Hi Guys
I can find no specific information regarding THD vs bias voltage, with all other things being equal.
It seems that the reason higher bias voltages were used in the first place was to attain higher SPLs - something I have no interest in. 100dB will damage your hearing faster than 70dB and I prefer to enjoy a lifetime of music rather than some really loud aurally compressed noise for a little while.
From the equations of force on the diaphragm, force is proportional to both bias voltage and to signal voltage.
From data available, THD rises with signal level.
The above suggests that THD _may_ increase with bias voltage as well, but that seems counter-intuitive considering how THD tends to fall with higher supply voltages in electronic circuits for a given signal size.
Anyway, if someone has some insight I would appreciate it, as I'm sure others might too.
Have fun
Kevin O'Connor
I can find no specific information regarding THD vs bias voltage, with all other things being equal.
It seems that the reason higher bias voltages were used in the first place was to attain higher SPLs - something I have no interest in. 100dB will damage your hearing faster than 70dB and I prefer to enjoy a lifetime of music rather than some really loud aurally compressed noise for a little while.
From the equations of force on the diaphragm, force is proportional to both bias voltage and to signal voltage.
From data available, THD rises with signal level.
The above suggests that THD _may_ increase with bias voltage as well, but that seems counter-intuitive considering how THD tends to fall with higher supply voltages in electronic circuits for a given signal size.
Anyway, if someone has some insight I would appreciate it, as I'm sure others might too.
Have fun
Kevin O'Connor
100 dB max peak SPL isn't really enough - real, live, unamplified music sometimes has dynamic peaks of >+20 dB re the ave SPL - may only be ms peaks of the initial transient of a percussion instrument - not clipping rare peaks is a good goal
you need to read Preventing Hearing Damage When Listening With Headphones | HeadWize twice, both for safe limits and for real SPL ranges
constant charge ES operation normally uses the max V that the diaphram can handle, either from electro-mechanical stability or dielectric breakdown
you need to read Preventing Hearing Damage When Listening With Headphones | HeadWize twice, both for safe limits and for real SPL ranges
constant charge ES operation normally uses the max V that the diaphram can handle, either from electro-mechanical stability or dielectric breakdown
The bias voltage in ESL is directly corelated with the efficiency. When you have high efficiency, you don't have to crank up the volume so much to get a decent listening level. Therefore, you get lower THD.
Hi Guys
The only THD vs level graphs that I've seen for ESL headphones were for Stax. The graph showed higher THD at higher SPL - perfectly expected.
Does anyone have any FACTS about THD vs bias magnitude? Chinsettawong, is your statement fact or opinoin?
I do not wish to discuss off-topic loudness issues, but... Jean, you should read that article and reconsider your statement that "100dB isn't really enough".
Have fun
Kevin O'Connor
The only THD vs level graphs that I've seen for ESL headphones were for Stax. The graph showed higher THD at higher SPL - perfectly expected.
Does anyone have any FACTS about THD vs bias magnitude? Chinsettawong, is your statement fact or opinoin?
I do not wish to discuss off-topic loudness issues, but... Jean, you should read that article and reconsider your statement that "100dB isn't really enough".
Have fun
Kevin O'Connor
don't need much google fu if you really wanted to be educated on the loudness issue - what part of "dynamic", "peak" - not long term, not average is a problem for you to understand?
"forte" SPL:
as for ES distortion - constant charge operation doesn't have any other term involving bias V than the (fixed at audio frequency) charge which gives force/Area/Vdrive so just tun down Vdrive if you don't want it loud
the rest of the ES distortion terms would be related to diaphragm spring constant vs displacement - move the diaphragm the same distance and you get the same nonlinear spring effect
and the name is John - one of many Who are all the Lectroids named John?
"forte" SPL:
as for ES distortion - constant charge operation doesn't have any other term involving bias V than the (fixed at audio frequency) charge which gives force/Area/Vdrive so just tun down Vdrive if you don't want it loud
the rest of the ES distortion terms would be related to diaphragm spring constant vs displacement - move the diaphragm the same distance and you get the same nonlinear spring effect
and the name is John - one of many Who are all the Lectroids named John?
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Hi Guys
John, your post does not relate to the question. I have no interest in discussing loudness here. Please do it elsewhere.
Have fun
Kevin O'Connor
John, your post does not relate to the question. I have no interest in discussing loudness here. Please do it elsewhere.
Have fun
Kevin O'Connor
crossing/post/added content before your plaint
its a public forum - you have to expect naive, unreasonable statements of the "problem" will draw comment - to educate the onlookers even if you are immune to reason
its a public forum - you have to expect naive, unreasonable statements of the "problem" will draw comment - to educate the onlookers even if you are immune to reason
Hi,
that's an interesting Q.
