Hi this isnmy first post and it is regarding safety with the diy esl. A local audio guru(ahem!) has informed my friends of my almost certain death if I continue the construction of my speakers. Because he knows a bloke that ionised the room and lost half of his face etc. I have seen no such worries on the internet. Does anybpody know of any such stories or is a matter of hot air a I suspect it to be. Is there any experimenter out there alive enough to give the low down on this?
Thanks in advance
Thanks in advance
For most ESL designs, hot air. The most spectacular failure I've seen was from a Beveridge wannabe with a metallized diaphragm. One loud passage and... POOF! Flames.
Adding to Bill's comment there's the ever present danger of opening a interdimensional portal due to a high-voltage discharge and resulting em-field that rips a hole in the fabric of time-space, imagine that!
But seriously the high-voltage cascades used to charge the foil carry a dangerously high voltage. If you use the tried-and-tested dual transformer design and a bunch of caps and diodes you'll feel a sharp pain when you touch the foil when powered up.
If you go with the 'minimalist' approach of a cascade running straight off the mains you could end up in the ER, as then there's no real current limiting other than the diodes that usually push about 1A, either way high-voltage demands respect.
I'd suggest you Google for ESL Cook Book by R Sanders and read through that to get an impression of the do's and don't's.
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
But seriously the high-voltage cascades used to charge the foil carry a dangerously high voltage. If you use the tried-and-tested dual transformer design and a bunch of caps and diodes you'll feel a sharp pain when you touch the foil when powered up.
If you go with the 'minimalist' approach of a cascade running straight off the mains you could end up in the ER, as then there's no real current limiting other than the diodes that usually push about 1A, either way high-voltage demands respect.
I'd suggest you Google for ESL Cook Book by R Sanders and read through that to get an impression of the do's and don't's.
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
There is no chance that you will ionize yourself to death and have half your face fall off with your DIY esl speakers. What RUBISH! The only real danger is of getting zapped by high voltage if you are not carefull. You will only do that once.
The only speaker that can ionize air is a plasma speaker that is not enclosed. There was a story going around many years ago about Nelson Pass and a plasma speaker he built. But I doubt if that was true.
Sander makes a very good point about getting the ESL Cookbook. There is a quite a bit of good info on ESL.
Do not pay any attention to your local audio guru. As with most of these audio guru types there mouths are one thousand bigger than their knowledge.
Andy Bartha
The only speaker that can ionize air is a plasma speaker that is not enclosed. There was a story going around many years ago about Nelson Pass and a plasma speaker he built. But I doubt if that was true.
Sander makes a very good point about getting the ESL Cookbook. There is a quite a bit of good info on ESL.
Do not pay any attention to your local audio guru. As with most of these audio guru types there mouths are one thousand bigger than their knowledge.
Andy Bartha
Many thanks for your excellent and informed answers to my post. you have put my mind at rest.I have seen the the results of people just playing around with electricity. One fly in the room and blam ..... no more dinner party invites.
Seriously though it is very difficult to stand up in front of people with little or no interest in the subject, ones family generally, and claim that twenty years of reading and fiddling around with components has given you some residual familiarity with the the subject if there is the barfly expert standing next to you telling tales to chill the blood.
What an excellent community.
and many thanks, I was so miserable at the thought of having to stop creating my masterpiece.
Seriously though it is very difficult to stand up in front of people with little or no interest in the subject, ones family generally, and claim that twenty years of reading and fiddling around with components has given you some residual familiarity with the the subject if there is the barfly expert standing next to you telling tales to chill the blood.
What an excellent community.
and many thanks, I was so miserable at the thought of having to stop creating my masterpiece.
The danger is not in the HV bias supply, unless it is not built properly.
By built properly, I mean there should be no high energy parts in it- i.e. don't use a big transformer for voltage step-up, don't use any large capacitances, and put a very large resistance (>10 Megohms) between the supply and the ESL diaphragm. You should be able to touch the ESL bias output with your bare finger and get nothing more than the shock you get when you walk across a carpeted floor and touch a grounded lamp/doorknob/etc.
The real danger in ESLs is the possibility of coming into contact with the stators while the speaker is operating. The audio transformers that step the amplifier output voltage up to a few thousand volts can deliver a very bad shock. I know this from experience. I was left with a very sore arm and an interesting perforation pattern from the stators burned into my thumb and index finger.
ESLs should always be built with some form of mechanical barrier that prevents anyone from accidently coming into contact with the stators or the wiring around the audio transformers. Don't skip this part of your design, and be very careful when testing.
