Just curious if anybody has noticed there being some sonic benefits to using a positive vs negative HV bias supply for charging the diaphragm of an ESL.
I have tried both and don't measure any change in sensitivity or notice in change in sound quality. But, I own just one set of ears.
I seem to remember reading once that Sound Lab found that a negatively charged diaphragm collected dust less quickly. But, I can't seem to find the quote now. My own 2 week test did not seem to show any appreciable difference in dust collecting abilities.
Perhaps there are other technical or practical reasons to choose one over the other...
Any comments or thoughts are welcome.
Steve
I have tried both and don't measure any change in sensitivity or notice in change in sound quality. But, I own just one set of ears.
I seem to remember reading once that Sound Lab found that a negatively charged diaphragm collected dust less quickly. But, I can't seem to find the quote now. My own 2 week test did not seem to show any appreciable difference in dust collecting abilities.
Perhaps there are other technical or practical reasons to choose one over the other...
Any comments or thoughts are welcome.
Steve
Charged dust particles are floating around in the air. I remember once so-called air ionizators were common, they allegedly are good for the health, keep you awake while driving etc. I can't remember whether they produced positive or negative ions. Anyway, if the dust particles are charged let's say mostly positive, then a positive polarized diphragm would distract them (at least in theory).
I built a similar ionizer (voltage multiplier, several kilovolts) a while ago, and after a few days of operation I noticed that dust was collected on the wall, so I stopped using it.
I built a similar ionizer (voltage multiplier, several kilovolts) a while ago, and after a few days of operation I noticed that dust was collected on the wall, so I stopped using it.
oshifis said:
Your mentioning of charged dust collecting on walls triggered my memory and I finally recalled where I read the quote from Roger West of Sound Lab concerning using negative bias to reduce dust collection…
It was from his patent 3,935,397…on the last page. Here is an excerpt:
“…The electrostatic dust shield effect assumes that the dust in the air is negatively ionized, which is usually the case. Most actual dust accumulation occurs when the speaker is not reproducing sound --- that is when the DC supply is on but no AC signal is applied. Therefore the DC bias supply is preferably made negative so that dust will be repelled…”
Hi,
It is true that a negative voltage will protect metals (anodic protection) as it prevents the reaction M -> M+ + electron.
The opposite is true for the positive side.
Whether this is a significant factor I don't know. But as replacing HV connections can be pretty clumsy or impossible without tearing apart the whole ESL I used a negative voltage.
Cigarette smoke is supposed to have a positive charge so a positive voltage may be good for repelling this particles. Do not know if this is significant as well.
I have not noticed any change in sound while using + or - voltage.
It is true that a negative voltage will protect metals (anodic protection) as it prevents the reaction M -> M+ + electron.
The opposite is true for the positive side.
Whether this is a significant factor I don't know. But as replacing HV connections can be pretty clumsy or impossible without tearing apart the whole ESL I used a negative voltage.
Cigarette smoke is supposed to have a positive charge so a positive voltage may be good for repelling this particles. Do not know if this is significant as well.
I have not noticed any change in sound while using + or - voltage.
I found this on the web (Google for ionizer + health, 3rd hit):
"Negative ions are found after a rainstorm (falling water creates negative ions) or after a lightning strike. Every home has its own built in negative ionizer- your shower. The smell in the air generated after a rainfall is actually the odor of negatively charged ions in the air."
"Positive ions are found in high concentrations before a storm when it is windy and in areas that have high outdoor air pollution. Sitting in traffic on a busy highway or freeway is a great place to get a dose of positive ions."
"Negative ions are found after a rainstorm (falling water creates negative ions) or after a lightning strike. Every home has its own built in negative ionizer- your shower. The smell in the air generated after a rainfall is actually the odor of negatively charged ions in the air."
"Positive ions are found in high concentrations before a storm when it is windy and in areas that have high outdoor air pollution. Sitting in traffic on a busy highway or freeway is a great place to get a dose of positive ions."
Ozone is always positive, and always bad to breathe
A coronal discharge of either polarity turns O2 into O3+, known as ozone. O- ions can be created by a corona, but these quickly react with O2 to form O3+. So, there is only positive ozone.
