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Old 28th March 2011, 11:14 PM   #81
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Beautiful work, Roger!

After you've finished tweaking, I'll be anxious to hear your impressions-- especially in comparison to your hybrid speakers.

Charlie
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Old 29th March 2011, 05:58 AM   #82
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Hi Roger,

Very beautiful, indeed. Let us know how you like the sound.

Wachara C.
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Old 29th March 2011, 09:11 AM   #83
SM7UYJ is offline SM7UYJ  Sweden
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I do'nt think any one was fooled, but the surface is NOT polished paint - It's 3mm black Plexi!

Roger
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Old 29th March 2011, 10:49 AM   #84
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have you read this thread ?
Step-up transformer design


I had started this study last year on such issues.
I had to put it on the back burner for a while due to lifes issues that happen to come along and revamping of my studio and project room.
So I haven't had the chance to compleate it yet .

I will continue to do so, as soon as, I finish tidying the up some things around here.
It won't be but a week or two (maybe less) now that the weather is warming up so that I can transfer the mess to my garage and get it organized.

I believe there are some other important sections scattered in other threads aswell in the
same time period (a year ago) as I had several things (way too many) going on at the same time.
I will try to compile them for you.
Or you can do search on my previous posts of that time frame ,about 12 to 14 pages back is where I left off. jer
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Old 29th March 2011, 12:52 PM   #85
SM7UYJ is offline SM7UYJ  Sweden
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Hi jer,

Yes, I have read this very informative thread - once again today after your post!

My hope when starting my other thread, was getting input/tips from people who have made ES transformers specialy made for LF.

All the information I manage to find, seem to be used in hybrid systems or they do not specify how the transformer for the bass section was made.

I'll try to rewire the primary to get the inductance up, and also try to lower, or omit, the resistor used on the input!

Roger
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Old 29th March 2011, 03:44 PM   #86
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I like the black plexi and had anticipated on building my final frames with it aswell.

In order to get a low frequency you have to use more turns on the primary and of course more turns means a lower transformation ratio using the same secondary winding and we don't want this of course.

Every time you double the primary turns the saturation frequency drops on octave.
In order to combat this is to use a larger core and thats when I started stacking the cores.

I don't remember as I will have to look back on the data, that, every doubling of the stack (core area) also lowered the saturation by an octave (or 2?? ) aswell.

With the quadstack I had gotten good results as far as a low saturation frequency is concerned.
But, there were a few issues that hindered it's performance.

I had found that my transformer cores have a winding capacitance of around 400pf.
My little panel has a capacitance of 50pf and since it take two match up to the same level of my woofer we will assume a load capacitance of 100pf.

I used a 10 turn primary as a compromise between effeciency and lowest saturation frequency of about 200hz to 300hz (again I have to check the data) with a voltage input of 80v peak to peak (ie, 100watts).
This gave me a transformation ratio of 1:215 with my core.

So one would think 1:215 ratio,100pf that's aprox 4 ohms at 20khz right?

WRONG!

My actual load capacitance with a Tc of 400pf + ESLc of 100pf =500pf.
This brings my actual amplifier load impedence down around the 1 ohm range or lower at 20 khz.

In my situation 80% of amplifier power was being dissipated in the transformer capacitance and and 20% of the power in the panel.

This doesn't bother me at all as long as the voltages required to drive the panel are there. And is all what matters to me.
However,The amp didn't like this at all!

While it was struggling to find the current it need to supply the load, it would stop midway and this is where crossover switching (crossover distortion) became realevent.
During this period of time the amplifier was not in control of the transformer any longer and the energy stored up in the transformer starts to oscillate (ring) at a frequency coresponding to the leakage inductance and the total capacitance basicaly becoming a tesla coil.

It was this RF that destroyed all of my cheapy meters any high value resistor I had tied to the secodary that theroeticaly should not have burned up.

So stacking more cores and adding more windings added more capacitance and lowered this resonate frequency well into the audio band.
And as low as 10khz with the quad stacked cores on some tests.

Now, It is bad enough that the amp as to supply power to a 1 ohm load through the transformer, but,the transformer appears as a short circuit to the amp when it tries to supply energy at the resonate frequency of the transformer.
And thats when the amp would self protect and shut down due to overload.

I know that adding a resistor in series with the primary helps to dampen this resonance.
In my case my load was already 1 ohm and adding a 2 ohm resistor dropped my voltage to 1/3 of what it was driving it with.

That brought my efficiency down from 20% to 6.6%.
And that is what it sounded like 6 watts with 100 watts of drive power.

After plugging the data into my spice program I found that .3 ohms was all I needed and the resistance of the primary winding was enough, as it was just a thin gauge speaker wire.

The other problem with quad stacking the transformers is that I used a common primary for all of the cores.
This was good as far as saturation frequency is concerned.

But, the secondary windings were kept to each individual core and wired in series.
This did not increase my transformation ratio as one would expect but kept it the same as using a single core.

