Yet Another Hybrid ESL Project

Hi all,

Since October of last year I've been toiling away on my biggest-ever ESL speaker project. And in the coming weeks I will be posting some photos as the project nears completion.

Several of my Carver Audio friends have twisted my arm for years to build speakers for them, but until now I've resisted because my designs are exceedingly tedious and exhausting builds, especially for an old guy like me. My friends chose my lightweight Audi speaker because it's more transportable than my other, heavier designs. I must have bumped my head somewhere because I finally agreed to do it.

I'm about 85% thru building four (4) pairs of a similar OB hybrid speaker that uses a 12" woofer mounted on a semi H-baffle. The frames are red oak and the stat panels are electrically segmented to emulate a line source projecting a cylindrical wavefront. This is accomplished using stators with frequency and phased-array wire groups driving the diaphragm sequentially from the center-line outward. The stator wires are 20 AWG, UL-1061 SRPVC insulated, single-strand copper.

The new speakers are a refined version of the Audi speaker shown in the video below. Refinements include a slightly narrower dispersion pattern for more precise imaging, a new 3.2kV bias supply assembled on a dedicated PC board rather than a prototype perf board, a slightly slimmer depth frame, and magnetically attached grills front and back. I will also be testing a couple of different woofer options.

Building eight speakers (four pairs) at once has been exhausting but I think the sonics and aesthetics of will be a cut above.

The video below shows the original Audi speaker built in 2018, along with my method of building the wire stators for the new speakers. I will follow up soon with another video showing the diaphragms being tensioned and the panels being assembled.

More to come, but for now; enjoy the video and photos below!

 

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microstrip

VIP/Donor
May 30, 2010
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Great project - it seems you are building the linear ESL63! What type of coating are you using on the mylar?
 
Great project - it seems you are building the linear ESL63! What type of coating are you using on the mylar?

Yes! That's a great analogy with the 63.

For coating the diaphragm; I use Licron Crystal ESD, which is a spray on product that puts an static dissipative coating on plastics. It dries to about 2 microns thickness with E7-E9 resistance. I've been using it for about 10 years now. It's not cheap ($50 for an 8-oz rattle can) but it's an excellent, reliable coating for ESLs-- much better than graphite.
 

Kcin

Well-Known Member
Mar 27, 2016
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Wow, just fantastic craftsmanship. You should be very proud of your work.

Congratulations!
 

MRJAZZ

[Industry Expert]
Jan 21, 2014
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Excellent work.....
 

HughP3

VIP/Donor
Apr 25, 2019
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Amazing work. I had Maggie 20.7 and the working physics of sound through them is mysterious to me. Are you self taught or a EE?
 
Amazing work. I had Maggie 20.7 and the working physics of sound through them is mysterious to me. Are you self taught or a EE?

The Maggies are fine speakers; although they use a different drive principle than electrostats.

I have no education beyond high school so; self taught. I've had a lot of help over the years from the online community of ESL builders that post on the DIY Audio Forum, planar section. There's even an Excel spreadsheet program created by a couple of very smart guys on that forum, which I used to configure the wire segmentation scheme in my speakers.

You can find more info and build pics for all of my projects on my website here:
http://jazzman-esl-page.blogspot.com/
 

HughP3

VIP/Donor
Apr 25, 2019
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The Maggies are fine speakers; although they use a different drive principle than electrostats.

I have no education beyond high school so; self taught. I've had a lot of help over the years from the online community of ESL builders that post on the DIY Audio Forum, planar section. There's even an Excel spreadsheet program created by a couple of very smart guys on that forum, which I used to configure the wire segmentation scheme in my speakers.

You can find more info and build pics for all of my projects on my website here:
http://jazzman-esl-page.blogspot.com/

Thanks JM. I admire your skill. Did you design the cool jigs? In any event you wood working looks perfect. Your recipients should be very grateful!
 
Thanks JM. I admire your skill. Did you design the cool jigs? In any event you wood working looks perfect. Your recipients should be very grateful!

Yes, I think I spent more effort designing that stator jig that I did designing the speaker, lol.

The project is coming along.. all the panels are built and now soldering up the segmentation networks, and then I will do the grill covers. These will be the prettiest speakers I've ever built. I a couple of days I will post a video showing the diaphragm tensioning and panel assembly.
 
Update Tuesday evening, March 3:

The speaker frames have been completed for weeks.
I've just completed assembling all eight ESL panels.
I'm about halfway thru assembling the (16) segmentation resistor networks.
Still have to buy the woofers and build the magnetically attached grills.

I just posted this Youtube video showing the diaphragms being installed and the panels assembled:
 

HughP3

VIP/Donor
Apr 25, 2019
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I really enjoyed that. Thank you!
 
Today I got "first sound". That is; I completed and played one pair of speakers today. I have to order the woofers for the other three pairs. On the pair I finished today I'm using Peerless SLS 12's and my fist impression says these inexpensive woofers are going to work fine. At the moment I still have the system in 3-way mode triamp'd with Ripole subs. For info purposes only; I will also run the SLS woofers in a 2-way configuration without subs, just to see how well they perform.

I still have to purchase and install woofers in the remaining three pairs, and then build the grills but I'm happy that this project is wrapping up after 5 months of toil.

Below is a photo and video made today:

 

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ack

VIP/Donor & WBF Founding Member
May 6, 2010
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Really really impressive! Bravo!
 

Vienna

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Oct 14, 2018
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Indeed nice
 

ack

VIP/Donor & WBF Founding Member
May 6, 2010
6,783
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580
Boston, MA
That video from March 3rd is just incredible!
 
Update 3/23/20:

All four pairs of speakers are fully completed except for the magnetically attached grills, which I started building today.

I spent the weekend sound testing every pair, and they all play to ridiculous volume with no apparent issues. For a $77 woofer; I'm pretty impressed with the Peerless SLS-- I was concerned it wouldn't be up to the task so I only ordered one pair initially. I should point out that so far I've only sound tested them chopped off at 60Hz and crossing into a pair of Ripol subs with a 24db filter slope. Thus unloaded on the bottom end; the Peerless woofers rock pretty well without bottoming out at X-max.

Parts Express had the black grill cloth but not the burgundy I want for my pair-- so I was happy to finally locate some 66" x 36" sections on Ebay. That order arrived today and it's only 54" x 36". With the Corona virus lurking and me old as dirt, I'd rather lose the refund than risk the post office to return a package.

Just one more delay in wrapping this project up...

In the meantime-- more porn for the planar pervs:
 

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Update 3/26/20:

Having a lot of problems with the grill frames. They looked great the day I built them but they bowed after a couple of days and I'm having to redo them. The first time I used white pine stiffeners on the hardboard frames, the second time I used poplar. Both bowed but the poplar bowed a bit less. So I'm cutting the stiffeners off and bonding new stiffeners on with the frames purposely bowed in the opposite direction, hoping they will bow back to near straight condition. I may end up giving them a week or so to stabilize, then cross cutting slots in the vertical stiffeners to relived the bow, and then gluing on some strips to re-stabilize. They will look nice if I can resolve the bowing issue:
 

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Hi all,

This project (all four speaker pairs) is finally completed, so this will be my last post on this thread unless it's in response to others.

I resolved the issue with the grill covers bowing and they turned out gorgeous.

I finally now have my dream speakers for life, and I'm sure the recipients of the other three pairs will feel the same way.

I'll just leave you with a last video of the speakers playing:

 

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