Many thanks to Lynn Olson for a tone-perfect if quick romp through the technologies. I'd only quibble with the depiction of ESL efficiency as low; except for direct-drive high voltage amps, the general process of driving ESL is cumbersome but not inefficient in the usual sense of watts-in to watts-out.
Also, and appropriate to this thread, is the peculiar fact that despite the long historic effort to enclose music systems in feedback, it has stopped (for very challenging reasons) at the awful loudspeaker end*. Some of the hottest discussions at this forum are in new efforts at motional feedback esp. with DSP.
Ultimately, the problems Lynn Olson outlines boil down to matching impedances of the thinness of air and the heaviness of most human-made materials, plasmas excepted.
Thin films go a long way to help but, as Lynn Olson says, the mechanisms for driving membranes today are weak (at least relative to the limits of arcing in domestic air or the force at a distance of plane magnets) and therefore require "suspensions" that are unable to simultaneously achieve the motions needed at lowish frequencies or the dispersions at highish frequencies.
So back to the question. I'd say waving heavy cones of cardboard to create sound using cumbersome motors - in the absence of motional or any other kind of feedback loop - is certainly a dead-end technology. My guess is the future is likely to be in some kind of self-propelled film (think piezo-electric), as has recently been announced.
Ben
*and the mic end too..... interesting that the great mics are membranes... anybody measuring their speakers with a cone mic?
Also, and appropriate to this thread, is the peculiar fact that despite the long historic effort to enclose music systems in feedback, it has stopped (for very challenging reasons) at the awful loudspeaker end*. Some of the hottest discussions at this forum are in new efforts at motional feedback esp. with DSP.
Ultimately, the problems Lynn Olson outlines boil down to matching impedances of the thinness of air and the heaviness of most human-made materials, plasmas excepted.
Thin films go a long way to help but, as Lynn Olson says, the mechanisms for driving membranes today are weak (at least relative to the limits of arcing in domestic air or the force at a distance of plane magnets) and therefore require "suspensions" that are unable to simultaneously achieve the motions needed at lowish frequencies or the dispersions at highish frequencies.
So back to the question. I'd say waving heavy cones of cardboard to create sound using cumbersome motors - in the absence of motional or any other kind of feedback loop - is certainly a dead-end technology. My guess is the future is likely to be in some kind of self-propelled film (think piezo-electric), as has recently been announced.
Ben
*and the mic end too..... interesting that the great mics are membranes... anybody measuring their speakers with a cone mic?
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The circumstances aren't always the same though. Why would I worry about lobing out at 60 degrees when the constrained sources radiate to 30 degrees?
As someone who has experimented with most known forms of transduction, I would not hold my breath waiting for something to replace a conventional cone loudspeaker.
Mics need not have any efficiency to speak of, so they can be small and light. Ever try playing your stereo back though a Mic? All mics are reciprocal, so its doable.
Guess I'm just a goofy optimist. Esp about the new stuff I mentioned. If anybody could make a safe, functional, full-range plasma speaker, we'd have no other kind in audiophile homes; a judgment I believe that would be shared by those familiar with Ionovac tweeters.
Well, I do play through a mic and I am not "holding my breath" since I have played most of my sound by ESL for the past 35 years. Pretty darn rare for anybody who likes ESLs to willingly return to cone drivers*.
Perhaps Canadians have more ESLs by our resident genius, Dayton-Wright and from Mother England's Quad, plus the enthusiasm for ESLs in Holland.
Speaking of mics, both Lynn Olson and I forgot to mention electret technology (which just coincidentally was developed by a buddy while I was at Bell Labs in Murray Hill). I posed the electret question a few weeks ago and was assured it doesn't model well for speakers.
Ben
*Some owners might say something similar for big folded bass corner horns too
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Ok, first, which constrained source are you talking about and at what frequency is it radiating at 30 degrees? Most sources will have different dispersion patterns at different frequencies based on their physical size.
Second, is this a trick question? This is a lot like saying "Why would I worry about getting hurt in a (single car) car accident, my car can only go 2 mph?"
If your source can only radiate into 30 degrees you obviously don't need to worry about what's going on at 60 degrees, but how is a source that can only cover 30 degrees acceptable in the first place? (I'm assuming we're talking about mid frequencies in a regular domestic environment and system here, there are uses for a limited 30 degree coverage but not usually in the midrange frequencies in a living room.)
