Please rec. step-up transformers for ESL

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Hi all!

I've been reading this thread (actually this complete forum) with great pleasure and interest and it has convinced me of building a pair of ESLs in the near future.
But some questions remain, of which one is in line with this thread, and I hope you can help me with this:

You guys here are talking about using 'normal, step-down' toroidal power transformers. The only toroidal power transformers of about 50VA Amplimo has (I prefer to use Aplimo because of my good experience and I can get them at a fairly good price), has two secondary windings and one primary. The lowest secondary voltage is 2x6V. Can use two of those trannies and get the previously stated ratio of 1:75? If yes, how should these be wired?

Kind regards,
Emiel
 
spacers

Hi,

spacer thickness should be chosen after frequency range and filter response. Roundabout 1mm (40mil) for frequencies from 150Hz/>12dB
or 200Hz />=12dB. I wouldn´t go down further since the panels width would have to become really big. Too, as soon as the diaphragm has to ´move´, distortion goes up significantely. As long as You keep beyond 200Hz distortion levels keep extremely small and dynamic headroom is more than plenty for HiFi. Efficiency can be quite high, because of the small spacings. All voltage levels ...wether it are the polarising- or the signal-voltages.... are quite low. Such panels can be driven with lower transformer ratios because they don´t need several kvolts to sing. Polarising voltages around 1.5kV and signal voltages of a couple of hundreds volts are enough. Which reduces the risk of corona and other undesirable effects of higher voltages.

spacer materials can be various sorts of plastic material that can be glued to the stator and the diaphragm. Try to get pure material, because You never know the ingredients of coulored stuff. Avoid grey or even black material because there may be carbon in. Take care about constant thickness of the material. Some clear acrylic material can vary quite much. Use material with a small dielectric constant. In Germany You can get a clear plastic foil (1mm thick, 1m wide) off of the roll in every DIY-market.

Easy to use are the foam-Tapes by 3M. They are quite costly, but spare time and nerves. You even can get them in a clear version, which is quite interesting with regard to optics (but use those only as supporters to the diaphragm and not as a mounting frame!)

jauu
Calvin
 

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