Newest Segmented ESL

My speakers have evolved since I built them in 2008.  The oak beam splitter bass cabs have remained the same but the ESL panels have changed several times, in search of the holy grail of sound reproduction.  

First I used perforated steel panels which had great slam and imaging but beamed like crazy.  Then came the segmented welding rod panels which gave a much wider sweet spot and sounded wonderful but were just butt ugly to look at.  And now I have these lovely new oak lattice copper wire panels which sound as sexy as they look. 

These new panels are likewise segmented for wide dispersion.  An explanation of segmentation and how it works can be found HERE.  

The stator conductors are (90) single-strand 20awg copper wires with .010 XLPVC insulation and 43% open spacing.  The wires are physically divided into (15)  groups of 6 wires which are electrically powered as (8) discrete groups; consisting of the center 6-wire group and (7) left/right paired 6-wire groups on either side.   

The wires are supported by a lattice structure made of interlocking pieces of red oak.

The wires were first stretched to plastic deformation in a special jig to make them perfectly straight.  And then the supporting lattice was glued together over the wires, in the jig.   

Below:  Wires stretched straight

Below:  Interlocking oak lattice pieces 

Below: Lattice assembled onto wires



Below: A rear stator, spacers, charge ring

Below: Bonding diaphragm to stator

Below:  Front & Rear stators ready


Below:   The segmentation resistor network


Finished Speaker:

Bob Carver loves my new speakers!
Cellphone Video from Carverfest 2016

Everything else is two Dixie cups and a string :-)

Greetings all from the Jazzman,
I'm here to share my passion for jazz and hi-fi and do-it-yourself electrostatic speakers.  My electrostat panel and electronics are simple and the beam-splitter design combines a line source electrostat with transmission line bass in a compact, affordable package.        

It still amazes me that an average Joe with no electronics experience can build a speaker on the kitchen table that rivals the $20k commercial offerings.  And building the actual drivers from scratch takes cool to a whole new level.       

The links at the bottom of the page provide detailed build instructions, component sources and schematics.   

I am most happy to share with you my DIY electrostatic loudspeaker project.

Charlie Mimbs
Savannah, GA

Update 3/30/16:
Click HERE to view build pics of my newest and sexiest ESL!  

Posted 3/1/15:
Click HERE to view the build photos of my  segmented welding rod stator ESL's with selectable wide and narrow dispersion modes.  


How do they work?

If your hair has ever stood on end while unloading a clothes dryer, then you've felt the same force that drives an electrostatic loudspeaker (ESL).

An ESL is a push/pull motor powered by electrostatic attraction/repulsion.  The heart of the motor is a plastic diaphragm suspended between two conductive screens called stators.  A separate power supply puts a fixed DC bias voltage on the diaphragm, and the music output from an audio amplifier, routed thru a pair of step-up transformers, puts the driving AC voltages on the stators.  And the ultra-light diaphragm responds with instant precision to reproduce the music with exquisite fidelity.

The woofers and stat panels are controlled and powered separately using an active crossover upstream of a pair of stereo power amps.


The charges on the stators are dangerous. If the insulating coatings are not essentially perfect, touching both stators while the panel is playing could stop your heart.  Also, the high-voltage bias supplies should be enclosed within the speaker cabinets for safety. With children or pets in the home, protective speaker grills are a practical necessity. 

How it all began:
My fascination with ESL's started in 2006 when I auditioned a pair of Martin Logan Summits. Their phenomenal clarity and speed seduced me instantly but their price was light years beyond my meager budget. Like Gollum coveting the ring, I was ruined thereafter; not even wanting to power up my home system again... it was a dark time.

New hope came while browsing the DIY Audio Forum, where I found guys rolling their own electrostats for cheap.  So I got myself a copy of Roger Sanders’ Electrostatic Loudspeaker Design Cookbook and dived in.  After some weeks of study my hybrid design emerged, with a 10” woofer in a unique beam splitter transmission-line, and a 12"x 48" flat panel electrostat above the woofer.

Beam-Splitter Transmission Line ESL  - Original Version:

The Beam Splitter design:
Transmission line bass requires a huge woofer box, and the challenge was cramming all that volume into a small footprint and mating it to a tall stat panel-- all in a slim package.  Forming the woofer box into a V-shaped beam splitter allowed extending its volume upward, behind the stat panel, as the splitter deflects the panel's rearward sound out the open sides of the speaker rather than bouncing it back to the diaphragm.  

My criteria for a woofer with the speed to blend with the ultra-fast ESL are low QTS, low moving mass and above all a strong magnet coupled with a low-inductance voice coil.  I chose the Aurum Cantus AC250 MkII. 

The woofer is angled 8 degrees upward and couples to 9-foot transmission line.  Behind the woofer, the line transitions to vertical in a gentle curve that prevents resonances rebounding to the cone.

Power and Control:
Passive crossovers are not suited to an ESL's capacitive, frequency-dependent impedance so I recommend active crossovers exclusively.  Besides being superior an adjustable active crossover makes it easy to precisely balance the woofer and stat panel outputs in real time.     

My speakers are vertically bi-amped using a Behringer DCX2496 digital crossover feeding a pair of vintage Carver TFM25 power amps.  The crossover frequency is 220Hz via the 48db/octave Linkwitz-Riley filter.

The Moment of Truth:
I fired these babies up on July 4, 2008 with my goddess Diana Krall singing Nat King Cole's "You're looking at me". The illusion of Diana performing live in my living room was so spooky-real I could almost smell her perfume. Finally I have speakers worthy of Diana, who now sounds as good as she looks :-)

The electrostats are breathtaking and the bass is full and deep with gorgeous tone. In the second tune (“Peel Me a Grape”), the bassist does this wonderful riff with a long first note sliding upscale followed by two short notes stepping down, and down again, and the Aurum Cantus woofers were clean and tight, all the way down... it was just jaw-dropping.

Observations (original version):
The flat-panel electrostats are incredibly fast and detailed.  Even at very low volume, every nuance is heard and they can play ear- splitting loud with no loss of accuracy or hint of distress. They are, however, ultra-directional, with a sweet spot only about a foot wide; so, not a good choice for party speakers.  Within their focal sweet spot there is surreal imaging, exquisite detail, and stunning speed.  Moving out of the sweet spot, the beaming highs fall off progressively.  My friend Jason describes them as “remote headphones”.  A woman’s voice thru these speakers just takes your breath away.

A flat-panel ESL's beaming certainly constricts the sweet spot but this very characteristic projects a fully-coherent wavefront with practically none of the energy  bouncing off walls to interfere and confuse the imaging.  So while beaming may be a fault, the resulting sweet spot is magical indeed.    

Conclusion (original version):
No conventional speakers I’ve heard can match these for holographic imaging, clarity and speed. Not even the ML Summits can match their imaging. Moving outside the sweet spot, they are still clean and listenable but progressively less magical. Ultra-directional speakers don't suit everyone, but I live alone, so I'm free to hog the sweet spot, and I love their sound. Now, "everything else is two Dixie cups and a string".

Thank you:
Roger Sanders for your marvelous Cookbook.
Mark Rehorst and Sheldon Stokes for your inspirational DIY ESL websites.
GM at the DIY Audio forum for steering me away from my original, poor bass box design.  Calvin, Few, Jer and Bolserst at the DIY Audio Forum for sharing your knowledge with me.

Charlie Mimbs


My article in AudioXpress magazine:
(when the sign-up box opens, scroll down and click the
"free preview" link to open the magazine, then tab to page 14
to view my article)

Links to Photos & Build Instructions:
Building the ESL panels