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Old 7th October 2013, 01:43 AM   #21
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Quote:
Originally Posted by bear View Post
Just to throw some tomatoes into the mix...
...one word: Beveridge.
What? You drinkin' Bloody Marys tonight or what?

I'm havin' a few 'Beveridges' myself tonight...

(Actually, I have no idea what you're talking about...haha)

I was digging around in the McNichols catalog a few days ago and found some 63% open perf sheets (18 gauge) that were $155 for a sheet 36" by 120". I asked for a quote to ship it to me cut in 4, and they gave me a price of $230...WTF? That's not including the $20 shipping and handling... Really? You guys want that much to set it up? Yikes!

I looked up gauges in inches on Wiki and it says that 18 gauge is .05 inches, then I looked up 20 gauge and that stuff is .0375 inches, but at a cheaper price ($112), so I imagine that 20 gauge would be about $190 or so, much better.

That is if 20 gauge is going to be OK for ESL construction.

If I plan on using a fair amount of paint/powder/insulation, do you guys think 20 gauge would be OK?

It looks a lot like MLs X-stat perf, only not quite as open, but real close.

I attaches a couple of pics for visual reference below:

Just another question in a long line of other questions...

cheers
-wreck
Attached Images
File Type: jpg 5-32 on 3-16 centers staggered.jpg (962.7 KB, 261 views)
File Type: jpg ML X-stat.jpg (96.7 KB, 254 views)
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Old 7th October 2013, 10:14 AM   #22
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Beveridge...I have seen the light..lol
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Old 7th October 2013, 12:50 PM   #23
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You want HF dispersion, right? That's one way to do it.

Might be fairly simple to improve upon that now old design...
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Old 7th October 2013, 07:57 PM   #24
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Sorry for hijacking the thread a bit, but I find the discussion about ESL panel size and SPL interesting. I have a pair of Acoustat Spectra 11's as mains right now and I feel like the SPL is enough at about 8 feet listening distance (my room is about 180 sqf). For the lower frequencies I'm building a OB bass tower similar to Calvin's designs (thanks for the help Calvin ).

I've considered replacing the Acoustat with a smaller and more modern design like the ER Audio Mini Panels (they are currently redesigning them to be a bit slimmer and taller, and add vertical segmentation for better HF dispersion). What would be compromises in terms of sound quality and SPL be? To calculate how much air a dynamic driver is moving you can simply multiple Xmax with the surface area. Is it the same for an ESL panel and what is typically "Xmax" for a panel? Does the transformers limit the SPL of the panel?

Thanks.
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Old 7th October 2013, 08:48 PM   #25
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phazer99, at $410 a panel, I think you're better off staying with what you have.

Otoh, you can build your own ESLs anyway you like. Looks like the same outfit sells the important and difficult to find "stuff" for building ESL cells.

In ESLs, all things being equal, more surface area = more SPL, and usually more bass output (not necessarily LOWER bass though, but probably so since baffle width plays a big role.
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Old 7th October 2013, 11:50 PM   #26
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Quote:
Originally Posted by bear View Post
You want HF dispersion, right? That's one way to do it.
Reason why I wouldn't is in my first post in this thread, the wall vs window argument.


Quote:
Originally Posted by bear View Post
Might be fairly simple to improve upon that now old design...
I didn't even know Beveridge existed until this morning, looks like the curve I put on this tweeter way back in '99, my first DIY on a pair of Scan-Speak drivers. (see attachment)

@ Phaser, Not a big derail, no worries.

Forgot to mention that the McNichols perf I posted last night has 5/32" holes on 3/16" centers, are those considered too big? Enough to negatively affect field density? If anyone knows or has an opinion, please respond, thanks.

Off topic: I saw this thread while I was at work today but couldn't respond because I was on my Android phone, does anyone know if there is an app for doing this?

thanks
-wreck
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Old 8th October 2013, 12:26 AM   #27
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Ok, either you or I are rather confused?

Quote:
I own flat ESLs that are 14.5 inches by 42 inches that sit atop my (10 inch Peerless) 8 foot long tapered DIY transmission line. Now I love my t-lines, but my ESL stators are getting rusty, and most importantly, I am looking to get away from having my head in a vice just to enjoy the listening position.
Sounds like you want horizontal dispersion? No??

You said you wanted "curved" panels, right? The purpose of the curve is dispersion, yes?

Flat panels are not going to have good HF horizontal dispersion unless either exceptionally good segmentation is employed (frequency as in Acoustat Spectra, or time as in ESL63) or an acoustic lens is used (Beveridge). There are not too many other choices.

Oh, wait, I just re-read you post and your saying that the curve on the tweeter you built is like the Beveridge. No, it's not in
any way close. Best read up a bit more on the Beveridge design. While it is *not* precisely what you are going for, it does
represent a means by which "curvature" can be produced by a flat diaphragm speaker. It's *not* a curved box that is important to the Beveridge design.
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Last edited by bear; 8th October 2013 at 12:33 AM.
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Old 8th October 2013, 02:45 AM   #28
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Quote:
Originally Posted by bear View Post
Ok, either you or I are rather confused?
Leaving this alone, I stated I'm a 'beginner' earlier in this thread.

Quote:
Sounds like you want horizontal dispersion? No??
Yes, I want horizontal dispersion, preferably with an ESL panel. I read in Sanders cookbook that if had a 30 degree curve on my ESLs, at 10 feet away, I'd have 5'7" horizontal dispersion, then I extrapolated that figuring (into) using 2 panels, and that intrigued me as well. That was the main point of me starting this thread.


Quote:
You said you wanted "curved" panels, right? The purpose of the curve is dispersion, yes?
Only if it works as advertized, even if it doesn't, and say it only provides half of that performance, I'm still intrigued.

