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-   -   Transformer-less Ribbon Driver? (http://www.diyaudio.com/forums/planars-exotics/215726-transformer-less-ribbon-driver.html)

mondogenerator 6th July 2012 03:20 PM

Transformer-less Ribbon Driver?
 
Ive recently got a pair of Fountek NeoCD3.5H (its a horn-loaded version), and they may/may not be a true 'ribbon'. The driver uses a polymer diaphragm with foil laminate, i think. Maybe its vacuum deposited.... I don't know.

Anyway, its low resistance, so requires a transformer to make it a manageable load for an amplifier.

But what if instead of a Aluminium ribbon, the ribbon would be conductive, but with a greater resistance?

Has this been done?

You could theoretically i suppose, find a good material, that in the correct thickness or cross-sectional area, would give a 2" ribbon a Resistance of 8 Ohms; for example.

analog_sa 6th July 2012 04:01 PM

What is the difference between a resistive ribbon or adding a series resistor? Either way you lose sensitivity. The transformer does the matching with minimum losses.

Groove-T 6th July 2012 04:15 PM

thinner foil = higher Resistance= lesser Current flowing= lower Efficiency= need more power

thinner foil = lower thermal capacity

more power & lower power handling = ribbon fails

Aluminium has good power handling, good damping properties, low structural resonances and pretty stable when corrugated or similar

mondogenerator 6th July 2012 04:32 PM

of course. Efficiency. One too many beers again. What would be the penalty for using copper instead or an alloy? Say duralumin. I guess im looking for an experiment lol

dheming 9th July 2012 09:21 AM

Beryllium foil would be fun to play with. Shame it's so expensive even for a small piece.

andyr 10th July 2012 02:09 AM

Quote:

Originally Posted by mondogenerator (Post 3083586)
Ive recently got a pair of Fountek NeoCD3.5H (its a horn-loaded version), and they may/may not be a true 'ribbon'. The driver uses a polymer diaphragm with foil laminate, i think. Maybe its vacuum deposited.... I don't know.

Anyway, its low resistance, so requires a transformer to make it a manageable load for an amplifier.

But what if instead of a Aluminium ribbon, the ribbon would be conductive, but with a greater resistance?

Has this been done?

You could theoretically i suppose, find a good material, that in the correct thickness or cross-sectional area, would give a 2" ribbon a Resistance of 8 Ohms; for example.

I've used a 5' long x 1/4" wide ("the thickness of a butterfly wing", according to the marketing blurb) corrugated aluminium ribbon for about 20 years ... as the tweeter in my Maggies. It has a resistance of 2 ohms. Later Maggie ribbons are only 3/16" wide and have a resistance of 3 ohms.

Regards,

Andy

a.wayne 10th July 2012 02:25 AM

Very low mass can be an issue , power handling aside, sound is thin sounding and has no percussive energy ..

mondogenerator 10th July 2012 09:14 AM

interesting, those ribbons must be extremely fragile. I had considered metalised mylar, or vacuum depositing on a similar film. Eg a large wide ribbon, micron level thickness conductor. In that way i could trial different metals, tho i guess Fe and Ni are bad ideas.

andyr 10th July 2012 09:52 AM

Quote:

Originally Posted by a.wayne (Post 3087003)
Very low mass can be an issue , power handling aside, sound is thin sounding and has no percussive energy ..

You obviously have never heard any "true-ribbon" Maggies.

Hie thee to thy nearest Magnepan dealer. :)

Regards,

Andy

bear 10th July 2012 12:55 PM

copper will not work, too much mass... there is an equation that puts all the pieces together. add mass and the sensitivity drops like a stone. Aluminum turns out to the best compromise so far.

Duralumin is simply an old aluminum alloy - no longer made, but a similar one exists today.

_-_-bear


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