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Old 25th December 2008, 08:00 AM   #11
Calvin is offline Calvin  Germany
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Hi,

of course is it not my habit to insult people. I always try to answer in a precise and correct way, but if I take my time and put effort into answering to a stranger┤s question its done in the hope, that the answer helps. To realize that the effort was in vain, because it wasn┤t read carefully, let alone understood, is rather disappointing and discouraging. Disappointing, because it shows that I have to improve a lot on my English, discouraging, because were those sentences -just for example- really not understandable??
Quote:
A grounded safety grid could be a possible solution, but it needs an extra wire for earth connection. As far as I know no commercial design did that. ...Each capsule is wired by a three-wire-cord to the supply, hence, there is no PE-wire leading to the HP.
jauu
Calvin

ps: sorry for not answering Your other Qs, but I need to work on my ┤hard to decipher┤ English.
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Old 25th December 2008, 09:08 AM   #12
Lucius is offline Lucius  United States
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Default Shocking!

What will it be, a hair net or a piece of coal for X-Mass?
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Old 25th December 2008, 11:56 PM   #13
j beede is offline j beede  United States
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I suppose the worst case with floating (i.e. ac coupled) shields would be a static discharge-assuming that the shield is adequately isolated, mechanically, from the stators. It would be preferred to avoid grounding the shields for at least two reasons: avoid the extra conductor in the cord and eliminate the risk of injury when the ground path is interrupted. Okay, floating screens it is.
...j
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Old 26th December 2008, 04:39 PM   #14
j beede is offline j beede  United States
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Quote:
Originally posted by chinsettawong



The holes are 2 mm and the hole to hole spacing is 2mm. I do not know the total open area, but they do really sound wonderful.

Wachara C.

Hello Wachara C.
That means that from center-to-center your holes measure 4mm? I am using 1.6mm holes that are 3.2mm, center-to-center. That happened to be the type of perforated sheet steel I had available. My next set of stators will use the same size holes, but closer together. My stators are very rigid and thinner material with smaller hold spacing will still work well I think.

I have not done experiments with hole size and acoustic resistance. The stators in my Martin-Logan ESLs have large holes and small spacing with no damping or other acoustic treatment.

Do you have another ESL project underway?
...j
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Old 26th December 2008, 06:30 PM   #15
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Shock. Ha! Let me tell you about risky business: direct drive amps.

Sad to say, despite the risk, that is by a wide margin the best way to drive ESLs, in my experience.

I ran a Sanders-like amp with 2400 VDC B+ on the tubes (and hence the peak on the stators) for 20 years or so, and with three kids arriving in the house. And using 6 Dayton-Wright elements in two housings looking like a kind of open window frame.

This is very lethal business in a bunch of ways: big voltage, no series resistors, big capacitors holding the B+, big power transformer.... risky.

Mike Wright had all kinds of grief getting the old biddies at the Canadian Standards Assn (like UL) to approve his equipment and the triple-protections shows it. BTW, I think his power supply peak is like 14,000 VDC but adjustable according the humidity and even in the bags, they can be set high enough to crackle when humidity is high.

Except for direct drive amps, I don't think floor-standing speakers are too risky if you use reasonable care.

Question for this thread: Dayton-Wrights need an hour to charge up and play at near regular sensitivity (kind of a rough estimate) and so are left on all the time. Do you folks leave your HV power on all the time?
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Old 27th December 2008, 04:39 AM   #16
j beede is offline j beede  United States
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My Martin-Logans have a circuit that shuts down the dc bias during periods of inactivity. I have had Quads and Acoustats in the past and always left the dc supplies on. Low leakage equals low current flow-no worries. As I recall XG8 and XG10 did not use high resitivity diaphragm coatings so the leakage was not insignificant.
...j
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Old 1st January 2009, 04:19 PM   #17
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I've owned and worked on almost all of the electrostatic headphones ever made (including the HE90 "Orpheus", all Stax models etc.) and none of them have ground present in the headphones. The only exception are the Koss ESP6, 7 and 9 but they very different to say the least.

Nearly all of them have membranes on both sides of the drivers to act as dust covers to that they can keep debris out of the drivers. These membranes are either solid (mylar or pvc sheets) woven nylon fabric. Take something like a Stax Lambda which has mesh screen protecting the driver next to the ear (not grounded), then a PVC dustcover next to the stator. On the back there is a woven nylon mesh and the headphone housing forms a protective barrier.

I've been shocked a few times but only when testing the drivers out in the open and never by stock headphone. Due to the low bias and tiny D/S gap in ES headphones the drive voltages are relatively small. Even a monster such as the Blue Hawaii outputs less the 2000v P-P at full swing and you'll be deaf soon at that level.
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Old 23rd January 2009, 03:44 PM   #18
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Quote:
Originally posted by j beede



Hello Wachara C.
That means that from center-to-center your holes measure 4mm? I am using 1.6mm holes that are 3.2mm, center-to-center. That happened to be the type of perforated sheet steel I had available. My next set of stators will use the same size holes, but closer together. My stators are very rigid and thinner material with smaller hold spacing will still work well I think.

I have not done experiments with hole size and acoustic resistance. The stators in my Martin-Logan ESLs have large holes and small spacing with no damping or other acoustic treatment.

Do you have another ESL project underway?
...j
Hi J,

How is your progress on your ES headphone? I changed my diaphragm to use the plastic wrap for microwave oven, and it sounds a lot better than the mylar sheet I used before. I even compare mine with Koss /E.9. I think mine sounds better. If you have not try this material, I strongly recommend it.

Wachara C.
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Old 4th May 2009, 03:55 PM   #19
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Quote:
Originally posted by Calvin
Since You most often have to add some kind of mechanical resistance to control the typical high Q-value of such ´┐Żopen´┐Ż ESL-designs, a thin layer of acoustic foam (be carefull with colour!) will improve safety and should improve sonics too.
Hi

I have Stax lambda pro, the foam had to be replaced, I have done that.

There was a sheet of that yellowish material inside which I believe was too dense. Not possible to blow air through it.

I removed that, the lambda pro sounds too bright and makes me nervous.

Does it need special damping to prevent high Q / bad impulse response ?

I have SR40 and they sound ok on the same srm1/mkII amplifier, much darker but no highs missing, they also have jellowish sheets, but seem to be more transmissive for air flow.

What would be the best damping material on the outer side between the driver and the housing ?
I have loose silk, any good ?


Also the SR40 are electret type and have only a 2 pole wire for each phone.

What if I cut the wire to one of the stators of the lambda ?
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Old 4th May 2009, 07:26 PM   #20
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The stock mineral wool damping material used by Stax is quite good at taming the dreaded midrange "etch" (an upper midrange peak which many electrostatic headphones have) while not giving them too much of a bass boost. It can't fix the fact that the Lambda Pro is one of the worst Lambdas (recessed midrange, peaky highs and very non-linear bass). I recently set to work damping the current SR-404 model (which have a rather nasty midrange peak) and settled on two sheets of fiber paper on the ear side and a sheet of felt on the back of the driver.

There are only two wires in the SR-40 since it is an electret device, i.e. the membrane has a permanent charge and thus does not need a bias supply. They are still push-pull and if you were to cut one of the stator wires then the distortion would increase quite dramatically.
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