Another ESL Project

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Jazzman53

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Recently I built a hybrid ESL with an open baffle woofer for a friend. One of the requirements was that the speaker pair had to fit into my friend's 2008 Audi for transport, so boxed woofers wouldn't work. So I call this speaker design the "Audi". Below is a photo and HERE is a video of the new Audi speakers playing at the 2018 Carverfest retreat.

IMG_0906.jpg
 

tsmooth

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Video really gives you a feel for the design. How cool, the audio on your video sounded really good. What are your thoughts after hearing them? I believe there is an another member from the same area with an interest in ESL builds...(JonFo)
 

Jazzman53

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Video really gives you a feel for the design. How cool, the audio on your video sounded really good. What are your thoughts after hearing them? I believe there is an another member from the same area with an interest in ESL builds...(JonFo)
These were the prettiest speakers I’ve built—I hated to give them up. I only wish I had a pair to play around with them over time. I got to hear them for a week at Carverfest, though, and they were a big hit there. They do sound really good; especially the pristine mids and highs, dispersion is really good and trends very smoothly, the woofer and panel blend well, and they can play to ridiculous volume with no hint of distortion.

The segmented electrostat panel is a tried and true design (same configuration used in my personal ESLs) but the open baffle hybrid arrangement was a new thing for me, and this design build broke some rules:

The first rule being; never do a project with a friend (I won’t go into that further), the second being always base the design on a sonic goal (rather than the need to fit into my friend’s car), and the third being never use a low Qts woofer on an open baffle.

As for the woofer choice; in a hybrid ESL the woofer needs to play cleanly and have good transient response to a couple of octaves above the crossover frequency, or it won’t blend well with the ultra-fast ESL. This is why you don’t see any commercial ESLs using an OB woofer. But I figured a woofer optimized for OB, with its high-Q and a floppy suspension, would have no hope of tracking in phase with the ESL in the crossover band. For this reason, we opted for a low Qts woofer (normally used in a vented cabinet). Of course, this meant poor low-bass output, unless ton of EQ boost is applied.

As you may have noticed in the video, my friend has uses a pair of monster OB subs, and his setup is an actively tri-amp’d 3-way, with sharp filter slopes and the mid-bass woofer is chopped off sharply to the subs at 60Hz.

As designed, this hybrid ESL can’t do low bass with authority, but it has great mid-bass slam and it works just fine as a 3-way, with separate subs providing the bottom octaves.

I’ve heard that user name,‘JonFo’, somewhere in connection with DIY stats. There’s myself and a few others posting ESL build threads occasionally—I will look for him. A couple of real ESL gurus are Steve Bolser and Rod White (a.k.a. “Bolserst” and “Golfnut”) on the DIY Audio Forum. My latest designs would not have been possible without their advice.

Thanks for your compliment, sir :)
 

JonFo

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Hi Jazzman, congrats on another outstanding build!

Curious as to what step-up transformers you used, it looks like 2x Amplimo torodials per speaker.

Totally agree with you on the design constraint for the hybrid woofer, it must be able to play clean well above the x-over, so that generally means it can't do low-bass regardless of box topology, so subs are a must anyway.

And while I dable in ESL mods, I've never actually built an ESL panel like you have. I just 'system engineer' around existing ML ESL components, best example is my center channel the SL3XC. What I have gotten proficient at is tuning active crossovers ;)

Anytime you are in Atlanta, or least north of town (Big Canoe is 1 hr north of Alpharetta), feel free to contact me and I'd be happy to give you a demo of my rig.
 

Jazzman53

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Hi Jazzman, congrats on another outstanding build!

Curious as to what step-up transformers you used, it looks like 2x Amplimo torodials per speaker.

Totally agree with you on the design constraint for the hybrid woofer, it must be able to play clean well above the x-over, so that generally means it can't do low-bass regardless of box topology, so subs are a must anyway.

And while I dable in ESL mods, I've never actually built an ESL panel like you have. I just 'system engineer' around existing ML ESL components, best example is my center channel the SL3XC. What I have gotten proficient at is tuning active crossovers ;)

Anytime you are in Atlanta, or least north of town (Big Canoe is 1 hr north of Alpharetta), feel free to contact me and I'd be happy to give you a demo of my rig.
Hi Jonathan,

If I get up your way I will PM you first and take you up on your offer. Likewise if you're ever in Savannah I would love to have you drop in.

Actually, those transformers are standard European 50VA 230V/2x6V toroidal power transformers.
Not quite as good as the ($$$$) Aplimo's but almost, and they only cost $20 each! A pair of them wired with their 6V windings in parallel on the input side and their 230V windings in series on the output side gives a 76:1 voltage step up--- perfect for a hybrid panel and they sound great. Very popular DIY option.

My first pair of DIY ESLs (2008) used perf metal stators and 100:1 IE core audio transformers designed for ESLs (about $250). They sounded pretty good but I'm a bit treble deaf and the highs weren't blowing my skirt up so I decided on a whim to try the cheap toroid option. The much-cheaper toroids blew the audio transformers away (really good highs now) and I think they are more robust to boot.

Charlie
 
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