How to make a good transformer for ribbon tweeter?

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It all depends on the wire gauge you use and and length of the wire used to get your selected turns ratio.

There are many ways to combat this ,from wire size to multiple windings in connected in parallel.

The latter being more ideal as this would increase core coverage and reduce the leakage inductance.

For practicablity reason by using multiple windings in parallel, the DCR of transformer should be much less than the ribbon itself, not to mention the DCR of the transmision line feeding the ribbon from the transformer as well.

jer.
 
Most of us don't use garden hoses.
But that is about the right guage!
I would try (DIY) many many layers of aluminium or copper tape that you can find at your local hobby shop or hardware store.
Laminated with an insulating material like polyurethyn or something.jer
 
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Maybe I am missing something... no matter.

I want amorphous cores and good coupling between windings... LF response is of no interest. Since the secondary is few turns, that is why copper foil is used and not just a handful of turns of say 8ga. At least this is what I am told, having not made one myself.


_-_-bear
 
You seem to be understanding okay.
Just remember all of the same rules apply.
the larger the core ,less turns on primary(as per lowest frequency),therefore a lower overall DCR.
one reason for using a flat conductor as a winding is to increase core coverage to lower leakage inductance.
This where I had left off in my study due to equipment failure as I was pushing everything past a pheasible limit.
I had figured out that by just by spreading out the 10 turns of wind reduced the leakage inductance greatly.
And even more so when I used 4 10 turn windings in parallel to get complete coverage.
It was bolsert that told me that if you double the winding coverage you will half the leakage inductance.
I had found this to be true and I had planned to show this when I had burned up my last meter due to the highvoltage rf caused by the crossover distortion of the amp, in combination with the leakage inductance and transformer capacitance causing it to resonate,basicaly forming a tesla coil.
There is some info on using amorphous cores at 6moons.com . jer
 
From what I have been reading,manufactures are already using such metals as a standered practice.
It is just hard to pin point which product is using what metal unless you specificly order what you want.
But I can tell you this I have never seen the kind performance I get out of my toriod power transformer for audio.
I have several tube type OPT's laying around and have compared them too.
I have found that the doughnut takes the cake everytime ,ten fold!

As I have stated before where else can you find a transformer cheap that has a flat response well past the audio range,produces perfect square wave at low and high levels , is already made and all you have to do is add a few turns for a new winding.

Give it a thought or try, and let us know what you find and If I get to it before you do I will post my results as well. jer
 
for tweeter use the mains power cores have way high loss from too thick laminations

better HF "tape wound" core exist - are pricey

for ribbon tweeter use it could use the largest pot core, hi perm ferrite - a consequence of low V, high lf corner frequency

a problem with the required low R is that heavy wire/foil will give bigger loss from skin depth/eddy current in the copper too - the multifilar/bunched winding techniques may help
 
Good point.
However I,m not sure about the validity of your last statement as flat conductors are used in high power rf amplifiers to combat losses due to the skin effect at radio frequencies.
I don't think this is going to be as much of a factor at audio frquencies as having a high leakage inductance will.
And yes, the thinner the laminations the better,but the price factor goes up drasticaly as well. jer
 
If you google up "skin effect caculator" you will find many articles and discussions on the subject.

Basicaly by using a flat conducter you are increasing the surface area of the wire compared to a round wire of the same cross sectional area thereby reducing the effective resistance at higher frequencies caused by the skin effect.

The skin effect causes the wire to have more resistance at higher frequencies than it would if just a direct current were flowing through the wire.
This is why silver plated copper is used for coils in rf equipment,particularly highpower vhf and uhf amplifiers.

The effect of eddy currents in the windings are nulled by current flowing through it.

Eddy currents in the core are combated by using thin laminations.
The thinner material has a higher electrical resistance thus reducing the eddy currents that get setup in the core material.
Also this is why the laminations must insulated from layer to layer.

I hope this helps you to understand more throughly. jer
 
I was actually thinking of someting closer to "bus bar" than foil - after all the ribbon load is on the order of few 10's mOhm - say you need ~10x the ribbon length to get there and back and circle the core, if you want 1/10 th the Ribbon's R in the secondary then you need 100x the cross section area (less with Cu vs Al)
 
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Yes indeed,you stiil need cross sectional area to handle the current.

The idea with using a foil tape conductor is to try to make sure that all of magnetic lines of force are cutting through the winding by getting 100% coverage of the core.

For an 8 ohm/ .28 ohm (1:26) transformer at 100 watts your talking about 130+ amps so you must have enough combined cross sectional area to handle the current.

I got some 1/4" copper tape from hobby lobby cheap and can be wound around the toriod very easly.
At least that was my intension when a bought It except that I have been working on ESL's instead. jer
 
as just mentioned, the problem with thick fat stuff (square or not) is that you don't get enough coverage over the primary windings by the secondary... fine for power transformers, and that's how they used to build monster 5vdc power supplies. :D

Jer, I suppose that if you made a few windings with that 0.25" copper foil (to cover the toroid surface) and then ran them in parallel, you might have something.

_-_-bear
 
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