It really seems to me, that no paper has dealt with it.
Sonically a higher Bias differs clearly from lower Bias.
When raising Bias from 0V on there's a quite linearly related rise of SPL too.
Eventually there comes a treshold over which further raise of Bias doesn't lead to more SPL, but rather SPL remains constant.
Its like a kind of saturation effect, which afaik has been mentioned only once in a dutch paper in form of a measurement, but without discussion or evaluation of the reasoning.
All other sources I've read don't mention or ignore it, leaving the impression that any increase in Bias will lead to a linear increase in SPL till flashover. Anyway, with rising Bias in this saturation region sound impression still changes towards a more dynamic more energetic impression.
Impulsive sonic events like a rimshot sound more real, harder, believable.
Its just my gut feeling that this goes together with lower distortion also.
For certain, the higher force per membrane area should not only affect SPL but also distortion positively.
But even if there would be no THD reducing effect within the panel itself, would the increased efficiency allow for lower signal levels feeding into the audio transformer, leading to lower distortion levels from the magnetic circuit.
As efficiency is the key mantra in good panel build, Bias should be cranked up to the highest sensible and practical level.
Under this paradigm the Q of Bias-related THD becomes a non-issue.
jauu
Calvin
that's an interesting Q.
It really seems to me, that no paper has dealt with it.
Sonically a higher Bias differs clearly from lower Bias.
When raising Bias from 0V on there's a quite linearly related rise of SPL too.
Eventually there comes a treshold over which further raise of Bias doesn't lead to more SPL, but rather SPL remains constant.
Its like a kind of saturation effect, which afaik has been mentioned only once in a dutch paper in form of a measurement, but without discussion or evaluation of the reasoning.
All other sources I've read don't mention or ignore it, leaving the impression that any increase in Bias will lead to a linear increase in SPL till flashover. Anyway, with rising Bias in this saturation region sound impression still changes towards a more dynamic more energetic impression.
Impulsive sonic events like a rimshot sound more real, harder, believable.
Its just my gut feeling that this goes together with lower distortion also.
For certain, the higher force per membrane area should not only affect SPL but also distortion positively.
But even if there would be no THD reducing effect within the panel itself, would the increased efficiency allow for lower signal levels feeding into the audio transformer, leading to lower distortion levels from the magnetic circuit.
As efficiency is the key mantra in good panel build, Bias should be cranked up to the highest sensible and practical level.
Under this paradigm the Q of Bias-related THD becomes a non-issue.
jauu
Calvin
Hi Guys
Jauu, thanks for your info and well thought out post.
I would suspect that the subjective impression of transients sounding better past the "electrostatic saturation point" is one of compression being required by our hearing at such loudness - whether the compression is external to us or is our own aural compression makes little difference in protecting our physiology. Otherwise, at tolerable SPLs such sounds would be similar to tape saturation of olde, and other limiting effects that did not have a hard effect.
If a compression effect is occuring then it is inherently increasing distortion. That would support the one THD vs SPL graph that I found from Stax that showed higher THD at 100dB than at 90dB.
I won't be able to make any measurements of my own until January. It will be interesting to test the increase in loudness with bias and see if there is a stop point to that effect as you suggest. If there is, it may be related to the arc-over point and might provide a means to set signals and bias safely in a way to avoid arc over. It might also allow avoidance of the "electronic air cleaner" effect if there is no benefit to having excess bias voltage.
Have fun
Kevin O'Connor
Jauu, thanks for your info and well thought out post.
I would suspect that the subjective impression of transients sounding better past the "electrostatic saturation point" is one of compression being required by our hearing at such loudness - whether the compression is external to us or is our own aural compression makes little difference in protecting our physiology. Otherwise, at tolerable SPLs such sounds would be similar to tape saturation of olde, and other limiting effects that did not have a hard effect.
If a compression effect is occuring then it is inherently increasing distortion. That would support the one THD vs SPL graph that I found from Stax that showed higher THD at 100dB than at 90dB.
I won't be able to make any measurements of my own until January. It will be interesting to test the increase in loudness with bias and see if there is a stop point to that effect as you suggest. If there is, it may be related to the arc-over point and might provide a means to set signals and bias safely in a way to avoid arc over. It might also allow avoidance of the "electronic air cleaner" effect if there is no benefit to having excess bias voltage.