I_F
By built properly, I mean there should be no high energy parts in it- i.e. don't use a big transformer for voltage step-up, don't use any large capacitances, and put a very large resistance (>10 Megohms) between the supply and the ESL diaphragm. You should be able to touch the ESL bias output with your bare finger and get nothing more than the shock you get when you walk across a carpeted floor and touch a grounded lamp/doorknob/etc.
The real danger in ESLs is the possibility of coming into contact with the stators while the speaker is operating. The audio transformers that step the amplifier output voltage up to a few thousand volts can deliver a very bad shock. I know this from experience. I was left with a very sore arm and an interesting perforation pattern from the stators burned into my thumb and index finger.
ESLs should always be built with some form of mechanical barrier that prevents anyone from accidently coming into contact with the stators or the wiring around the audio transformers. Don't skip this part of your design, and be very careful when testing.
I_F
I_Forgot is right. Stators are the problem.
This is such an important question that I_Forgot’s excellent response deserves to be “seconded”. Fortunately the diaphragm’s HV bias supply already needs a high resistance to ensure constant charge for low distortion. This resistance also is protective for humans. The typically >10MEG resistor should be an integral part of the HV supply (close as possible to the diodes and caps) so that any wiring used to distribute the HV to the diaphragm(s) will be after this resistor and will be current limited against accidental contact.
But the stators can be deadly when music or test signals are playing. Using a HV probe, I have watched on a scope thousands of volts of music playing on my Quad ESL-63 after the step-up transformer (or, in my case, coming from my direct-drive 833 amps). Whether a transformer step-up or direct-drive is used, both sources have the relatively low driving impedance necessary to drive the capacitance of the ESL elements at higher frequencies. This means that not only are high voltages present, but also deadly high currents (relatively). As a side note, I always wondered how Martin Logan, InnerSound or any other ESL manufacturer can get away with exposed stators. The MLs are coated with some kind of epoxy, but still, a scratch or a wet finger finding a tiny hole in the coating could be dangerous. I suppose you’d have to figure out how to touch both stators simultaneously, and maybe that has saved the day. I’ve never heard of anyone getting fried with a commercial speaker, but still I wonder.
This is such an important question that I_Forgot’s excellent response deserves to be “seconded”. Fortunately the diaphragm’s HV bias supply already needs a high resistance to ensure constant charge for low distortion. This resistance also is protective for humans. The typically >10MEG resistor should be an integral part of the HV supply (close as possible to the diodes and caps) so that any wiring used to distribute the HV to the diaphragm(s) will be after this resistor and will be current limited against accidental contact.
But the stators can be deadly when music or test signals are playing. Using a HV probe, I have watched on a scope thousands of volts of music playing on my Quad ESL-63 after the step-up transformer (or, in my case, coming from my direct-drive 833 amps). Whether a transformer step-up or direct-drive is used, both sources have the relatively low driving impedance necessary to drive the capacitance of the ESL elements at higher frequencies. This means that not only are high voltages present, but also deadly high currents (relatively). As a side note, I always wondered how Martin Logan, InnerSound or any other ESL manufacturer can get away with exposed stators. The MLs are coated with some kind of epoxy, but still, a scratch or a wet finger finding a tiny hole in the coating could be dangerous. I suppose you’d have to figure out how to touch both stators simultaneously, and maybe that has saved the day. I’ve never heard of anyone getting fried with a commercial speaker, but still I wonder.
Re: I_Forgot is right. Stators are the problem.
Maybe no one has ever lived to tell the tale!
I have always wondered the same thing about MLs. Maybe they put resistors in series to limit current, but not so large as to reduce the speaker output in the audible range (or maybe they do that to act as a LPF to roll off the HF response of the speaker)...
I_F
Brian Beck said:
Maybe no one has ever lived to tell the tale!
I have always wondered the same thing about MLs. Maybe they put resistors in series to limit current, but not so large as to reduce the speaker output in the audible range (or maybe they do that to act as a LPF to roll off the HF response of the speaker)...
I_F
Ummm... contact with the stators should not be dangerous. They are at ground when the unit is NOT playing.
When playing they are at some rather variable AC voltage which depending upon the speaker and how loud it is playing may or may not be high enough current or voltage to bother you under normal home circumstances...
But, I'd rather not be holding the secondary of a step up transformer that is running the stators, or the uninsulated stator AND holding a nice solid ground...
So for merely ordinary people, some touchy/kids/fool protection of the stators is probably essential... grille cloth at a suitable distance from the stators may suffice?
The high voltage supply should NOT be a high current supply. It should be a low current high voltage type - typically either a regulated switcher or more commonly a multi-stage diode "quintupler" or such (like a voltage doubler, but stacked up to produce some HV from something like a wall wart or a small iso tranny). The latter, the wall wart/12vac small transformer virtually eliminates any possibility of injury from high voltage.
