# Hybrid Electrostats



## Jazzman53 (Jul 31, 2013)

My speaker is a unique hybrid ESL _beam splitter_ design that combines a line-source electrostat with transmission-line bass, in a compact affordable package. 

The_ beam splitter_ was a design solution which allowed placing the large transmission-line bass box directly behind the electrostat panel, rather than a side-by-side arrangement. The bass box has a "V" shape facing the panel, which forms the beam splitter. The angled surfaces of the splitter deflect the panel's rearward sound out the open sides of the speaker, rather than bouncing it back to the panel. 

The electrostat panel is a symmetrical push/pull sonic motor; consisting of a plastic diaphragm suspended between two conductive screens (stators), and powered by high-voltage electrostatic attraction/repulsion. A separate power supply puts a fixed DC voltage on the [driven] diaphragm, while the music output from the amplifier, routed through a pair of step-up transformers, puts the driving AC voltages on the stators. And the ultra-light diaphragm responds with great speed and precision to reproduce the music with exquisite fidelity.

The ESL panels and power supplies are actually quite simple and less expensive than most people imagine. As with any DIY speaker project, the woodwork is the hard part, and the woodwork in this design is no easy task. The simple ESL panels and power supplies could also be used with a simpler wooden frame and basic sealed or ported MDF woofer box and still give that magical ESL sound and imaging. 

(Google search Jazzman's ESL Page to find a more extensive write up materials links & detailed instructions) 

Wood: Red Oak frame, woofer box MDF sheathed with 5mm oak plywood. 
Overall dimensions: 15”W x 67.5”H x 21”D

ESL panel size: 12” x 48” 
Stators: 20-gauge perforated steel, 1/8” diameter holes / 40% open 
Stator coating: Automotive polyurethane-- black base, 12–14 mils clear topcoat 
Diaphragm: 6-micron Mylar C, tensioned to 1.5% elongation. 
Diaphragm conductive coating: 1 sprayed-on coat of Techspray Licron Crystal ESD
Diaphragm-to-power supply contact: copper foil tape perimeter charge ring
Diaphragm-to-stator spacer material: 3M polyurethane foam tape, .062” thick x .75” wide 
Diaphragm-to-stator spacing: 0.062” 

Transformers: 50VA 230V/2x6V toroidal (2 per speaker), wired for 76:1 step-up (alternate: 50VA 2x115V/2x6V)
DC Power supply: 115VAC input > 115V/230V transformer >8-stage diode/cap cascade 
> 18Mohm output charging resistor > 2.7KV DC output 

Woofer: 10” Aurum Cantus MkII, 8-ohm
Woofer box: Beam-splitter/ 9ft bi-folded transmission line
Crossover/EQ: Behringer DCX2496 digital 
Crossover frequency: 218Hz, 48db/oct Linkwitz Riley 

Below: Right speaker and Ripole sub 
 

Below: Stuffing the Transmission line (.5 lbs/ft3 polyfil). The line is curved behind the woofer to ensure the 
back wave energy can't rebound to the cone and color the sound. 
 

Below: Gluing the side rails to to the splitter box. 
 

Below: Finished cabinets (these were a lot of work!)
 

Exploded view of the ESL panel:
 


Below: Finished stator with edges ground smooth & polyurethane coating applied

 


Below: With the diaphragm pre-tensioned on the bike tube stretcher jig, the stator is bonded to the diaphragm with 3M foam tape. 

 

Below: Stator with foam-tape spacers & diaphragm attached
(foam tape bonds the diaphragm instantly & greatly simplifies assembly) 
 


Below: Opposite stator with foam tape spacers & copper foil charge ring. When the panel is assembled, 
the charge ring conducts the biasing voltage onto the diaphragm.
 


Diaphragms masked & conductive coating applied: 
 


Below: Stators completed / Preparing to assemble the ESL panel. 
 

Transformer & DC Power Supply Schematic: 
 

Electronics Package (toroidal transformers & DC power supply... a piece of cake):


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## dougc (Dec 19, 2009)

Those are great - your design?


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## cavchameleon (Jan 7, 2008)

Very nice build!!! The wood work looks farily complex though, not something I'd like to take on. Thanks for sharring!


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## Jazzman53 (Jul 31, 2013)

dougc said:


> Those are great - your design?


Yes, the beam splitter transmission line and woodwork are my design. Other elements of the electrostat & power supplies were gleaned from Roger Sanders' _Electrostatic Loudspeaker Design Cookbook_ and from other builders on the DIY Audio Forum. There is a wonderful corroboration between ESL builders on that forum.


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## Jazzman53 (Jul 31, 2013)

cavchameleon said:


> Very nice build!!! The wood work looks farily complex though, not something I'd like to take on. Thanks for sharring!


Thanks Ray, 
Most builders opt for a simpler bass box and frame. Fortunately, the ESL panel and electronics are fairly easy. In fact, I assembled the stat panels and power supplies from scratch over a 3-day weekend.


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## Jazzman53 (Jul 31, 2013)

cavchameleon said:


> Very nice build!!! The wood work looks farily complex though, not something I'd like to take on. Thanks for sharring!


I had no idea the woodwork would take me over a month of evenings and weekends to complete. The plywood sheathing and edge trim on the woofer box was especially onerous. I'm glad I have them but I wouldn't do it again. 

I've drawn up an easier version that retains the frontal oak frame but omits the glued-on 5mm plywood sheathing and edge trim from the woofer box. This would save a ton of time.


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## B- one (Jan 13, 2013)

Great job on the speakers they must sound amazing! I wish I was brave enough for something like that, but I know better.


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## theJman (Mar 3, 2012)

Some of you folks in the DIY world simply amaze me. I couldn't even conceive something like that, let alone build it. Incredible job... :T


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