I tried to find out the effect on the uniformity of the electric field between stators as a function of hole alignment. There were two hole patterns discussed in the Wachara headphone thread, the regular straight alignment and the 'interleaving' alignment where each other row is shifted by 1/2. I tried to model the electric field with this simulator that I found on the web. Here are the results.
First the straight alignment.
and the shifted alignment:
First the straight alignment.
An externally hosted image should be here but it was not working when we last tested it.
and the shifted alignment:
An externally hosted image should be here but it was not working when we last tested it.
Thanks for posting these Arend-Jan. The results look about like what I would have guessed, for whatever that's worth. I guess the question now is how the diaphragm behaves in the two cases. I wonder, for example, whether the diaphragm will be affected by local differences in the acoustic resistances, or whether the stator just looks like a uniform resistance in both cases. The smaller the holes, hole spacing, and diaphragm-stator spacing, the more I would expect the stator to act like a uniformly distributed acoustic resistance. Is that resistance enough to prevent the nonuniform electric field from causing the diaphragm to rattle? I've long assumed that rattling is the "credit card sound" some people have complained about in some designs.
By the way, did you use FEMM or something else to do the simulations?
Few
By the way, did you use FEMM or something else to do the simulations?
Few
Hi Few,
from the looks of it the electric field is more even (the density of the lines is more constant) in the shifted row configuration. With the straight alignment we can clearly see the lines widening and narrowing. The wiggling would be a very small factor, it's the density that counts.
The acoustic resistance will no doubt depend on the frequency. But let's assume that for a given frequency range there is a fluctuation in the acoustic resistance, then my guess would be that it would again be more even in the second case, because the diaphragm is non compressible so we can lump the front and back resistance together. This will give an even distribution in the second case, and a uneven distribution in the first case.
The sim is a Java applet
from the looks of it the electric field is more even (the density of the lines is more constant) in the shifted row configuration. With the straight alignment we can clearly see the lines widening and narrowing. The wiggling would be a very small factor, it's the density that counts.
The acoustic resistance will no doubt depend on the frequency. But let's assume that for a given frequency range there is a fluctuation in the acoustic resistance, then my guess would be that it would again be more even in the second case, because the diaphragm is non compressible so we can lump the front and back resistance together. This will give an even distribution in the second case, and a uneven distribution in the first case.
The sim is a Java applet
Arend-Jan:
I agree the contour density is more important than the wiggling--good point.
With respect to the frequency dependence of the acoustic resistance, most of the dimensions of interest (hole diameter, stator spacing...) are small compared to virtually all the wavelengths being produced by the speaker. That is why I'm inclined to think the stator looks like a fairly pure acoustic resistance--for both the aligned and offset hole configurations. If it's a pure resistance over the frequency range of interest, then there shouldn't be any frequency dependence. I suppose that in some large-hole or large-gap designs there are some stator features that approach one wavelength at 20 KHz or above, but with my aging ears I'm not too concerned about those frequencies.
As a gentle nudge: which software did you use for the simulations?
Thanks,
Few
I agree the contour density is more important than the wiggling--good point.
With respect to the frequency dependence of the acoustic resistance, most of the dimensions of interest (hole diameter, stator spacing...) are small compared to virtually all the wavelengths being produced by the speaker. That is why I'm inclined to think the stator looks like a fairly pure acoustic resistance--for both the aligned and offset hole configurations. If it's a pure resistance over the frequency range of interest, then there shouldn't be any frequency dependence. I suppose that in some large-hole or large-gap designs there are some stator features that approach one wavelength at 20 KHz or above, but with my aging ears I'm not too concerned about those frequencies.
As a gentle nudge: which software did you use for the simulations?
Thanks,
Few
Hi Arend-Jan,
I'll mail a set of new stators to you tomorrow. When you put two stators together, all the holes of one stator will be covered by the no hole area of the other stator. If you flip one of the stators up side down, you will get all the holes of the two stators 100% align with each other. Therefore, you can test the differences between 100% align and 100% non-align.
Please keep us posted on your findings.
Wachara C.
I'll mail a set of new stators to you tomorrow. When you put two stators together, all the holes of one stator will be covered by the no hole area of the other stator. If you flip one of the stators up side down, you will get all the holes of the two stators 100% align with each other. Therefore, you can test the differences between 100% align and 100% non-align.
Please keep us posted on your findings.
Wachara C.
Hi Tosh,
I'm afraid I don't have many details to offer. The coloration description is something I've read in reviewers' comments over the years but it's been so many years it would be almost impossible to track it down by memory.
Then again, there's always Google... I found this example at the InnerSound site. Apparently it comes from the Absolute Sound. I'm pretty sure there are other references to the coloration as well, but this is typical.
"More surprising, at least for me, were the most extended high frequencies, which don't roll-off so sharply and
dramatically as some 'stats (try Martin-Logan's Request or the Quad, old or new). It just keeps on going up, letting air
and a kind of sweet breeziness into the top octave that translates down into bloom and that kind of cream-like sound on
massed violins. Even a small section of violins, if indeed that section has poised intonation. It will surprise no one to learn
that the transients, from the speaker's crossover point of 450 Hz upward, are as good as they come and without that
peculiar, somehow inherent electrostatic credit-card coloration. Instruments being reproduced in the soundspace do not
have that disembodied quality, that lack of palpability that sometimes affects very fast ribbons and 'stats."