Quote:
Flat panels are not going to have good HF horizontal dispersion unless either exceptionally good segmentation is employed (frequency as in Acoustat Spectra, or time as in ESL63) or an acoustic lens is used (Beveridge). There are not too many other choices.
My flats certainly don't give good HF-HD, I was under no illusion that flats did, I own them, I know.. You guys keep mentioning segmentation, got links? (or explanations etc.)


Quote:
Oh, wait, I just re-read you post and your saying that the curve on the tweeter you built is like the Beveridge. No, it's not in
any way close. Best read up a bit more on the Beveridge design. While it is *not* precisely what you are going for, it does
represent a means by which "curvature" can be produced by a flat diaphragm speaker. It's *not* a curved box that is important to the Beveridge design.
I merely took a quick look at some Beveridge images, and if you re-read my post, I said it looks like my old DIY project, nothing more.

Upon re-observation of this thread, seems that many have thought my proposed panels are too wide. Am I using incorrect equations when it comes to this? I figured 200 Hz quarter wavelength was around 16 (point something )inches... and that if I want to avoid dipole phase cancellation, I'd pick a width nothing short.

The last thing I want to do is artificially dope my ESLs with a FR it can't handle, it's artificial.
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Old 8th October 2013, 02:47 AM   #29
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Hi,

hass it been veryfied, that such a lens performs as claimed?
Recently a guy showed his built in the german Elektrostaten-Forum.
It was similar to the Beveridge lens, made from thin plywood, with a lower number count of slots.
Unfortunately he couldn't measure to verify the claims for such a lens, resp. simplified lens.
I assume that the effect will be lower than expected, the same as the degree of a curved panel doesn't equal the degree of dispersion.
Can one be sure that the lens itself doesn't effect the sound with its own acoustic fingerprint through reflections, resonating et al?

jauu
Calvin

Last edited by Calvin; 8th October 2013 at 02:50 AM.
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Old 8th October 2013, 08:24 AM   #30
Calvin is offline Calvin  Germany
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Hi,

Quote:
3/8" or 3/16" is not a question, but the road to hell.
I meant, that 3/8" will make a noteable difference to 3/16" and that either this or that is not debatable, as design requirements for an optimum design will immideately dictate the right choice.

Quote:
You also mentioned insulating making my hair gray, could you expand on that too? I would appreciate it.
Well, I guess You are eagerly reading papers, threads and books at the time.
So I won´t spoil the fun of finding out who´s the murderer. Sure You´ll soon find out the answer.
But I could pluck out some of my spare gray hair and mail it to You

It seems since #8 to be an upcoming idea, that to increase SPL one could just crank up signal and biasing voltages and make the panel larger.
While this works at first glance on paper there are limits and restrictions in practise.
Biasing and Signal voltage regard the achievable force on the diaphragm.
This is eventually limited by the flashover voltage of air, typically quoted to be ~2kV/mm. 1.5/mm to 1.7kV/mm is a more practical value to provide for a truly quiet panel under different air conditions.
Now, as Gerald said in #8 You do the math for 0.075", 6kV bias and 20-25kVpp signal.
Under perfect conditions a 0.075" airgap would allow for 3.8kV Bias before the flashover treshold is reached.
This Bias value allows for 7.6kVpp signal, before signal frequency doubling occurs. Obviously much lower values.
Since I trust him even with those bold claims, the only explanation I have is, that between the measurement points and diaphragm a great deal of the voltages must have ´disappeared´.
This could be in form of too high valued resistors in the biasing path, massive leakage, or due to a very lossy insulative coating of the stators. In the latter case, it might have been of interest to measure, if a temperature rise occured

Since most panels electronics will be designed already close to the voltage tresholds the panel allows for, the most promising way to increase SPL is to size up the panel.
The problem here beeing that a larger panel also requires larger listening distances, proportional to the increasing nearfield-to-farfield transistion distance.

As for the amount of eq against acoustic phasecancellation, wider panels would require less dBs at a certain low xover frequency.
But again one has to watch for the relationships. Changing just one parameter, changes several other related parameters as well.
Typically the larger/wider panel will be designed to achieve a lower bandwidth limit.
This regards the distances of spacers, the thickness of spacers (d/s), mechanical diaphragm tension, bias and signal voltages, transformation factor, etc. etc.
For highest efficiency and dynamic stability the diaphragm needs to be pulled as taut as possible.
Depending on membrane type and thickness this will result in a base resonance 120Hz<Fs<250Hz. If You keep off of Fs by at least a factor of 1.5 You´ll end up with Xover-freqs of 200<Fxo<400Hz. The difference in equing between the panels is not so big any more that it plays a deciding role.
You can always fudge a bit and add wings to the panel sides, thereby ´passively´ increasing baffle width.
The high mechanical tension requires a solid fixation of the diaphragm in the vertical direction. I´d choose at least 1" of non-perforated rim here.
The vertical rims may be thinner as there´s nearly no mechanical tension in the horizontal. 1/2" is a good choice as it is wider than a charging ring, which is positioned around the perimeter also for high flashover treshold and nice optics.

Regarding different spacer thicknesses front/back stator, it is a con in theory, but can be a pro in practise.
It doesn´t necessarily increase asymmetry, but actually helps in increasing symmetry (low THD) and dynamic range.
It counters to a degree the unavoidable tendency of the diaphragm towards a hour-glass shape due to manufacturing tolerances.
A difference of ~10% is perfectly practical.

The 5/32" to 3/16" pattern is a good choice. If the perimeter is perforated also, You have to treat the rims, such that no sharp edges remain, which are prone to flashovers.

jauu
Calvin
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