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Old 19th June 2014, 02:21 AM   #11
EStat is offline EStat  United States
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Quote:
Originally Posted by bolserst View Post
@bentoronto,
Any idea on the total area and excursion capability of your Dayton-Wright ESLs?
Pardon the intrusion, but I can answer part of your question. And the answer derives differently from any other electrostat (among many) that I have experienced. As for area, there are two answers. Huh? The Dayton-Wright design employed either eight or ten panels (four or five stacked) in the cabinet. Attached is a pic of a later ten panel XG-10 version.

What you may not notice is there are two diaphragms. The one on the panel and the second one that covers the entire surface of the cabinet. Why? The design incorporates the usage of sulphur hexafluoride gas to lower the resonance and provide additional power handling. In other words, the panels lived in a box sealed with another mylar diaphragm filled with electrical insulating gas. Consequently, the radiating area for bass response is that of the outer diaphragm, not the sum of the multiple panels. The answer is about nine square feet. If you're interested, here's a link to a more comprehensive description.

SF6 gas exhibits the opposite characteristics of helium being heavier than air. If you put some of the gas into a cup, it would settle at the bottom, but it was colorless. If you put your finger in the cup, you could feel the gas present. I was present when a reviewer friend replaced a panel. That process necessarily meant puncturing the outer diaphragm as the initial step. After replacing the panel proper, the outer mylar was sealed using mylar packing tape and the cabinet was re-pressurized with SF6 gas. The funny part is my friend is a baritone in a major city symphony chorus. He sung part from an operatic piece that sounded like Lurch at The Met.

The Dayton-Wright was an incredible design that incorporated truly unique aspects. Unfortunately, it suffered a bit in response at the lowest and upper most octaves. But what it did was simply glorious. Nelson Pass demoed his Threshold amplifiers in the early 90s using a stacked pair of double Daytons - which have the radiating area of the larger current Sound Lab stats.
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Old 19th June 2014, 06:22 PM   #12
SyBorg is offline SyBorg  United States
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Bolserst, Maybe this is a dumb question and will only further establish my ignorance in this area... When you speak of resistive damping, are you referring to an electrical compensation (i.e. a resistor along with the inductance of the transformer and capacitance of the panel) or a physical damping material on the stators or diaphragm?
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Old 19th June 2014, 07:33 PM   #13
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Quote:
Originally Posted by SyBorg View Post
When you speak of resistive damping, are you referring to an electrical compensation (i.e. a resistor along with the inductance of the transformer and capacitance of the panel) or a physical damping material on the stators or diaphragm?
Sorry for the ambiguity
I should have said resistive acoustic damping.
Usually this is in the form of a fine cloth mesh or felt attached to the stator.
In case of the Quad ESL-63 it is a fine silk screen mesh attached to the inside of the rear stator.

For more details on effects of acoustic damping, see the first link in post#3 on the subject.
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Old 19th June 2014, 08:14 PM   #14
EStat is offline EStat  United States
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Originally Posted by bolserst View Post
For more details on effects of acoustic damping, see the first link in post#3 on the subject.
And note that Dr. West of Sound Lab takes a different approach from the methods you mentioned.

The panel facets vary in height from top to bottom to distribute the inherent diaphragm resonance.

Distributed Resonance details
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Old 20th June 2014, 11:05 AM   #15
Calvin is offline Calvin  Germany
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Hi,

after my tests the dimensions of the segments must differ considerably, hence theirīs Fs must differ considerably, to give an noticeable spread and reduction of the combined Fs.
Also, the segment with the lowest Fs will determine the maximum output, thereby sacrificing on efficiency.
As so often the "revolutionary patented principle" works on paper much better than in reality.
The outrageous claims are mainly marketing-BS.
The base drumhead resonance is not īkilledī but just slightly broadend, and the acoustic phase cancellation still takes place, itīs effect also just slightly reduced.
If the principle functioned as claimed, the anyhow low efficiency of the panel would drop into the cellar for the low bass.
As efficiency is the most prominent parameter for a good ESL design, draw Your own conclusion

There are only two measurements against that problem:
1) electronic equalisation - most precise, doesnīt really counter the long decay on the panelīs Fs
2) (frequency dependant) resistive damping - not very precise, nearly impossible to achieve the desired frequency dependance, counters the long decay quite well

The second point is what Bolserst described and tested.
The silkscreen mesh obviously introduces a considerable amount of LF-damping and seems acoustically transparent at higher frequencies.

jauu
Calvin
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Old 20th June 2014, 02:01 PM   #16
EStat is offline EStat  United States
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Originally Posted by Calvin View Post
As efficiency is the most prominent parameter for a good ESL design, draw Your own conclusion.
I arrive at a different conclusion since the most important parameter to me is audible performance. Theory works only to a point.

