Electrostats vs conventional drivers

This is why you cannot EQ a electrostat in this particular frequency region. The stronger you make the front pressure, the back pressure will be equally as strong. So you can add as many db as you like and you will not gain any bass output at the lower frequency region.

The same is true of a woofer in free air, below a certain frequency the pressure waves diffract around the width of the woofer, and cancel eachother out, increasing low output may give some small boost directly on axis, where the diffraction is negligable, as you see in the dipole graph. But it wont help much or at all if you go low enough in frequency.
 
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This radiation pattern (in the low frequency region) is a characteristic of all dipoles , and exists regardless of line source, point source, or plane.

The geometry of the source does influence the radiation patter at higher frequencies where pressure waves beam in a rectlinear fashion, as opposed to the bass region where they travel more like true waves and exhibit bending around objects.

Further you will have reflections from the back wave which meet the front wave at points in the room forming comb filtering. This also cannot be equalized out, because the time delay cannot be changed electronically, but is a physical characteristic of the room (specifically the path length differences from the source to the listener). Therefore, the only way to reduce those interactions, is with acoustic absorption, or building an enclosure for the ESL.
 
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The reason the response is different at varying distances is partially because of the diffraction from the rear wave to the front (near field , less diffraction ) , and due to the pressure squared fall off as the surface area of the spherical wave increases with distance from the source.
 
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Roger Sanders Electrostatic cook book was a good resource when I built electrostats and derrived the solutions of the damped driven harmonic oscilator from first principles of a spring , and demonstrated that the high frequency response was inversely proportional to the mass of the oscillator back in 2005 at bay area science and engineering fair.

All the cases are covered in this book. Highly recommended.
 
a line source, will radiate energy in a more focused way than a point source, and the fall off in acoustic pressure as a function of distance from the source is actually less for a line source, than point source, because the surface of the wave front has less area. The acoustic energy is spread across a sphere as opposed to a plane, and the surface area of the sphere grows with distance, the surface area of a line source does not grow spherically, but only the plane gets larger in one axis only with distance from the source. This is of course only applicable in mid to high frequency range where sound travels in a straight line from source, and low frequency pressure waves will radiate spherically regardless of the source geometry.

Considering this, your explanation for why ESL have reduced output in the low end , is incorrect and is actually an explanation for why they have greater output in the high end.
 
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a line source, will radiate energy in a more focused way than a point source, and the fall off in acoustic pressure as a function of distance from the source is actually less for a line source, than point source, because the surface of the wave front has less area. The acoustic energy is spread across a sphere as opposed to a plane, and the surface area of the sphere grows with distance, the surface area of a line source does not grow spherically, but only the plane gets larger in one axis only with distance from the source. This is of course only applicable in mid to high frequency range where sound travels in a straight line from source, and low frequency pressure waves will radiate spherically regardless of the source geometry.

Considering this, your explanation for why ESL have reduced output in the low end , is incorrect and is actually an explanation for why they have greater output in the high end.

Read the Baxandall chapter. The effect you speak of gives the membrane mass at low frequencies (via the radiation impedance), which in turn causes the membrane resonance (mass on a spring)- this is the low frequency limit of an ESL. Above this frequency, the SPL is nominally constant with frequency. At frequencies much above the resonance, the membrane is essentially massless.

Remember too that ESLs are a pressure source, not a volume-velocity source like conventional divers - the behaviour is quite different.
 
Cone dipole enthusiasts are almost as intolerable bores as us ESL enthusiasts. Can we all be hard of hearing?

tacit-tactix seems to have seen a diagram in an early chapter of an acoustics textbook. So the poster has concluded that rear waves TOTALLY annihilate the front wave when they meet out of synch. The later chapters might go into how sound from the back bounces around and so its hard to say how much annihilation takes place.

Nobody denies that waves do conflict some, just as the poster says. But then few are building ESL panels targeting bands where that would be a big issue.

While I am no fan of single-cone-driver speakers, some folks seem to like something about their sound and value it above certain other missing virtues. Likewise, the dipole and ESL crowd for our undying love for the features of our speakers.

B.
 
