Electrostatic speakers?

[andreasmaaan]

I think the Barefoot MM12 does this as well as anything I've heard and the Apogee Stage captures a good deal of the vivid tone-colours I'm searching for (albeit with a "silvery" overlay to the sound). And, believe it or not, the much-maligned KRK monitors do a remarkably decent job in this area (though not in others). The flat honeycomb speakers Sony and Technics made years ago were likewise very good at timbre (though once again poor in other respects). And the ancient Stax SR-XIII headphone was very good at getting tone-colours right, far far better than any of the later Stax models (although I haven't heard the Omega line). But all my other speakers fail to a greater or lesser extent in conveying the tonal allure of beautiful instruments.

That's interesting. The MM2 has more in common with the JBL you mentioned earlier, while the Apogee is a different beast. All three (less so the Apogee) are quite neutral speakers.

KRK monitors also tend to be fairly neutral box monopoles.

My guess is that the ability to capture timbre realistically has very little to do with FR but has more to do with being able to faithfully reproduce ALL the very low-amplitude harmonics that make real instruments sound as they do.

Can you explain this a bit more? Specifically, what do you mean by "faithfully"?

 

[richard12511]

I agree with the perception, that the best panel speakers portray the timbre of acoustic instruments in a more lifelike way than the best conventional dynamic speakers. Most noticeably with piano, but also with voice and other instruments. Whether that is due to having low distortion (thus preserving the instrument harmonics captured in the recording), having flat FR, or some other reason, who knows?

I doubt it's distortion, since many cone and dome loudspeakers have distortion levels that are already below the limits of human hearing.

My guess is that it has more to do with the typically narrow dispersion pattern.

 

[T.J. McKenna]

Couple of quotes from Wiki

In virtually all electrostatic loudspeakers the diaphragm is driven by two grids, one on either side, because the force exerted on the diaphragm by a single grid will be unacceptably non-linear, thus causing harmonic distortion. Using grids on both sides cancels out voltage dependent part of non-linearity but leaves charge (attractive force) dependent part.[1] The result is near complete absence of harmonic distortion. In one recent design, the diaphragm is driven with the audio signal, with the static charge located on the grids


Advantages Edit

Advantages of electrostatic loudspeakers include:

levels of distortion one to two orders of magnitude lower than conventional cone drivers in a box[citation needed]
the extremely light weight of the diaphragm which is driven across its whole surface
exemplary frequency response (both in amplitude and phase) because the principle of generating force and pressure is almost free from resonances unlike the more common electrodynamic driver.

This is the "standard" blahblahblah "explanation" you get whenever any "expert" gives his recycling of the "why ESLs are so much better" theory. It is NEVER their own research but is simply repeating what they've read somewhere else. And yes, at low levels (much lower than most live music) ESLs have distortion in the midrange and treble at amplifier-like levels. But then so do many modern dynamic drivers: for instance, my 15 year-old JBL LSR6328s, when paired with the LSR6312 sub, have below 0.5% at all frequencies above 60Hz at 96dB/1 metre. At the SPLs ESLs are typically played at I'd imagine it'd be considerably lower.

 

[andreasmaaan]

I doubt it's distortion, since many cone and dome loudspeakers have distortion levels that are already below the limits of human hearing.

Perhaps at moderate levels, but not at realistic (i.e. instruments in the room) levels. But of course the same must be said of electrostats.

 

[Blumlein 88]

Couple of quotes from Wiki

In virtually all electrostatic loudspeakers the diaphragm is driven by two grids, one on either side, because the force exerted on the diaphragm by a single grid will be unacceptably non-linear, thus causing harmonic distortion. Using grids on both sides cancels out voltage dependent part of non-linearity but leaves charge (attractive force) dependent part.[1] The result is near complete absence of harmonic distortion. In one recent design, the diaphragm is driven with the audio signal, with the static charge located on the grids


Advantages Edit

Advantages of electrostatic loudspeakers include:

levels of distortion one to two orders of magnitude lower than conventional cone drivers in a box[citation needed]

I think maybe one order of magnitude is closer to the truth. You can see some measures Ray has made of his ML's

the extremely light weight of the diaphragm which is driven across its whole surface
exemplary frequency response (both in amplitude and phase) because the principle of generating force and pressure is almost free from resonances unlike the more common electrodynamic driver.

