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Old 15th March 2011, 02:23 AM   #81
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Join Date: Feb 2008
Location: Jackson,michigan
Alex, I sense your fustration with me and I very much appreciate your patients.
As you have helped me alot to understand how to go about what I am trying to do.

I knew it would a matter of a day or two that a light would gone on and now it is burning brighter than ever, thanks.
Thankfully it has been less than a day.

So, lets see if I can clarify a few things.

The name of this thread is " how to make a good transformer for a ribbon tweeter".
Hence " tweeter " the lowest frequency was never specified.

So, in my mind I'm thinking I have gotten good results from the cores that I have and it would be only a matter of adding a secondary winding to keep things simple. Right?

Then In the back of my mind I thought this would work for a small bass panel aswell and this is where all the confusion started.
Because now I am thinking full range and everyone else is thinking tweeter. Without me realizing it.

My bad and I'm very sorry for all the confusion I have caused everyone and I apologise for any sharpness that I may have displayed.

Then when you mentioned cable x-former and balun,I instantly started thinking rf stuff and powdered cores.
It was then I really started to confuse my self even more.
Because I was not familar with the term "cable x-former".

Then got to thinking that with a transformation ratio of 20:1 I could use 20 turns for the primary and still get down to 200hz at 100 watts with this core without saturation and one heavy turn for the secondary.

I am familar with this technique from my days of messing around with solid state rf power amplifiers.

It was then that the light went on and I had realized what you and Bear were coming from and trying to tell me.

So therefore, I am very sorry to both of you for my ignorance and sharpness as it was uncalled for on my part.
I really feel like idiot.



Anyway, I have taken a closer look at the core that you had suggested and it is very nice indeed.

The B-H curve of the core that I have is the best I have seen and compared, too, anything else that I have on hand.

But nowhere as good as the one you have suggest indeed.

But the price would be about $70 to $100 (maybe more) each after tax and shipping.
Not to mention a minimum order of 20 pcs.

I did discover those last year aswell.

Thats when had discovered the company called ALPHA CORE.
They have some in a more comparable price range that suited my needs at that time.

Unfortunatly for me at the moment I don't have funds, and ,will consider this more as soon as my situation has been resolved.

I have included the B-H curves of my core and the data of the core you suggested for all to compare.

And hopes to persude anyone whom has the funds too invest in a quality core.

Although one should not despair ,because good results can be had with what is available.

I still stand firm on this.

My goal here was to show how to do it.

Again I am very sorry for the confusion.

I glad I had realized my mistake before I had wasted 36 yards of copper tape only to find out that it would have been less than optimum performance.

Meanwhile, I am currently working on the magnet structure and frame with an adjustable gap for the 4" ribbon. jer
Attached Images
File Type: jpg B-H%20curve%20for%20p3.jpg (1.5 KB, 620 views)
File Type: jpg B-H%20curve%20for%20p4.jpg (1.6 KB, 614 views)
File Type: jpg B-H%20curve%20for%20p5.jpg (1.5 KB, 613 views)
File Type: jpg B-H%20curve%20for%20p6.jpg (1.5 KB, 613 views)
File Type: jpg scope%20graph.jpg (57.6 KB, 583 views)
Attached Files
File Type: pdf vergleich nano-ferrit_1_e.pdf (84.6 KB, 45 views)
File Type: pdf vergleich nano-ferrit_2_e.pdf (75.3 KB, 27 views)
File Type: pdf vergleich nano-ferrit_3_e.pdf (148.7 KB, 19 views)
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Old 15th March 2011, 05:20 AM   #82
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Yep...
The last time I quoted FT-3L (the one you need) from Metglas, in container (much better then impregnated) it was around $200 per kilo. The suggested core would be 245 g <=> $70-100 Oh, well...
Another suggestion then.
Amorphous core is ten times cheaper and still beats ferrite and steel. 2605SA1 Talk to them and ask for the one with transverse anneal. You may even specify the permuability level. Very linear curve, some audio transformers has similar cores
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Old 15th March 2011, 05:36 AM   #83
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Thanks Alex,I wiil look into them,
Even though this one works,I too would like to get some better cores for some future permenant builds for both, my ESL's and the mini apogee's I plan to build for my friend in florida. jer
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Old 15th March 2011, 07:52 AM   #84
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I needed a way to measure the magnetic field so I created this handy little tool.
A magnetometer.
It is not calibrated be any means.
But it does allow me to check the uniformaty of the magnetic field.