That includes: high resolution, wide bandwidth, and controlled directivity over a wide area. Two hundred watt amps drive SLs quite well.
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Old 22nd June 2014, 09:55 PM   #17
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Quote:
Originally Posted by Calvin View Post
after my tests the dimensions of the segments must differ considerably, hence theirīs Fs must differ considerably, to give an noticeable spread and reduction of the combined Fs....The base drumhead resonance is not īkilledī but just slightly broadend, and the acoustic phase cancellation still takes place, itīs effect also just slightly reduced.
With 12 incremental section sizes, the SL A-1 shows a spread of resonance frequencies of a bit over an octave. You are correct that the resonance is not ‘killed’, rather each section has its response broadened and usefully lowered in Q to somewhere between 2(small sections) and 5(big sections). The resulting overlays are a visual mess and it seems unlikely that a desirable bass response would result. But, measured response at the listening position is flat in the bottom two octaves. As Estat mentioned, the audible performance is surprisingly good…especially after seeing the measurements. Plucked and bowed string bass is reproduced well, which usually gives FR ESLs with high-Q resonances fits. (Audiostatics are a perfect example of this)

Quote:
Also, the segment with the lowest Fs will determine the maximum output, thereby sacrificing on efficiency.
This is one of the things that troubles the engineer in me about the distributed resonance technique. For example, between 25Hz-35Hz, less than 1/3 of the total panel area is producing useful output. For constant SPL, volume displacement needs to increase by a factor of 8 each time frequency is halved below the dipole cancellation frequency. With only 1/3 of the panel area producing at the lowest frequencies, the D/S spacing must be increased substantially to allow the required diaphragm motion needed when only 1/3 of the panel area is used. This in turn requires increasing the bias voltage and transformer step-up ratios to keep efficiency at a useful level. I much prefer using a single resonance frequency and acoustic damping. This ensures the entire panel area provides useful output at the lower bandwidth limit. This allows the use of smaller area panels and lower D/S spacing for the same SPL output.

Note also that the improvement in LF output from resonance is not enough to completely equalize the roll off due to dipole cancellation. SL uses a similar setup to Acoustat where the output from a LF transformer with a higher step-up ratio is mixed with the output from a HF transformer.
Example SL interface circuit posted here:
Acoustat MK series.
Example Acoustat mixer response posted here(SL is very similar):
Open CLS II stators - the best way to do it?

Quote:
Originally Posted by EStat View Post
Dr. West of Sound Lab takes a different approach from the methods you mentioned.
Note that the Sound Lab patent claims on distributed resonance were cancelled in 1994 when the patent was rexamined. See the last page of patent US5054081.

Perhaps it was discovered that Magnepan's 1972 patent (US3674946) already taught the technique of distributed resonance for planar ribbons. See Figure 12 & 13 for details of diaphragm sectioning and resulting distributed resonances. Applying the concept to ESLs, perhaps, was not deemed novel enough to warrant a patent.

If interested, I had previously posted these patents here:
ESL woofer- anybody game?
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Last edited by bolserst; 22nd June 2014 at 10:22 PM.
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Old 22nd June 2014, 10:14 PM   #18
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Quote:
Originally Posted by EStat View Post
The Dayton-Wright was an incredible design that incorporated truly unique aspects. Unfortunately, it suffered a bit in response at the lowest and upper most octaves. But what it did was simply glorious. Nelson Pass demoed his Threshold amplifiers in the early 90s using a stacked pair of double Daytons - which have the radiating area of the larger current Sound Lab stats.
Thanks for sharing your experience with the DW ESLs...not a whole lot of first hand info out there.
After passing of my senior moment, I remembered that bentoronto had already posted measurements and particulars on his DWs several years ago.
Dayton-Wright XG-10


Quote:
Originally Posted by bentoronto View Post
Minor note: I am puzzled why the later DW need the tweeters. Earlier models had a fine treble, I believe.
As best I can tell by reading through the DW literature on the website Estat linked to, the tweeters were added because the later transformers were limited in their upper bandwidth. Basically they had to make a compromise between LF capability, HF limit, and efficiency. LF capability drives increased primary turns, efficiency drives increased step-up ratio, both of which work against the HF limit.

Last edited by bolserst; 22nd June 2014 at 10:24 PM.
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Old 23rd June 2014, 12:33 AM   #19
EStat is offline EStat  United States
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Originally Posted by bolserst View Post
With 12 incremental section sizes, the SL A-1 shows a spread of resonance frequencies of a bit over an octave. You are correct that the resonance is not ‘killed’, rather each section has its response broadened and usefully lowered in Q to somewhere between 2(small sections) and 5(big sections). The resulting overlays are a visual mess and it seems unlikely that a desirable bass response would result. But, measured response at the listening position is flat in the bottom two octaves. As Estat mentioned, the audible performance is surprisingly good…especially after seeing the measurements.
Actually, I measured over three octaves because most bass non-linearity occurs there. They were performed at the listening position (about 8'- since I do very little listening an inch away). If you're interested, my third octave plot is linked below. Surely a RTA plot would be more ragged, but not wildly so. I will be the first to admit, however, that did not *magically* occur by simply plopping them in the room. I spent considerable time experimenting with three variables: distance to back wall, arrangement of bass traps and bass contour setting on backplate (there are four settings in 3 db increments).