Ozone is very reactive and bad for the health. Best not to create it in the first place, but if is is created, best for health reasons to capture and neutralize it on a negatively charged membrane.
Dr. West's assertion that dust tends to be negatively charged and is thus repelled by a negatively charged membrane is another good reason, and I believe he can probably be trusted on this.
A coronal discharge of either polarity turns O2 into O3+, known as ozone. O- ions can be created by a corona, but these quickly react with O2 to form O3+. So, there is only positive ozone.
Ozone is very reactive and bad for the health. Best not to create it in the first place, but if is is created, best for health reasons to capture and neutralize it on a negatively charged membrane.
Dr. West's assertion that dust tends to be negatively charged and is thus repelled by a negatively charged membrane is another good reason, and I believe he can probably be trusted on this.
Actually, if it's neutral, it's not ozone.
If you're not kidding, then you must have ozone mixed up with some other common, bent, triatomic gaseous molecule. Water vapor, maybe? That fits the description, and unless you're a tropical plant or a steam engine, it's not good to have around in significant concentrations.
I wonder how many atoms in a fart molecule? There's a common gas you don't want around in significant concentrations.
Anyway, there is no such thing as "neutral" O3, i.e., with no charge. Ozone is by definition O3+, an ion that has a net charge of +1. Have a look at Ozone - Wikipedia, the free encyclopedia Heck, the whole article is pretty interesting. In case you think Wikipedia is unreliable, I can tell you that this particular article at least is a good one.
If you're not kidding, then you must have ozone mixed up with some other common, bent, triatomic gaseous molecule. Water vapor, maybe? That fits the description, and unless you're a tropical plant or a steam engine, it's not good to have around in significant concentrations.
I wonder how many atoms in a fart molecule? There's a common gas you don't want around in significant concentrations.
Anyway, there is no such thing as "neutral" O3, i.e., with no charge. Ozone is by definition O3+, an ion that has a net charge of +1. Have a look at Ozone - Wikipedia, the free encyclopedia Heck, the whole article is pretty interesting. In case you think Wikipedia is unreliable, I can tell you that this particular article at least is a good one.
Article seems okay, if superficial and abbreviated, and as it says, a corona can produce ions of either polarity, but it skips mentioning the chemistry of O- reacting quickly with O2 to produce O3+. Negative oxygen ions do exist, but don't last long enough to contaminate the air. That is not very interesting in and of itself, but does make the use of negative membrane polarity seem relatively advantageous.
No joke intended. The Wikipedia article seems to have most things correct, and it doesn't say ozone has a charge unless I'm missing a crucial sentence.
If you're looking at the graphics on that website the pluses and minuses in one image:
show the dipole moments associated with the resonance structures. In another (graphic in the upper right corner of the page) they show the average dipole moment--the minuses in parentheses imply partial negative charges. Those symbols just indicate the direction of the shift of electron density within the molecule, though. They don't imply the molecule as a whole has a charge.
Also note that when O3 appears in the many chemical equations on the Wikipedia site it is written as O3 (the neutral molecule) not O3- (the anion called ozonide).
When people talk about ozone, they mean the neutral molecule, O3.
Few
If you're looking at the graphics on that website the pluses and minuses in one image:
show the dipole moments associated with the resonance structures. In another (graphic in the upper right corner of the page) they show the average dipole moment--the minuses in parentheses imply partial negative charges. Those symbols just indicate the direction of the shift of electron density within the molecule, though. They don't imply the molecule as a whole has a charge.
Also note that when O3 appears in the many chemical equations on the Wikipedia site it is written as O3 (the neutral molecule) not O3- (the anion called ozonide).
When people talk about ozone, they mean the neutral molecule, O3.
Few
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At the time the book of Fikier just was published, metalized Mylar was the only available ready to buy conductive material. After some time, the persons selling this film put a note together with the film which mentioned the evaporation of the metal. Their advice was to use a high voltage supply generating a positive instead of a negative voltage in order to prevent this kind of deterioation. The theory behind this and its effectiveness is unknown to me. But this might explain the thing you have read.
There are other reasons for evaporation, but they are independent from polarity.
b.t.w., ozone is uncharged indeed, but ofcourse very reactive
Nooooooooo!!!!!!!
(look up "electronegativity" and try understanding what it is and how that relates to oxygen)
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