Although you can take a nice jump if *you* serve as the discharge path for the ESL panel itself... 😀
As far as ionizing the air in the room, not!
The two speakers that MIGHT ionize the air are a pure plasma speaker - there was one made commercially back in the early 80s and advertised for a short time... spectacularly low output, btw... and/or a plasma tweeter of the ionovac/ionofane ilk will produce some ozone.
Oddly, I kinda like some ozone in a room... via electrostatic air cleaners - a nice clean smell... your preferences may vary on that.
The one that your fiend, I mean friend my have been thinking of is/was the Hill Plasmatronic, which used a HeNeAr or similar gas, (the patent didn't call for the the HeNeAr, but just He, but I thought the purple glow was due to the Ar, but apparently not - but i diverge) which did tend to fill the room with nicely ionized air and inert gas... so a positive ventalation system was a good thing to have with that extraordinary speaker.
_-_-bear
When playing they are at some rather variable AC voltage which depending upon the speaker and how loud it is playing may or may not be high enough current or voltage to bother you under normal home circumstances...
But, I'd rather not be holding the secondary of a step up transformer that is running the stators, or the uninsulated stator AND holding a nice solid ground...
So for merely ordinary people, some touchy/kids/fool protection of the stators is probably essential... grille cloth at a suitable distance from the stators may suffice?
The high voltage supply should NOT be a high current supply. It should be a low current high voltage type - typically either a regulated switcher or more commonly a multi-stage diode "quintupler" or such (like a voltage doubler, but stacked up to produce some HV from something like a wall wart or a small iso tranny). The latter, the wall wart/12vac small transformer virtually eliminates any possibility of injury from high voltage.
Although you can take a nice jump if *you* serve as the discharge path for the ESL panel itself... 😀
As far as ionizing the air in the room, not!
The two speakers that MIGHT ionize the air are a pure plasma speaker - there was one made commercially back in the early 80s and advertised for a short time... spectacularly low output, btw... and/or a plasma tweeter of the ionovac/ionofane ilk will produce some ozone.
Oddly, I kinda like some ozone in a room... via electrostatic air cleaners - a nice clean smell... your preferences may vary on that.
The one that your fiend, I mean friend my have been thinking of is/was the Hill Plasmatronic, which used a HeNeAr or similar gas, (the patent didn't call for the the HeNeAr, but just He, but I thought the purple glow was due to the Ar, but apparently not - but i diverge) which did tend to fill the room with nicely ionized air and inert gas... so a positive ventalation system was a good thing to have with that extraordinary speaker.
_-_-bear
bear said:
I can assure you that under "normal home circumstances" the AC voltage on the stators is MORE than enough to hurt you. No, it may not electrocute you, but it will certainly cause burns, pain, and possibly flailing about that might lead to injuries due to falls, knocking down furniture, bumping one's head, etc.
The potential danger should not be dismissed. It must be recognized and minimized by the design of the speaker.
I_F
Again, LISTEN to what I_Forgot is saying!
I feel it necessary to really "slam dunk" this point, because we don't want any DIY friends reading this thread to be burned or to die! I think Bear’s comments might give false comfort to a DIYer.
Let's look at an example using a commercial speaker: Let’s drive a Quad ESL-63 with 2.83 Vrms, the voltage equivalent to only 1 watt into 8 ohms (that’s about 86 dB SPL - not very loud). I’ve measured the Quad’s tandem pair of transformers’ step-up ratio at around 1:170. The stators will then see 481 Vrms of push-pull voltage across them. Assuming a sine-wave, that means peaks of 680 V. The driving impedance from the transformers’ secondaries is in the order of a few tens of Kohms because of transformed resistances from the primary circuit, so there is little current limiting compared to skin resistance. Folks, 680 V from a one-watt input is plenty enough to kill!
Now drive the Quad to 95 dB or louder, and, well, you do the math!
I feel it necessary to really "slam dunk" this point, because we don't want any DIY friends reading this thread to be burned or to die! I think Bear’s comments might give false comfort to a DIYer.
Let's look at an example using a commercial speaker: Let’s drive a Quad ESL-63 with 2.83 Vrms, the voltage equivalent to only 1 watt into 8 ohms (that’s about 86 dB SPL - not very loud). I’ve measured the Quad’s tandem pair of transformers’ step-up ratio at around 1:170. The stators will then see 481 Vrms of push-pull voltage across them. Assuming a sine-wave, that means peaks of 680 V. The driving impedance from the transformers’ secondaries is in the order of a few tens of Kohms because of transformed resistances from the primary circuit, so there is little current limiting compared to skin resistance. Folks, 680 V from a one-watt input is plenty enough to kill!
