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Inspired by the great Quad ESL 63, I designed a derivate from the ESL 63 with a wire raster stator instead of the perforated plate stator used by the famous Quad ESL 63. According to my own experience with DIY ESL's, raster stators seem to give an ESL better sound reproduction properties and a higher efficiency.

The first challenge in the stator design was the question: "How to create electrical wire in circles?". At the moment I was trying to solve this question, my two year old son ran to me, to show me a web of a spider in our garden. The structure of the web gave me an exact answer.

This drawing was made after my son showed me the web of the spider

The second challenge was to convert this structure in a design which I can make with my relative simple DIY tools. I spend approximately 9 months to design the ESL in cad cam software and I gave my project the name "Spider ESL".

The electrical wire I used is the ROMAL (0,75 mm2 with PVC insulation) wire with a outer diameter of 1,77 mm. The D/S spacing chosen is the same as in my other DIY ESL projects (approximately 2,5 to 2,6 mm). The step-up will be the Amplimo VDV106 ratio 1:75.

The mylar used has a thickness of 6 mu and the Mylar coating has a high resistance. I used all parameters of my old DIY ESL's to be sure it would work. During this design process, I had to experiment with several structures to fix the stator wire to the stator-spars in the middle sections.

Above you see the cad cam design of the Spider stator. In this drawing you can see the circle segments which are to be connected to the Quad ESL 63 delayline. This will create a virtual point source behind the elements for sound reproduction (see drawing below). For details I refer to the bulk of info you can find on the Internet.

The tools I had to make before the building process started

A stator without the wires

There after the third challenge of this Spider project started, the building process of the Spider stators. This process took some time because of the complexness of the whole design. I knew that the key to success was to follow my design with great precision and care. To achieve this goal I had to create special tools for drilling holes at the exact positions and cut the stators exact according my design.

After a few month I succeeded in building the 4 stator elements. I placed the project in the hold for nearly two years. Partly because I was tired of it and partly because I didn't know how to create the delay circuits tuned for the Spider ESL. A few month ago a fellow ESL builder, Rob de Lugt, called me. He had two original Quad ESL 63 delayline circuits for sale. Because I didn't know if the original Quad delay lines would be able to drive the Spider ESL's, I had to think about it first. My Spider stator segments will have a different capacitance than the Quad elements. I wasn't sure if the delay circuits would accept the Spider elements. But in the experimental world nothing is certain, so I bought them.

Applying the wires

Inner structure of the Spider ESL elements

Outside structure of the Spider ESL elements

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Testing

After connecting the ESL's to the amp and turning the volume up the Spiders came to life for the first time. The sound production was much better than I expected ! The Spiders give a very nice transparent, natural and precise sound reproduction. During one session we compared the Spider ESL's with the Quad ESL 63. Although we could hear the Quad and Spider are family, the Spiders proved to be superior to the Quad ESL63! The Spider is more open, better balanced and the reproduction of voices are more natural.

My hypotheses that a wire stator is superior to a perforated plate stator in an ESL element, seems to work also in the ESL 63 design with delay lines.

Designing and building the Spider ESL was a great challenge, with a result beyond my own expectations !