By the way, it's not my intention to argue that I've been troubled by the coloration Pearson describes. I'm just suggesting that rattling of the diaphragm because of a non-uniform driving force or insufficient damping might explain such a perception.
Few
I'm afraid I don't have many details to offer. The coloration description is something I've read in reviewers' comments over the years but it's been so many years it would be almost impossible to track it down by memory.
Then again, there's always Google... I found this example at the InnerSound site. Apparently it comes from the Absolute Sound. I'm pretty sure there are other references to the coloration as well, but this is typical.
"More surprising, at least for me, were the most extended high frequencies, which don't roll-off so sharply and
dramatically as some 'stats (try Martin-Logan's Request or the Quad, old or new). It just keeps on going up, letting air
and a kind of sweet breeziness into the top octave that translates down into bloom and that kind of cream-like sound on
massed violins. Even a small section of violins, if indeed that section has poised intonation. It will surprise no one to learn
that the transients, from the speaker's crossover point of 450 Hz upward, are as good as they come and without that
peculiar, somehow inherent electrostatic credit-card coloration. Instruments being reproduced in the soundspace do not
have that disembodied quality, that lack of palpability that sometimes affects very fast ribbons and 'stats."
By the way, it's not my intention to argue that I've been troubled by the coloration Pearson describes. I'm just suggesting that rattling of the diaphragm because of a non-uniform driving force or insufficient damping might explain such a perception.
Few
Hi,
by all means...what are ´inherent electrostatic credit-card colorations´?
I don´t see much difference in the amplitude of variations of the field strength. But the straight aligned stators feature variations symmetrically to a ´centred line´ between the stators while the shifted aligned stators feature asymmetrical field strength variations.
I say I prefer symmetry But let´s see if measurement reveals differences.
jauu
Calvin
by all means...what are ´inherent electrostatic credit-card colorations´?
I don´t see much difference in the amplitude of variations of the field strength. But the straight aligned stators feature variations symmetrically to a ´centred line´ between the stators while the shifted aligned stators feature asymmetrical field strength variations.
I say I prefer symmetry
But let´s see if measurement reveals differences.jauu
Calvin
If memory serves, the original use of "credit card" came from a review of the Acoustats, which indeed use plastic stators. The rattling was generally from wires which were not well-attached- I found that they did indeed tend to pop loose after some usage- and from the less-than-optimal bracing which allowed the stators to flex a bit. With tighter wire adhesion and better frame construction, the rattling and resonant signature of the plastic eggcrate can be minimized, though at the expense of a more obtrusive appearance.
Calvin: You aren't calling into question the reality of something that the Absolute Sound-ers claim to perceive are you?! 
()
Sy: That's interesting. Pearson's claim that the sound is "inherent" in electrostatic speakers would obviously not be supported if the problem turned out to be rattling stators.
Few
()Sy: That's interesting. Pearson's claim that the sound is "inherent" in electrostatic speakers would obviously not be supported if the problem turned out to be rattling stators.
Few
Plastic card coloration
Funny thing this "plastic card coloration", or whatever this is.
In the Esl-63 review the Absolute Sound was very, very precisely about the sound of this coloration
"...The speaker also adds a mild but audible plastic quality to the music it reproduces. This plasticity (quite similar to a bent Visa card, approximately two years of age), is more detectable on some material than on other. Sharp transients, such as those on the Sheffield Drum Record, seem to provoke it. Most electrostats that I have auditioned seem to bespeak their Mylar origins in this manner..."
Also the German Stereoplay magazine (Esl-989 review 9/2004)seems to hear such colorations:
"...Ein Hochgenuß ohne Reue also? Nicht ganz. Der Esl 989 hat eine leichte Färbung - man hört den Kunststoff der Folie. Das allerdings macht er über den gesamten Frequenzbereich, und schon nach kurzer Zeit des Hörens fällt es gar nicht mehr auf..."
Harry
Few said:
Funny thing this "plastic card coloration", or whatever this is.
In the Esl-63 review the Absolute Sound was very, very precisely about the sound of this coloration
"...The speaker also adds a mild but audible plastic quality to the music it reproduces. This plasticity (quite similar to a bent Visa card, approximately two years of age), is more detectable on some material than on other. Sharp transients, such as those on the Sheffield Drum Record, seem to provoke it. Most electrostats that I have auditioned seem to bespeak their Mylar origins in this manner..."
Also the German Stereoplay magazine (Esl-989 review 9/2004)seems to hear such colorations:
"...Ein Hochgenuß ohne Reue also? Nicht ganz. Der Esl 989 hat eine leichte Färbung - man hört den Kunststoff der Folie. Das allerdings macht er über den gesamten Frequenzbereich, und schon nach kurzer Zeit des Hörens fällt es gar nicht mehr auf..."
Harry
Re: Plastic card coloration
"A treat without regret thus? Not completely. The Esl 989 has a light colouring - one hears the plastic of the foil. However it makes over the entire frequency range, and after short time of hearing it is not already noticeable..."
I'm grateful I don't have such discerning ears.
Bablefish translation:harry_at said:
"A treat without regret thus? Not completely. The Esl 989 has a light colouring - one hears the plastic of the foil. However it makes over the entire frequency range, and after short time of hearing it is not already noticeable..."
I'm grateful I don't have such discerning ears.
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