I'll admit to being knocked cold when I accidently discharged the bank of Rubycon photoflash filter caps in the power supply of a tube phono stage I built back in 1982. I was working alone and late at night, the supply had been shut off for a while. I woke up "later"under the workbench across the aisle. No lasting harm once my vision turned back after a few minutes. Two words--bleeder resistors. Lesson learned.
Have you ever discharged a diaphram in your ESL to youself? Ever provided a human conduction path between your stators? I am building ES headphones and am considering dropping the effort since it may be "stupidly" dangerous. I have 20 MOhms in series with the bias supply, but I am more worried about the HVAC on the stators. What has your experience been?
...j
Have you ever discharged a diaphram in your ESL to youself? Ever provided a human conduction path between your stators? I am building ES headphones and am considering dropping the effort since it may be "stupidly" dangerous. I have 20 MOhms in series with the bias supply, but I am more worried about the HVAC on the stators. What has your experience been?
...j
Hi,
when working with a very high resistance coating discharging even large membranes won´t knock You down. Besides others this is a major advantage of high resistance coatings. Since the membrane is encapsulated betwen the stators this helps in getting in touch with it.
But it was kind of a rebirthing experience when I accidently touched one pole of the audio trannies while playing music.....what a beat
So its the stators where You have to put Your eyes on.
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. Attached is a exploded view of the Sennheiser Orpheus capsules. In the middle there are the two spacer rings of which one holds the diaphragm. Then follow the two stators which were made from special hard glass with etched holes to get the right degree of transmittance. The glass was gold sputtered (I was told (rumoured) that the gold plating didn´t proof to be longtime stable.
It appears as if the gold plating is insulated with a laquer towards the membrane-side, but not towards the outer side.
A pair of rings holding kind of a membrane or extreme fine mesh seems to function as a isolation barrier to the outside.
Quad uses the trick of encapsulating the panel with a very thin film. The film would feature the best insulation values, complete encapsulation of potentially dangerous parts, easy mounting, total acoustic transparency and low cost.
Since You most often have to add some kind of mechanical resistance to control the typical high Q-value of such ´open´ ESL-designs, a thin layer of acoustic foam (be carefull with colour!) will improve safety and should improve sonics too.
jauu
Calvin
when working with a very high resistance coating discharging even large membranes won´t knock You down. Besides others this is a major advantage of high resistance coatings. Since the membrane is encapsulated betwen the stators this helps in getting in touch with it.
But it was kind of a rebirthing experience when I accidently touched one pole of the audio trannies while playing music.....what a beat
So its the stators where You have to put Your eyes on.
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. Attached is a exploded view of the Sennheiser Orpheus capsules. In the middle there are the two spacer rings of which one holds the diaphragm. Then follow the two stators which were made from special hard glass with etched holes to get the right degree of transmittance. The glass was gold sputtered (I was told (rumoured) that the gold plating didn´t proof to be longtime stable.
It appears as if the gold plating is insulated with a laquer towards the membrane-side, but not towards the outer side.
A pair of rings holding kind of a membrane or extreme fine mesh seems to function as a isolation barrier to the outside.
Quad uses the trick of encapsulating the panel with a very thin film. The film would feature the best insulation values, complete encapsulation of potentially dangerous parts, easy mounting, total acoustic transparency and low cost.
Since You most often have to add some kind of mechanical resistance to control the typical high Q-value of such ´open´ ESL-designs, a thin layer of acoustic foam (be carefull with colour!) will improve safety and should improve sonics too.
jauu
Calvin
Attachments
Hi,
part II:
Within the wooden frame that houses the ESL-capsule two sheets of finely stamped steel protect the capsule from anything touching it.
Each capsule is wired by a three-wire-cord to the supply, hence, there is no PE-wire leading to the HP.
The bias voltage is 500Vdc and the associated amp could put out ~400Veff (1130Vpp).
jauu
Calvin
part II:
Within the wooden frame that houses the ESL-capsule two sheets of finely stamped steel protect the capsule from anything touching it.
Each capsule is wired by a three-wire-cord to the supply, hence, there is no PE-wire leading to the HP.
The bias voltage is 500Vdc and the associated amp could put out ~400Veff (1130Vpp).
jauu
Calvin
Attachments
Dear J,
Don't stop! Once you have finished building it, you won't regret. If you are really worried, I have another full set of stator and spacer for you. They are made of one sided PCB just like mine. The side that will be touching your ear is fiberglass and it should be very safe. I bias mine up to 1200V and I dare to put them against my ears. If you are interested, let me know.
By the way, I got an electrical shock when I was building my ES headphone. It didn't hurt as much as the shock from the capacitor of a tube amp.
Wachara C.
Don't stop! Once you have finished building it, you won't regret. If you are really worried, I have another full set of stator and spacer for you. They are made of one sided PCB just like mine. The side that will be touching your ear is fiberglass and it should be very safe. I bias mine up to 1200V and I dare to put them against my ears.
If you are interested, let me know.By the way, I got an electrical shock when I was building my ES headphone. It didn't hurt as much as the shock from the capacitor of a tube amp.
Wachara C.
Actually the charge stored on the diaphram can do some harm... Years ago I was following the instructions from Acoustat regarding the discharging of a panel while detaching the interface box. The gunshot-like sound and bright spark casued me to flinch and I smashed my elbow into the equipment stand behind me as I relexively pulled back!