"The explanation for the bass suck-out often heard in ESLs has a more complicated explanation than given by Tacit Tactix, and has nothing to do with the leakage of air from front to back. "

Seems like a pretty specific direct statement that there is no dipole phase cancellation causing the lack of low end to me. And I have shown that it is actually a big part of it, and so has Roger Sanders in his book which I linked. And this is a basic concept anyway.

Maybe try reading more than the first few sentences of the thread ?

In any case, thanks for your input everyone.
 
I actually studied Acoustic MSC at salford, but thanks for your attitude. I dont undestand why people get so snippy in these forums, and attack eachother on a personal level. its dissapointing.
I gather you didn't like that I described your posted statements about acoustics as rudimentary and hidebound to a flawed grasp of real-world room behaviour.

But I will stick with that assessment.... as would the late and great Linkwitz.

B.
 
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this conversation is about ESL , dipoles, phase cancelation, and I actually did describe a little bit of room acoustics.

Please say something useful, specific, or dont make personal comments about people knowledge, or understanding unless you are being constructive. Otherwise why are you here?
 
So many people read a brochure, and talk down to people in forums like they know so much. Another member made a comment about my statement, I defended it in depth, provided references, and explained in plain terms my understanding. That is a lot more than I can say about your post.

What is rudimentary about about my understanding of acoustics? Because from what I can see I have defended the claim without fail. Please respond and enlighten me.
 
Hi Tacit Tactix
I'm sorry if you found my posts offensive, that was not my intention.

Obviously it depends on the extent of your acoustics training, but I would be very surprised if there was any depth to any university paper that might mention ESLs.

ESLs are very different from conventional drivers, they are dipoles rather than monopoles, pressure sources rather than volume velocity sources, and planar sources rather than point sources. The size and cost of ESL means that there has been very little serious science developed around ESLs. What little has been established is very, very different from that now well established lore for conventional drivers. Indeed there remain a couple of huge gaps, things not discussed in any paper or book anywhere.

I started my ESL project more than 10 years ago, and with help from a few people on this site I was able to design and build a sucessful ESL. Beforehand, I did a lot of homework reading books, papers, etc on ESLs. In fact there is very little written about ESLs of any substance, the book by Hunt, the JAES paper by Walker, and the Chapter by Baxandall were pretty much the limit of helpful material. The books by Wagner and Sanders are very limited and occasionally wrong - also I am a professional physicist, so I expect to see equations in support of claims. There is also a lot of folklore about ESL that is wrong, much of it I suspect arises from experiences with overly simple DIY projects.

In the process of building my ESL, I collected a long list of things that I did not understand or did not make sense. A DIYaudio colleague has helped me with some of these things, and we have been working our way through the rest - I've mostly worked on the theory while my colleague, who also has a very good grasp on the maths, works on the measurements to test our mathematical models. We have now published two papers covering two of the five big gaps, and we are currently working on a third. You'll not find any of that material in textbooks, yet. If you send a pm I will be happy to forward copies.

regards
 
Read the Baxandall chapter. The effect you speak of gives the membrane mass at low frequencies (via the radiation impedance), which in turn causes the membrane resonance (mass on a spring)- this is the low frequency limit of an ESL. Above this frequency, the SPL is nominally constant with frequency. At frequencies much above the resonance, the membrane is essentially massless.

Remember too that ESLs are a pressure source, not a volume-velocity source like conventional divers - the behaviour is quite different.

According to Walker's equation, in the far field, for frequencies above resonance and below the point where membrane mass causes treble loss, SPL is constant with frequency under constant current drive. That means that voltage has to increase with 20 dB/decade with decreasing frequency. As almost no-one seems to realize that, it is hardly surprising that many ESLs have insufficient bass.

Mind you, you are in the far field when the distance to the loudspeaker is great compared to lamda/(2 pi) and the path length differences from different parts of the loudspeaker to your ears are much smaller than a wavelength. For high audio frequencies and practical listening distances, that last condition can only be met with segmented stators and some sort of crossover. (The damped transmission line in the ESL-63 is actually a sort of crossover; at high frequencies, only the centre of the ESL-63 makes sound.)

See Elektrostatic Loudspeakers
 
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