In room response curve

Click the image to open in full size.

Quote:
Originally Posted by bolserst View Post
Plucked and bowed string bass is reproduced well, which usually gives FR ESLs with high-Q resonances fits. (Audiostatics are a perfect example of this)
The audible result is dead neural tonal balance and exceptional detailing of first and second octave bass. You can easily hear the character of synthesized bass and concert drum

Quote:
Originally Posted by bolserst View Post
This in turn requires increasing the bias voltage and transformer step-up ratios to keep efficiency at a useful level. I much prefer using a single resonance frequency and acoustic damping.
While the approach seems more elegant than throwing a blanket on the panels, I'm not particularly attached to any one approach so long as you get linear results. Speaking of bias, the Sound Lab backplate offers a variable bias control. This allows you to optimize the drive for varying humidity as well. Where the Acoustat interface ran at 5 kV (if memory serves), the SL backplate is adjustable to 12 kV - SF6 unnecessary. You increase the level until you hear crackling and back down. Another reason this design requires high bias is the diaphragms are incredibly low in mass.

One of the great things about the Acoustat panel design is its infamous ruggedness. My 1+1s are pushing thirty years old and many are older. This is no doubt a testament to a solid design - but also the rugged nature of using relatively thick diaphragms - 17 microns. By comparison, the original Quad ESL 57 used 12 micron bass panels and 6 micron tweeter panels. The current single panel Quads are 3 microns and Sound Labs uses 2.5 micron material. Like sandwich wrap.

Quote:
Originally Posted by bolserst View Post
SL uses a similar setup to Acoustat where the output from a LF transformer with a higher step-up ratio is mixed with the output from a HF transformer.
Yes, indeed. A critical difference, however, is the Sound Lab design uses toroidal trannies. The advantage that Acoustat and Sound Lab have over single transformer designs is a more linear and gradual impedance curve. That allows the use of tube amps in the mix (which I prefer). Look at a plot of a Quad, Innersound, etc. curve at Stereophile and its looks like a roller coaster.

Quote:
Originally Posted by bolserst View Post
Note that the Sound Lab patent claims on distributed resonance were cancelled in 1994 when the patent was rexamined. See the last page of patent US5054081.
No doubt that marketing always creeps into the selling of most products.

What I find most beneficial from Dr. West's approach has to do with virtually eliminating the head-in-a-vise imaging challenge shared by most stats. As an owner of 1,2,3 and 4 across Acoustats, the problem grew worse when more panels were added. You got increased efficiency and better bass response (good), but the sweet spot was two inches wide with the wider versions. With my 2+2s, I literally used a laser pointer and string from panel to my head to optimize placement. While the Spectra approach of turning the system into effectively a two way by limiting HF content to half of one panel minimized that issue, if you were off axis to the tweeter panel section, the tonal balance changed. Using multiple facets aimed at differing angles provides a far wider pattern of directivity. On my three person couch, those to either end hear a different column of facets than the center seat.

Another advantage to maintaining a true full range approach (as opposed to literal or virtual tweeters) is that they are scalable. When I visited the Sound Lab manufacturing facility following a panel upgrade, I was shown a picture of a large array of Prostats used in an auditorium in Utah. Each channel was comprised of five 9 foot by forty inch 22 degree panels - stacked for a total of ten per side. The array provided 18 foot tall vertical coverage across a 100 degree plus horizontal dispersion.

Last edited by EStat; 23rd June 2014 at 12:52 AM.
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Old 23rd June 2014, 12:40 AM   #20
EStat is offline EStat  United States
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Originally Posted by bolserst View Post
Thanks for sharing your experience with the DW ESLs...not a whole lot of first hand info out there.
I will always have fond memories of Dayton-Wrights. In addition to extensive auditioning of the MKI panels of my reviewer friend, the owner of the shop where I worked in college had MK3s at home driven by Threshold amplifiers - first with an 800A and later, with a Stasis 2. Both JWC and Julian introduced me to quite a bit of classical music in my teens and early 20s.

It was because of those positive experiences that I purchased a Stasis 3 in 1981 that I still use to this day with the Acoustat 1+1s in the garage system. It has continued to provide utterly reliable service aside from a proactive replacement of the big Mallory computer grade power supply electrolytics. If you like pics, click here.
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