I found that even a gap of a 1/4" to an 1/8" between the ends of the magnets showed a reduction in the field strength by as much as 50%.
At a measuring distance of 3/8".

Since I could not gain any significant amount length to warrant the reduction in strength I set the magnets touching end to end.

The field strength is compleatly uniform across the entire length. jer
Attached Images
File Type: jpg MAGNETS.jpg (43.1 KB, 585 views)
File Type: jpg MAGNETOMETER CLOSEUP.jpg (58.4 KB, 579 views)
File Type: jpg MEASUREMENT SETUP.jpg (47.3 KB, 577 views)
File Type: jpg MAGNETOMETER NO FLUX.jpg (30.4 KB, 521 views)
File Type: jpg MAGNETOMETER WITH FLUX.jpg (21.0 KB, 170 views)
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Old 16th March 2011, 05:41 AM   #85
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quote from Peca,
"What you think about idea to winding secondary coil maybe with litz (stranded) wire to avoid eddy current in transformer?"

Acording to the clemson calculator a wire dia. of .038" (18 gauge) is the point were the a.c. resistance (impedence) starts to rise and is significantly high with a 12 gauge wire.

I think that it would be safe to assume that litz wire would be a wize choice for a secondary (or primary) winding if more current capablity Is required than an 18 gauge wire can handle or if a suitable size flat conductor can not be determined.
As flat conducters can be hard to work with at times. jer

Last edited by geraldfryjr; 16th March 2011 at 05:46 AM.
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Old 17th March 2011, 03:02 AM   #86
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I was trying out the magnetometer today and it infact shows the addition of field strength as layers are added.

For instance one layer was a two point drop on the graticule and two layers showed a drop of four points , three layers six points and so on.
Neat! jer
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Old 17th March 2011, 09:37 PM   #87
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Hi DIYers!

Tinitus, if you can see my messages to you, please go with me something on private before I wiil publish my posts here!

Peca
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Old 5th May 2012, 09:14 PM   #88
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Default Ribbon tweeter Matching Transformer That really Works

I had some of those Pioneer Tweeters and the transformer was a joke! I tried regular iron cores, and they are more than 50 percent lossy, so tried Ferrite. The size of the core is 2 3/16 inches square and no gap. It is wound based on RF tech, so not an easy job. For ribbon resistance of .03 ohm, which is what the ones I made are, the ratio is 17 to 1. just for 36 watts, that is 36 amps on secondary! I used 5 mil copper sheet that is wound so it is a tube when done. layer of foil, wind 16 turns of 2 ea #21, then another foil. Side ends are pinched together and soldered making it a flatened tube. 4 of these in series to complete it. The connection ends of both of the foils has a piece doubled over and soldered. This is because of the high current. I tested it for the amount of voltage it would take with little loss. For 3 Kc lowest frequency, it would take 35 volts RMS, which at 8 ohms is over 150 watts! The ribbon won't even handle that! This has almost 100 percent coupling, and very little loss.
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Old 1st September 2012, 05:34 AM   #89
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Quote:
Originally Posted by alexberg View Post
Yep...
The last time I quoted FT-3L (the one you need) from Metglas, in container (much better then impregnated) it was around $200 per kilo. The suggested core would be 245 g <=> $70-100 Oh, well...
Another suggestion then.
Amorphous core is ten times cheaper and still beats ferrite and steel. 2605SA1 Talk to them and ask for the one with transverse anneal. You may even specify the permuability level. Very linear curve, some audio transformers has similar cores
"Amorphous Core is ten times cheaper" ? You just quoted what looks like about $400/ KG for Metglas (Amorphous Metal core)
At any rate, this is insanity for this product. Might reflect the monopoly Hitachi had on this market. AT&M (china) now cranks out 40,000 metric tonnes of Amorphous Metal ribbon per year. Ya!, and Hitachi makes twice that. This is "power grid" transformer stuff'in (high efficiency) The demand is high, but I read somewhere, $3/ Kg I'm pretty sure they where talking about the foil (ribbon). And their own marketing shows Metglas built grid transformers at only 25% more. Which means manufacturers of such ( there are many) can't be paying that much.
So if we could get our hands on the ribbon, could we make our own cores. Nice money when you can get it Hitachi; 3 bucks will get ya $300. A 10,000% mark up. This just begs DIY.
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Old 1st September 2012, 11:20 AM   #90
AndrewT is offline AndrewT  Scotland
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why can't we just use air core transformers for tweeter driving?
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regards Andrew T.
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