Another ESL speaker project

Jazzman53

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Hi all,

Since October of last year I've been toiling away on my biggest-ever ESL speaker project, and I'm very happy to be nearing completion after 5 months of exhausting work.

Several of my Carver Audio friends have twisted my arm for years to build speakers for them, but until now I've declined because my designs are exhausting builds, especially for an old guy like me. My friends prefer my lightweight OB hybrid speaker because it's prettier and easier to transport than my other designs. I must have bumped my head somewhere because I finally agreed to do it.

I'm building four (4) pairs of the OB design which uses a 12" woofer mounted on a modified H-baffle. The frames are red oak and the stat panels use segmented wire stators which electrically bend the wave front from planar to cylindrical. Bending the wave front is accomplished using a stepped-frequency/phased-array of (15) wire groups which drive the diaphragm sequentially from the panel centerline outward.

The stator wires are 20 AWG, UL-1061 SRPVC-insulated, single-strand copper. The HV bias supplies are simple 3.2kV diode/capacitor cascades, and the step-up transformers are tandem pairs of 50VA 230V/2x6V toroids wired for 76:1 step-up ratio. The diaphragms are 6-micron Mylar C with a 2-micron Licron Crystal ESD coating giving E7-E9 Ohms resistance. The speakers are bi-amplified using a DSP crossover.

Below are a few build pics and three videos showing the stator/panel build process and a completed speaker.

Enjoy!


Wire stator build video:

https://youtu.be/814iWnmz6_4

Panel assembly video:

https://youtu.be/ECM3gfrJPxQ

Completed speaker video:

https://youtu.be/Q_4sddiBEoU
 

Jazzman53

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sorry all....had to move this thread to the DIY Speakers section.
 
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Jazzman53

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I appreciate your compliments on my speakers—it was quite a journey getting here.

Unsegmented wire panels sound exactly like a perf metal panels, but wire does give some options that perf metal doesn’t.

The downsides to wire are the requirement to stretch it to straight condition, which requires a very stout jig, and the wires need a support structure in the stator; which adds up to a lot more work.

The upsides are the increased reliability/arc resistance afforded by the PVC insulated wire, and the option to tailor the panel’s dispersion for a wider sweet spot, using segmentation.

Segmentation works something like what Quad did in their ESL-63 and later models-- except where Quad stators use concentric ring conductors powered thru a delay line to emulate a point source projecting a spherical wave front, segmented wire panels use discrete vertical wire groups sequentially powered by stepped-frequency/stepped-phase signals to emulate a line source projecting a cylindrical wave front.

It sounds complicated but it’s rather easy to do by merely inserting the right value resistors between the wire groups. The resistors in series with the wire capacitances in parallel form a series of low pass filters which tailor the dispersion. There’s even an Excel spreadsheet program posted at the DIY Audio Forum which does all the math and computes the resistor values.

I have to say though; as great as my segmented wire panels are, nothing beats the imaging from flat perf-metal panel in its focal sweet spot. My panels have a wider sweet spot, which is nice when company drops in, but it comes at the expense of giving up some of that magical imaging.

I have a lot more photos and info on wire ESLs on my website here: http://jazzman-esl-page.blogspot.com/
 
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Jazzman53

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IMG_2268.jpg
 
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