Have fun
Kevin O'Connor
Hi,
I´d say no, because the improved ´attack´ is a parameter/sonic impression which is consistant over the complete loudness range. It for sure is no compression effect of the hearing. Maybe I should have used the term efficiency instead of SPL instead.
jauu
Calvin
I´d say no, because the improved ´attack´ is a parameter/sonic impression which is consistant over the complete loudness range. It for sure is no compression effect of the hearing. Maybe I should have used the term efficiency instead of SPL instead.
jauu
Calvin
I have experimented immensely with (small) ESL drivers and various bias levels and I don't recall any compression effects at any level of operation.
Except, Possibly a few times when the voltage levels applied to the stator's was so high that it was ionizing the air in the gap between the diaphragm and the stator.
I think that the raise in distortion and compression that you are referring to may be because of the way the Stax drivers are constructed.
They have bumper pins that rise above the surface of the stator.
When the diaphragm hits these bumpers then it limits the diaphragms excursion.
This can give a compression effect as the diaphragm still has a little more room to vibrate rather than smashing straight into the stator.
Here is the link a post that has a photo that shows what I am talking about,
http://www.diyaudio.com/forums/plan...t-stax-electrostatic-stators.html#post2722083
In all of my test raising the bias only raises the efficiency of the driver.
This also effectively raises the dynamic range for a given input as well.
I like running them at a higher bias voltage, as it not only raises the sensitivity, But it seems to dampen the diaphragm a little more giving the high impact transients much more authority!!!
FWIW
jer
Except, Possibly a few times when the voltage levels applied to the stator's was so high that it was ionizing the air in the gap between the diaphragm and the stator.
I think that the raise in distortion and compression that you are referring to may be because of the way the Stax drivers are constructed.
They have bumper pins that rise above the surface of the stator.
When the diaphragm hits these bumpers then it limits the diaphragms excursion.
This can give a compression effect as the diaphragm still has a little more room to vibrate rather than smashing straight into the stator.
Here is the link a post that has a photo that shows what I am talking about,
http://www.diyaudio.com/forums/plan...t-stax-electrostatic-stators.html#post2722083
In all of my test raising the bias only raises the efficiency of the driver.
This also effectively raises the dynamic range for a given input as well.
I like running them at a higher bias voltage, as it not only raises the sensitivity, But it seems to dampen the diaphragm a little more giving the high impact transients much more authority!!!
FWIW
jer
Hi Guys
That is an interesting observation, Jer. It seems analogous to having more gain in a circuit than is needed to achieve a required output, allowing relaxed control settings and having a "feel" of greater substance. In those situations the distortion profile changes as well. I think this is what Jauu was aiming at, too.
The formula for the force within the ESL unfortunately says nothing about THD. I'm sure there are some math wizards who may have a thought about that?
It is counterintuitive that certain compression forms actually sound more dynamic.
I won't be able to make my own tests until next month.
Happy Holidays
Kevin O'Connor
That is an interesting observation, Jer. It seems analogous to having more gain in a circuit than is needed to achieve a required output, allowing relaxed control settings and having a "feel" of greater substance. In those situations the distortion profile changes as well. I think this is what Jauu was aiming at, too.
The formula for the force within the ESL unfortunately says nothing about THD. I'm sure there are some math wizards who may have a thought about that?
It is counterintuitive that certain compression forms actually sound more dynamic.
I won't be able to make my own tests until next month.
Happy Holidays
Kevin O'Connor
Hi,
distortions in symmetrical constant charge ESLs are mainly due to mechanical imperfections.
These regard:
- the mechanical tension of the diaphragm (standing waves and non-linear force vs. excursion)
- imperfections in the homogenity of the electrical field (especially in close proximity of the stator plates).
The calculations of the mechanics related distortions are extremely difficult if not impossible to perform.
Typically one can see a strong increase in THD only at lower frequencies where the excursion of the disphragm becomes considerable.
There are no distortion mechanisms in the drive system itself, like heating, BL-modulation, etc. as in dynamic drivers.
As the relationships are perfectly linear, the ESL-drive is free of distortions.
It is quite common, that the audio transformer and driving amplifier add more THD than the Panel itself.
jauu
Calvin
distortions in symmetrical constant charge ESLs are mainly due to mechanical imperfections.
These regard:
- the mechanical tension of the diaphragm (standing waves and non-linear force vs. excursion)
- imperfections in the homogenity of the electrical field (especially in close proximity of the stator plates).
The calculations of the mechanics related distortions are extremely difficult if not impossible to perform.
Typically one can see a strong increase in THD only at lower frequencies where the excursion of the disphragm becomes considerable.
There are no distortion mechanisms in the drive system itself, like heating, BL-modulation, etc. as in dynamic drivers.
As the relationships are perfectly linear, the ESL-drive is free of distortions.
It is quite common, that the audio transformer and driving amplifier add more THD than the Panel itself.
jauu
Calvin
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