The Orpheus solution is a good one--grounded screen to shield fingers and outer ears from HVAC. Of course, from an electrical point of view, the stators are what I worry about. Quad used front (extruded) and rear (expanded) metal grilles on the ESL. Acoustat used way thick plastic stators (fluorescent light diffusers?) and cloth. Dayton Wright used plastic bags and grille cloth. Infinity used cloth grilles, same for Sound Labs, Koss and KLH. Other than Martin Logan (and DIY ESLs) what other ESL allows the stators to be touched directly? There are some small ESLs from Holland or Denmark that look like Martin Logans, they too may permit touchingthe stator.
How are you guys protecting yourselves and others from feeling the stator "pain"? Is there a coating I can apply in my basement workshop?
...j
The Orpheus solution is a good one--grounded screen to shield fingers and outer ears from HVAC. Of course, from an electrical point of view, the stators are what I worry about. Quad used front (extruded) and rear (expanded) metal grilles on the ESL. Acoustat used way thick plastic stators (fluorescent light diffusers?) and cloth. Dayton Wright used plastic bags and grille cloth. Infinity used cloth grilles, same for Sound Labs, Koss and KLH. Other than Martin Logan (and DIY ESLs) what other ESL allows the stators to be touched directly? There are some small ESLs from Holland or Denmark that look like Martin Logans, they too may permit touchingthe stator.
How are you guys protecting yourselves and others from feeling the stator "pain"? Is there a coating I can apply in my basement workshop?
...j
chinsettawong said:Dear J,
Don't stop! Once you have finished building it, you won't regret. If you are really worried, I have another full set of stator and spacer for you. They are made of one sided PCB just like mine. The side that will be touching your ear is fiberglass and it should be very safe. I bias mine up to 1200V and I dare to put them against my ears.
By the way, I got an electrical shock when I was building my ES headphone. It didn't hurt as much as the shock from the capacitor of a tube amp.
Wachara C.
Okay, okay, I'll keep going
Wachara, what size holes and hole to hole spacing in your perforated PCB material? If I can find some aethetically pleasing, high carbon steel mesh I will probably adapt my design to include inner and outer grounded shields. I hat the idea of having to run ground wires--but I hate being shocked more! As I mentioned earlier, I worry about the reliability of the ground path to the shields--easy to forget about until they fail....j
Hi,
@jbeede: If You want correct information...reading helps!
The Orpheus doesn´t use grounded grids!
The protector film has the advantage that it is a ´passive´ protection, that doesn´t rely on any connection to PE or special circuitry. Too even the smallest things that may protrude through to the stators or even the diaphragm, e.g. hair, is prevented from doing so. Ageing effects should be reduced as well.
A grounded grid probabely won´t prevent hair from getting in contact with the stators.
jauu
Calvin
oh, btw. My stators can be touched without any harm at full play too ;-)
@jbeede: If You want correct information...reading helps!
The Orpheus doesn´t use grounded grids!
The protector film has the advantage that it is a ´passive´ protection, that doesn´t rely on any connection to PE or special circuitry. Too even the smallest things that may protrude through to the stators or even the diaphragm, e.g. hair, is prevented from doing so. Ageing effects should be reduced as well.
A grounded grid probabely won´t prevent hair from getting in contact with the stators.
jauu
Calvin
oh, btw. My stators can be touched without any harm at full play too ;-)
OK, I'll probably become the poster boy here!
Disconnected some Acoustat 2+2's from interface about 10 yrs.
ago to move (8ft ceiling, so had to dissasemble and tilt down
to get them out). It's a nice quick jolt!, but is over in less
then a second. I know the Acoustats use about 5KV. to charge.
Disconnected some Acoustat 2+2's from interface about 10 yrs.
ago to move (8ft ceiling, so had to dissasemble and tilt down
to get them out). It's a nice quick jolt!, but is over in less
then a second. I know the Acoustats use about 5KV. to charge.
j beede said:
Okay, okay, I'll keep going
...j
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.
Calvin said:Hi,
@jbeede: If You want correct information...reading helps!
The Orpheus doesn´t use grounded grids!
The protector film has the advantage that it is a ´passive´ protection, that doesn´t rely on any connection to PE or special circuitry. Too even the smallest things that may protrude through to the stators or even the diaphragm, e.g. hair, is prevented from doing so. Ageing effects should be reduced as well.
A grounded grid probabely won´t prevent hair from getting in contact with the stators.
jauu
Calvin
oh, btw. My stators can be touched without any harm at full play too ;-)
Hello Calvin,
Is it your habit to insult people whom you don't even know? I do read English rather well, your reply I cannot easily decipher.
You have measured the resistance to chassis ground from the formed screens on your Orpheus? Hard to imagine that Sennheiser would allow any metal to float in the presence of an electirc field. Why would I care if my hair touched a stator? I should think that woven hair would make a fine, if impractical stator insulator. You have simultaneously touched your front and rear stators harmlessly? Are they coated like Martin-Logans?
...j
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??
jauu
Calvin
ps: sorry for not answering Your other Qs, but I need to work on my ´hard to decipher´ English.
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??
jauu
Calvin
ps: sorry for not answering Your other Qs, but I need to work on my ´hard to decipher´ English.
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
...j
chinsettawong said:
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
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?
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?
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
...j
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.
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.
j beede said:
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.
Calvin said:
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 ?
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.
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.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.