Here's why,
The primary winding see's the total area of the four cores and secondary windings only sees 1/4 of the total core area.
So the induced emf on a secondary winding was 1/4 of the total emf induced by the primary winding.

Wiring the secondary windings in series brings this factor back to 1.

Thus,
Keeping the transformation ratio the same ,but reducing the saturation frequency to 1/4 ,that of a single core.
But at the same time raising the capacitance by factor of 4 aswell.

This is not good.

I found that the capacitance of the transformer also exactly matched that of the surface area of the core to some typical values of insulation thickness and dielectric constant.

On the quad stacked cores I was able to get down to 15hz to 30hz range when saturation started to occur with a 20 turn primary and a 80v p-p input.

The quality of the signal in that range was okay but not the best.
I'm sure the quality of the core material has everything to do with this.
These slight distortions that low, I doubt, would be very noticable, if, at all.

There are few here that could make better recommendation of core material than I, such as ,Alexburg or Bolserts just to name a few.

My esl's at the moment are hybrid but I do require a transformer that doesn't saturate as low as the 150hz to 250hz range.

Alexburg referred too me a very nice amorphous core, but, it is not available here locally and would cost me over $200 a piece with a minimum order of 20 pieces, I just dont have that kind of dough.

Over here I found a company called alpha core that I could get a quality 1800 watt toriod core for less than $30 a piece and this would get me 20hz at 200watts or so, maybe more, with minimal amount of primary turns thus keeping my secondary to a single layer.
They do have amorphous cores aswell, and again, are very costly.

I have no issues with the quality of sound using the standared core.
I have done some quick distortion measurements, although not scientifically controled I have not found any significant rise in THD throughout the audio bandwidth.
I plan to do a complete investigation of this aswell.

This where I had left off,
To show the effect of primary winding coverage vs leakage inductance ,and ,a flat conducter vs a round conductor compared to leakage inductance.

Then dismantle the whole thing and add an an appropiate amount of insulation to the core as this should greatly reduce the capacitance.
Then rewind the thing and test it again.

The result i'm sure will be much better than stock.
Using the same core, I started this whole study with.

I hope this helps you to understand better. jer

Last edited by geraldfryjr; 29th March 2011 at 03:47 PM.
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Old 5th April 2011, 11:51 PM   #87
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Congradulations on your fine work! You might have connsidered varying the ESL segment sizes ML does to spread the resonances around.

I have the ML CLX and had upgraded the Solen crossover caps to MIT RTX and PPFXS film and foils. This improved the resolution. I also mounted a Raven R 2 Ribbon on 30 lb fishing line suspended from a custom made semicicular metal plate from the top. This greatly improved high frequency detail despite the tweeter having to play through the speaker. The Teflon cap and aircore foil inductor crossover are mounted in the speaker base and the 22 guage silver wires run inside the outer frame of the CLX (which can be removed with a hex key). The tweeter leads are brought out at tweeter height making the addition lack visible means of support and no permanent mounting damage to the speaker.

nyc 012.jpg

nyc 014.jpg

Last edited by ticknpop; 6th April 2011 at 12:17 AM.
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Old 6th April 2011, 12:49 AM   #88
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The bass transformer in the CLX is an EI core about a 5 inche cube in size, the high frequency transformer is a torroid. Have you seen the Plitron ESL tranformers? There are planar power film resistors in series with the LF transformer which can be switched in and out to adjust the LF level.
The crossover is a air core choke in series with the LF transformer. The high frequency crossover I haven't plotted out in detail yet, but is a multipole with a notch filter

Last edited by ticknpop; 6th April 2011 at 12:55 AM.
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Old 6th April 2011, 07:39 PM   #89
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Quote:
Originally Posted by ticknpop View Post
The bass transformer in the CLX is an EI core about a 5 inche cube in size, the high frequency transformer is a torroid. Have you seen the Plitron ESL tranformers? There are planar power film resistors in series with the LF transformer which can be switched in and out to adjust the LF level.
The crossover is a air core choke in series with the LF transformer. The high frequency crossover I haven't plotted out in detail yet, but is a multipole with a notch filter
Hello ticknpop,

Thanks for posting the pics for your CLX panels
Any chance you could post some pics of the transformers and crossover you described?
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Old 7th April 2011, 07:45 AM   #90
SM7UYJ is offline SM7UYJ  Sweden
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Quote:
Congradulations on your fine work! You might have connsidered varying the ESL segment sizes ML does to spread the resonances around.
Thank you!

The segmentation is actualy not the same for the cells, but the variation is not as big as the MLs and I try to keep the number off cells to a minimum!

I understand the theory off spreading the reconance off the panel by different segmentation, but I do not like the nolinearity off the membrane that this causes.

My spacers are mainly there to help stability, and if I could I would only have vertical spacers as i belive this would allow the membrane to move as linear as possible!

Roger
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