Now drive the Quad to 95 dB or louder, and, well, you do the math!
680volts AC will give you a nasty jolt for sure...
and I don't want to give anyone a false sense of security.
But, there is only voltage present when playing, an important
point.
And, nothing at all will happen unless you provide a path to ground or to the other stator if and when you touch that stator while music is playing.
P = I * E
1 = I * 680
1/680 = I or ~ .00147 amperes
Using the example given. Not a very dangerous current.
STILL: KEEP UR PAWS AWAY FROM HIGH VOLTAGES!!
_-_-bear
and I don't want to give anyone a false sense of security.
But, there is only voltage present when playing, an important
point.
And, nothing at all will happen unless you provide a path to ground or to the other stator if and when you touch that stator while music is playing.
P = I * E
1 = I * 680
1/680 = I or ~ .00147 amperes
Using the example given. Not a very dangerous current.
STILL: KEEP UR PAWS AWAY FROM HIGH VOLTAGES!!
_-_-bear
One more time...
I'm weary of this point, but I'll have another go at it due to its importance it life and limb.
While your arithmetic is correct regarding the current driven by 680 V at 1 watt, it is irrelevant to the risk of shock. I used 1 watt to establish a low-power reference point in response to Bears’ point about “may or may not be high enough current or voltage to bother you under normal home circumstances. “ Once 680 V has been applied, the current is a function of the load resistance. If sweaty skin were to contact the 680V, more current will flow than that calculated for the speaker alone. It all depends on lots of factors, such as the other circuit resistances, one’s skin resistance, how sweaty, how wet, pressure of contact and duration of contact, etc. I’m not guaranteeing death at these levels, but I wouldn’t be surprised to hear of it either.
The Merck medical manual says: "At currents as low as 60 to 100 milliamperes, low-voltage (110-220 volts), 60-hertz alternating current traveling through the chest for a split second can cause life-threatening irregular heart rhythms. About 300-500 milliamperes of direct current is needed to have the same effect."
I suspect there are amplifier/step-up transformer combinations that can easily deliver 60 mA at the secondary long enough to kill, even at “normal” listening levels.
Bear’s point about needing contact with both stators and/or ground is correct of course (it was already stated earlier). As is his point about needing a signal present to create this risk, obviously.
But this is the DiyAudio forum, isn’t it? Is it so hard to imagine a DIYer building an ESL with bare panels on the test bench, wires strewn every where and a signal generator cranking out steady sine waves at levels exceeding 1 watt through a step-up?
Perhaps we do all agree: BE CAREFUL OF THE SECONDARY CIRCUIT AND STATORS WITH MUSIC OR TEST SIGNALS! Enough said, I hope.
I'm weary of this point, but I'll have another go at it due to its importance it life and limb.
While your arithmetic is correct regarding the current driven by 680 V at 1 watt, it is irrelevant to the risk of shock. I used 1 watt to establish a low-power reference point in response to Bears’ point about “may or may not be high enough current or voltage to bother you under normal home circumstances. “ Once 680 V has been applied, the current is a function of the load resistance. If sweaty skin were to contact the 680V, more current will flow than that calculated for the speaker alone. It all depends on lots of factors, such as the other circuit resistances, one’s skin resistance, how sweaty, how wet, pressure of contact and duration of contact, etc. I’m not guaranteeing death at these levels, but I wouldn’t be surprised to hear of it either.
The Merck medical manual says: "At currents as low as 60 to 100 milliamperes, low-voltage (110-220 volts), 60-hertz alternating current traveling through the chest for a split second can cause life-threatening irregular heart rhythms. About 300-500 milliamperes of direct current is needed to have the same effect."
I suspect there are amplifier/step-up transformer combinations that can easily deliver 60 mA at the secondary long enough to kill, even at “normal” listening levels.
Bear’s point about needing contact with both stators and/or ground is correct of course (it was already stated earlier). As is his point about needing a signal present to create this risk, obviously.
But this is the DiyAudio forum, isn’t it? Is it so hard to imagine a DIYer building an ESL with bare panels on the test bench, wires strewn every where and a signal generator cranking out steady sine waves at levels exceeding 1 watt through a step-up?
Perhaps we do all agree: BE CAREFUL OF THE SECONDARY CIRCUIT AND STATORS WITH MUSIC OR TEST SIGNALS! Enough said, I hope.
I think it is important to keep this in persepective.
