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Old 7th January 2012, 11:14 PM   #1
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Default ESL woofer- anybody game?

I would like to build an ESL woofer that works below 200 Hz. I currently have ESL panels that work to that frequency and am using dynamic woofers. I think it could be better.
My initial inquiries have indicated much bigger spacing betwen the membrane and the stators, and very high voltages. Another problem seems to be the standoff voltage of the coating on the stators. Most panels use conventional powder coating processes, which seem to break down at about 2-3 Kv.
I have been told that Nylon is the better coating, but it appears to be very expensive.
Anyone out there game for this?
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Old 7th January 2012, 11:33 PM   #2
john65b is offline john65b  United States
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Why not buy a set of Magnepan Tympani Bass Panels? They are relatively inexpensive, a voice coil rewire isn't that hard, and no power is needed?
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Old 8th January 2012, 01:00 AM   #3
beun is offline beun  United States
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I am game, the most important questions are:

1) How large
2) Do we go double membrane like CLX, I did that already 30 years ago by the way on a headphone (still have that thing)
3) Do we use side ears to reduce front/back cancellation?

I don't think we need that large of a spacing 4-5mm should be more than enough as a 1m^2 membrane is capable of moving at least the same amount of air as a 15" subwoofer. The front/back cancellation in my opinion is the largest problem.
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Old 8th January 2012, 02:03 AM   #4
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I have been contemplating that for quite some time,
and I might have a drive system idea that might work.

But the one thing that I can tell you is you will need lots of surface area.
Displacement,Displacement,Displacement,Displacemen t !!!!

Compounded ( isobaric panels) may be the ticket to getting a controlled large excursion from such a system.
Otherwise your stuck with a D/S of not more than .125" to be practical.

One Idea that I have been tossing around since 2005 has been a AMT style ESL system.
I had just read through that thread again last night.
Bolserst did a great study touching on such a system and seems quite feasible but it will be very labor intensive process to build.

When you are talking about a dipole subwoofer system you need to move a lot of air to make it worth the while.

But I think that it is a great subject and is one of my many goals to try out.

Just a few of my thoughts on such a system.

jer

Last edited by geraldfryjr; 8th January 2012 at 02:05 AM.
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Old 8th January 2012, 04:02 AM   #5
beun is offline beun  United States
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A 15" woofer with a useful excursion of say 5mm can move 0.57 liters of air (please check my math). An ESL with 1m^2 area and say 2mm excursion can theoretically move 2 liters of air.

Since an ESL is supported at the edges and does not exhibit pistonic movement the amount of air moved is going to less than theoretical , say only 1 liter. This is still more than a regular woofer so in my opinion displacement is not the issue, the front/back cancellation is.

When a sub-woofer can move 10mm it is just equal to an ESL. with respect to air movement. A regular sub does have the advantage of a larger force.
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Old 8th January 2012, 05:00 AM   #6
gootee is offline gootee  United States
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The front/back cancellation won't be too bad, especially if you keep them far-enough from the wall (five feet or so). And angling them, relative to the wall, also helps, especially if it's the long wall. Some kind of "baffle" does help, too, especially along the "center" side of each speaker (at least in my room).

My little Magnepan MG-12s give me below 45 Hz, with only 369 sq in of mid-bass panel (according to Speaker differences , although my measurments say flat to below 40 Hz). And if I place something large up along the inside side of each one, and angle them just right, I can actually get too MUCH bass amplitude.

They are planar-magnetic, not electrostatic. But they are dipole panels so they should be comparable as far as the front/back cancellation effects are concerned.

As far as size goes, look at the link I gave, for what Magnepan was able to do with panels of various sizes. I don't know how it would correlate with size for an ESL, but it's something at least: It looks like they used 620 inČ a lot, to go down to 32 to 37 Hz. But then I see a 537 inČ that goes down to 34 Hz, too. And they have 786 inČ and 800 inČ models that go down to 25 Hz. Then again, they have a 1254 inČ that only goes to 30 Hz. Most or all of those that I just mentioned are bass-only panels, not mid-bass combined, like mine.

Last edited by gootee; 8th January 2012 at 05:13 AM.
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Old 8th January 2012, 05:36 AM   #7
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Yes I agree,
It is because of the front to back cancelations it takes much more displacement to make up the difference of that of a single driver in a monopole configuration can produce.
It is not really on issue of how low can you get it to go,But how loud for a given size.

For instance some examples of the 8' tall Acoustats can do the low frequencys rather well as there is alot of surface area.
But it was also stated that a subwoofer is still sometimes used as well.

Here are a few charts that I found while digging around in some old threads the other night that may be of some use.

And a zip file of two Linkwitz Labs Excel spreadsheets that I find most useful for determining ESL sizes and Dipole vs Monopole displacement per frequency and maximum SPL

jer
Attached Images
File Type: gif displacement chart regular.gif (34.4 KB, 499 views)
File Type: gif displacement chart metric.gif (28.8 KB, 492 views)
File Type: jpg acoustic_power_chart.jpg (70.4 KB, 492 views)
Attached Files
File Type: zip ESL XLS.zip (12.0 KB, 15 views)
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Old 8th January 2012, 12:36 PM   #8
tyu is offline tyu  United States
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I have now a pr of Acoustats M3 for 300hz down an a ML panels12"w by 48"L....an i still use what we call subs two ea.... 12" with there on amp.....my room is 18'w 25'L 14h....I am just playing with this setup....I use the subs with all my the speakers i have....If it Magnepans or ESls or all pistons....Two subs makes life so much ezer.....the Acoustat give good bass....but so big...the ML with the 10"pistons sound vary close....An i have done the Magnepan MG2cs, just for the 300Hhz down....for me... not sure it worth it..As for flat are crived ESL panels.... I think ML got it right... I like the sound of the flat for bass...crived for the highs...But the CLX only gos down to 55hz..subs are need
Good luck....Thanks for this post
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Old 8th January 2012, 06:12 PM   #9
Calvin is offline Calvin  Germany
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Hi,

Quote:
...and am using dynamic woofers. I think it could be better.
Yes, maybe, but certainly not with an ESL panel.
An ESL is no good bass!
...go to the black board and write this sentence down 100 times....

Try with dynamic bass drivers in dipole cabinets instead. Its easier and performs way better.

jauu
Calvin
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Old 8th January 2012, 09:34 PM   #10
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WOW! I hadn't expected this much interest! OK, some of my thoughts. Dynamic speakers, including Maggies have quite a bit of mass. Dipole dynamics have the box resnoance free response, but they have difficulty with tranients due to the cone mass, and it's the transient response that endears me to electrostatics.
Arnie Newdell (dale?) at Infinity used servo techniques to overcome this to an extent, but if I am not mistaken, he only servoed one driver in each array. Servos are also very tricky to build, and one minor misstep in tuning them can be disasterous.
Of course, the radiator would have to be large, and probably need side panels to reduce cancellations. For some of you, this aggravates the WAF.
Peter Walker of Quad fame used a "woofer" in the original design. Several things were at work- larger holes in the stators, greater membrane to stator distance, thicker membrane material with a different charge dissipation coating, and much higher voltages with commensurate higher ratios in the step-up transformer.
Some of you have mentioned some very intersting stuff, and I'm hoping you'll share your ideas more completely with us.
I'm hoping we can figure out and actually build some viable ESL woofs.
Thank you all for contributing
Jay
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