheets. It can be welded if you're careful. I had access to acoustic insulation to line my project.

Now .wondering what happened to this project. I hate reading a good project like this and not knowing the outcome!

Have to say high to Jazzman, most interesting and informative contributor on every site he visits!

What color are you planning on? With so many flat geometric sides there could be a very cool contrast of the right color is used. Dark will hide the complexity and light will highlight areas that aren't perfectly clean and show welds. It will be interesting to see complete.

My only concern is with the sub enclosures not being fully welded. I wouldn't trust silicone to stop any rattles or vibrations, there's so many pieces that can become active with resonance if the ends aren't terminated fully. Metal thickness doesn't stop resonation but will stop pressure from puckering , they are vastly different actions. Typically I made metal enclosures round to defeat that from becoming an issue. I'd say that drums are a good example of defeating resonance.

Many sub designs and even speakers use round cardboard tubes as a cheap and easy way to make enclosures, they don't require bracing (even with thin material) and defeat resonances (to a point depending on length).