 

[T.J. McKenna]

That's interesting. The MM2 has more in common with the JBL you mentioned earlier, while the Apogee is a different beast. All three (less so the Apogee) are quite neutral speakers.

KRK monitors also tend to be fairly neutral box monopoles.



Can you explain this a bit more? Specifically, what do you mean by "faithfully"?

The fact that widely disparate designs do timbre well while more closely convergent ones often don't suggest something else is at work here.
As for "faithfully" I suppose I mean "accurately". In all respects, not just FR. Timbre is predominantly harmonics, which are complex and also tend to be a lot lower in amplitude than the fundamental. My hypothesis is that some speakers don't transmit all of these harmonics accurately, that they either "smooth" them over, or "smear" them, or possibly don't reproduce them at all. I believe measuring this phenomenon would be a matter of sending a harmonically complex signal (of, say, a trumpet) through the speaker and comparing every single harmonic in both amplitude and the time-domain between input and output. Not a good "scientific" explanation, I know, but then I'm no scientist.

 

[MRC01]

I doubt it's distortion, since many cone and dome loudspeakers have distortion levels that are already below the limits of human hearing.

My guess is that it has more to do with the typically narrow dispersion pattern.

Perhaps for electrostats that produce treble from a large panel. But Maggies have a long (5' or so) vertically oriented ribbon tweeter that crosses from the panel around 1700 Hz. The tweeter dispersion should resemble a line source, which is wide and even.

At 1700 Hz the wavelength is about 7 or 8 inches and the panel is wider than that. So it likely has uneven dispersion in these upper midrange frequencies just below the tweeter crossover.

 

[Wes]

I believe the speed is lack of bass and lack of resonance from a box.

Sure. I have a similar belief. I'd like something more tho.

 

[andreasmaaan]

As for "faithfully" I suppose I mean "accurately". In all respects, not just FR. Timbre is predominantly harmonics, which are complex and also tend to be a lot lower in amplitude than the fundamental. My hypothesis is that some speakers don't transmit all of these harmonics accurately, that they either "smooth" them over, or "smear" them, or possibly don't reproduce them at all. I believe measuring this phenomenon would be a matter of sending a harmonically complex signal (of, say, a trumpet) through the speaker and comparing every single harmonic in both amplitude and the time-domain between input and output. Not a good "scientific" explanation, I know, but then I'm no scientist.

Ok, but a flat frequency response is precisely how we know that all the harmonics on a recording are reproduced at the same amplitude relative to the fundamental. There's no need to use a complex signal to measure this; in fact this would just make it unnecessarily difficult.

Ditto with the time relationship: it is very easily measured, to a very high level of accuracy, with standard test tones.

And ditto also with nonlinear distortion.

The reason we use specialised test tones to measure these things is accuracy and efficiency. There is nothing to be gained by using some other non-specialised signal.

The fact that widely disparate designs do timbre well while more closely convergent ones often don't suggest something else is at work here.

I don't think so. The KRKs and the JBLs are similar in the sense they are two-way box monopoles, but their frequency responses and (particularly) their off-axis radiation are different enough that you would expect them to have subjectively different tonality (speaking generally about KRKs here of course, as I don't know which specific model you're referring to).

 

[Wes]

So you're saying that nothing exists unless we can measure it?...

some have said that nothing exists until you measure it - but that was for things smaller than speakers

 

[30 Ounce]

Measurements of Quad ESL’s. Distortion and step response are both very good.

http://www.troelsgravesen.dk/QUAD-2812.htm

 

[andreasmaaan]

Measurements of Quad ESL’s. Distortion and step response are both very good.

http://www.troelsgravesen.dk/QUAD-2812.htm

Distortion is ok, but no better than decent dynamic speakers (keeping in mind the measurement is taken at the reletively gentle SPL of 86dB/1m).

There are certainly many dynamic speakers out there with significantly lower distortion. Here for example is a Revel M106 at the same SPL. Distortion is far better than the QUAD above 200Hz:

 

[MRC01]

I believe the speed is lack of bass and lack of resonance from a box.

I doubt it ["fast" sound] is lack of bass, as the big panel speakers have flat bass response down to 30-40 Hz and they still have that "fast" sound of the smaller panels which do lack bass.
So I suspect it's related to something else... perceptually, subjectively, it sounds like clean mids free of resonances, but impressions can be deceiving, it could be something else, perhaps the dispersion pattern, more direct less reflected.