Anyone who is a DIYer and does anything with tube gear at all is
exposed to a much greater risk of electric shock than with the typical ESL...
Having grabbed both, I'll tell you that I'll take the ESL over any tube gear's B+ or PS cap, if I had to chose.
And again, you can touch any high voltage, if there is no path to ground, there is no danger.
The Merck manual's warnings are real, but the path for the electricity must be through the heart to have the effect that it refers to. I'm not suggesting that anyone should try it, or disregard any SAFETY precautions! ALWAYS TAKE SAFETY PRECAUTIONS AROUND ELECTRICAL CIRCUITS!!
_-_-bear
Anyone who is a DIYer and does anything with tube gear at all is
exposed to a much greater risk of electric shock than with the typical ESL...
Having grabbed both, I'll tell you that I'll take the ESL over any tube gear's B+ or PS cap, if I had to chose.
And again, you can touch any high voltage, if there is no path to ground, there is no danger.
The Merck manual's warnings are real, but the path for the electricity must be through the heart to have the effect that it refers to. I'm not suggesting that anyone should try it, or disregard any SAFETY precautions! ALWAYS TAKE SAFETY PRECAUTIONS AROUND ELECTRICAL CIRCUITS!!
_-_-bear
There doesn't have to be a path through your heart to hurt you.
I burned my hand badly, and fortunately there wasn't anything in the space where I flailed my arm so I didn't add additional pain to the injury by hitting a wall, or door, or knocking down an expensive antique vase, or etc.
You can't think to yourself before you get zapped, "now if I get zapped, I will swing my arm this way to avoid that plate glass window" and then expect to be able to act on it when the time comes. When you are getting zapped there is no predicting what will happen no matter what is around you or whatever plans you make. If you don't get some sort of secondary injury, you are lucky, and that is all.
All this should not scare anyone away from building ESLs. It should simply raise your awareness of potential danger so that you can prevent injury to yourself and others by taking adequate precautions. Working on ESLs is no more dangerous than working on anything else that has high voltage present. You shouldn't build an amplifier and leave all the wiring exposed where people can touch it. Just treat ESL construction with the same respect and you'll be OK.
I_F
I burned my hand badly, and fortunately there wasn't anything in the space where I flailed my arm so I didn't add additional pain to the injury by hitting a wall, or door, or knocking down an expensive antique vase, or etc.
You can't think to yourself before you get zapped, "now if I get zapped, I will swing my arm this way to avoid that plate glass window" and then expect to be able to act on it when the time comes. When you are getting zapped there is no predicting what will happen no matter what is around you or whatever plans you make. If you don't get some sort of secondary injury, you are lucky, and that is all.
All this should not scare anyone away from building ESLs. It should simply raise your awareness of potential danger so that you can prevent injury to yourself and others by taking adequate precautions. Working on ESLs is no more dangerous than working on anything else that has high voltage present. You shouldn't build an amplifier and leave all the wiring exposed where people can touch it. Just treat ESL construction with the same respect and you'll be OK.
I_F
I_Forgot said:
Following the thread - my post regarding path through the heart was in response to the post re "the Merck Manual" which made a reference to damage to the heart.
Clearly, any electric shock can hurt you.
BUT, there MUST be a path to GROUND from the HV source for you to become hurt.
_-_-bear
From what I was taught, worst case is a shock path that travels through both your heart annd brain. i.e. From left ear to right hand or leg, or right ear to left hand or leg. (I worked on power systems for the phone company and received regular safety training)
Of course, from left hand to right hand will provide a decent path through the heart as well. (it is why we are told to keep one hand in our pockets when working on live circuits)
I don't thinnk you need a path to ground to get a shock that will kill you, just a path that delivers enough current through either your heart or brain. If your skin is wet, or the voltage high enough, it does not take much current.
My advice, be careful... you do want to enjoy your hobby.
Joe L.
Of course, from left hand to right hand will provide a decent path through the heart as well. (it is why we are told to keep one hand in our pockets when working on live circuits)
I don't thinnk you need a path to ground to get a shock that will kill you, just a path that delivers enough current through either your heart or brain. If your skin is wet, or the voltage high enough, it does not take much current.
My advice, be careful... you do want to enjoy your hobby.
Joe L.
bear said:
No, in this case, there does not have to be a path to ground. There only has to be a path from the front side stator to the back side stator, which due to the thinness of ESL drivers, is most frequently and conviently provided by one hand, specifically the thumb and one or more fingers.
For the sake of everyone's safety, please give up your insistence about grounding. You're going to make people think that if they don't grab a cold water pipe AND an HV wire they can't get hurt. This is dangerous misinformation.
I_F
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