 

[richard12511]

Perhaps at moderate levels, but not at realistic (i.e. instruments in the room) levels. But of course the same must be said of electrostats.

Yeah I was assuming moderate levels. Realistic sounding volume is another matter, and electrostats are probably some of the worst when it comes to realism on that front. Live instruments are really loud at the distances of typical home listening. The JTRs are good for when I want that live volume sensation, but even then, I doubt they can keep up with real drums.

 

[richard12511]

Perhaps for electrostats that produce treble from a large panel. But Maggies have a long (5' or so) vertically oriented ribbon tweeter that crosses from the panel around 1700 Hz. The tweeter dispersion should resemble a line source, which is wide and even.

At 1700 Hz the wavelength is about 7 or 8 inches and the panel is wider than that. So it likely has uneven dispersion in these upper midrange frequencies just below the tweeter crossover.

Do you know of any measurements of the bigger Maggies that show this dispersion width?

 

[richard12511]

perhaps the dispersion pattern, more direct less reflected.

This is exactly what I said, and you disagreed with me

We know that frequency response and dispersion are the two most important factors of a loudspeakers sound, by far, so the "speed" most likely has something to do with one of these two things. In my mind, the narrow dispersion(less reflected sound) seems the more likely.

 

[30 Ounce]

Distortion is ok, but no better than decent dynamic speakers (keeping in mind the measurement is taken at the reletively gentle SPL of 86dB/1m).

There are certainly many dynamic speakers out there with significantly lower distortion. Here for example is a Revel M106 at the same SPL. Distortion is far better than the QUAD above 200Hz:

View attachment 105686

His graph is off...he has the FR starting at 98db and average about 96db so that distortion is about 10 db lower. Not sure what equipment he used to measure but it may be the limit of his equipment.

I agree with you there are cone, dome, ring and compression drivers with really low distortion. They need crossovers which introduce phase shift and time alignment problems. Those can be overcome as well. That step response is almost perfect.

 

[andreasmaaan]

His graph is off...he has the FR starting at 98db and average about 9db so that distortion is about 10 db lower. Not sure what equipment he used to measure but it may be the limit of his equipment.

Actually no, the graph is correct. SPL is arbitrary (measurement is taken at 5mm and is uncalibrated). Distortion is expressed as a percentage (see right-hand y-axis label):

And he states:

Distortion measured with microphone 5 mm to front in middle of panel @ 2.8V, equivalent to around 85-86 dB @ 1 meter, 2.8V.
Green = 2nd harm., orange = 3rd harm.

 

[NTK]

Couple of quotes from Wiki

In virtually all electrostatic loudspeakers the diaphragm is driven by two grids, one on either side, because the force exerted on the diaphragm by a single grid will be unacceptably non-linear, thus causing harmonic distortion. Using grids on both sides cancels out voltage dependent part of non-linearity but leaves charge (attractive force) dependent part.[1] The result is near complete absence of harmonic distortion. In one recent design, the diaphragm is driven with the audio signal, with the static charge located on the grids


Advantages Edit

Advantages of electrostatic loudspeakers include:

levels of distortion one to two orders of magnitude lower than conventional cone drivers in a box[citation needed]
the extremely light weight of the diaphragm which is driven across its whole surface
exemplary frequency response (both in amplitude and phase) because the principle of generating force and pressure is almost free from resonances unlike the more common electrodynamic driver.

The story sounds nice, but reality is quite different.

How accurately do you think you can suspend a very thin diaphragm perfectly centered between two plate electrodes? How uniform do you think the thickness and other material properties of the diaphragm are? Is there any residual stress in the diaphragm from its forming operation? Is the diaphragm uniformly tensioned? How uniform is the deposition of the conductive layer, which determines the uniformity of the electrical conductivity of the diaphragm, and therefore the electric field and the electrostatic force. Any of these will result in the diaphragm not moving in a flat plane.

Here are FR plots of 4 different speakers from a well known speaker comparison test. See the resonances in speaker M? Want to guess what type of speaker it was?

 

[MRC01]

This is exactly what I said, and you disagreed with me
...

I didn't intend to give that impression. I was pointing out that the dispersion pattern between Maggies having a ribbon tweeter should be significantly smoother than an electrostat (at least in the treble), yet the Maggies still have that "fast" sound (whatever "fast" means, like justice Potter Stewart I can't necessarily define it but I know it when I hear it).