Third, if you are competently setting up a system you should be at least vaguely aware of where your lobes are pointed and how wide they are. In fact all of this should be addressed in the design stage before the source is even constructed. Any decent crossover simulator will let you move your virtual mic in 3 axes to see what your dispersion and lobes will look like.
Measuring with a mic and correcting with eq or dsp IS a feedback loop. And it's generally adequate as long as you keep the system within it's linear boundaries, you design the system so that it doesn't have issues that can't be corrected with eq or dsp, and you are reasonably aware and proactive of the effects the room has on the system.
I'd say "waving heavy cones of cardboard to create sound using cumbersome motors" is not an accurate reflection of the state of the art in moving coil drivers. Clearly you don't like your own speakers but I wouldn't describe mine that way, not even the cheap ones. And they won't be a dead end technology until something better comes along. Something better is probably going to be a point source that can play the entire audible range (and probably more than the audible range) at reference level and can change it's size and shape (and the size and shape of the listening room) to correspond to the media signal. Something like the Holodeck on Star Trek. Don't hold your breath. Until then all we have is incremental improvements as technology allows. But even so the current state of the art is very good.
Most acceptable deficiencies?
What your priorities are over which deficiencies in speaker technology are most acceptable depends on many things.
None of Piezo, Moving Coil, Electrostatic Transducers has ever been abandoned in the market since they where first released.
I take your above comment in terms of monitoring speakers, rather than by other constraints.
Ben though I suspect was thinking of monitoring speakers and forgets that not everyone wants monitors with the compromises his have and did not make it clear he meant for him, and I suspect he does not think 3$ moving coil speakers will not remain cheaper to manufacture than his home system.
If your talking exclusively about a truly revolutionary better technology in all respects, then you are correct, but for Ben I suspect he cares little about what his speakers do wrong compared to what they do right relative to other speakers.
I bet since Bens system is an electrostatic system it does some things better than any moving coil system, just because it uses an appropriate and different conventional technology. I also bet his electrostatic speakers do so some things worse than some moving coil systems. Incidentally Electret (a close relative to electrostatic) is the most common tech for Microphones.
* The Square wave performance of any well designed electrostatic speaker (within bandwidth) is unmatched by any moving coil speaker regardless of cost.
I wont go in for saying which of these areas is unquestionable better in good examples of moving coil or electrostatic technology, as I am sure all who have listened to good examples of both electrostatic and moving coil speakers can tell you:
* Minimum production cost.
* Stereo matching / reproducability.
* Omni directional nature.
* Lowest frequency available.
* Bandwidth.
* Size.
* Maximum output volume.
* Portability.
But holding other factors still, it is clear that in some areas both of these two VERY old technologies clearly are in a different league from the other, which is the most acceptable deficiencies is a matter for taste.
I think any HiFi DIY enthusiast should at least hear Electrostatic Speakers, as the things electrostatic speakers do well, show how bad moving coil speakers are at these things.
Likewise moving coil speakers will never be abandoned completely because they do some things better than electrostatics.
If I could imagine a future tech which has all the benefits of Electrostatics speakers and the Benefits of Moving coil speakers, it would be great, but I suspect it will be very hard to get this.
Lets hope one day something like a perfect speaker wallpaper, with bass, reproducability, stereo imaging, low distortion, great square wave performance, and low cost, that beats moving coil and electrostatic speakers in all both techs strengths.
What your priorities are over which deficiencies in speaker technology are most acceptable depends on many things.
None of Piezo, Moving Coil, Electrostatic Transducers has ever been abandoned in the market since they where first released.
I take your above comment in terms of monitoring speakers, rather than by other constraints.
Ben though I suspect was thinking of monitoring speakers and forgets that not everyone wants monitors with the compromises his have and did not make it clear he meant for him, and I suspect he does not think 3$ moving coil speakers will not remain cheaper to manufacture than his home system.
If your talking exclusively about a truly revolutionary better technology in all respects, then you are correct, but for Ben I suspect he cares little about what his speakers do wrong compared to what they do right relative to other speakers.
I bet since Bens system is an electrostatic system it does some things better than any moving coil system, just because it uses an appropriate and different conventional technology. I also bet his electrostatic speakers do so some things worse than some moving coil systems. Incidentally Electret (a close relative to electrostatic) is the most common tech for Microphones.
* The Square wave performance of any well designed electrostatic speaker (within bandwidth) is unmatched by any moving coil speaker regardless of cost.
I wont go in for saying which of these areas is unquestionable better in good examples of moving coil or electrostatic technology, as I am sure all who have listened to good examples of both electrostatic and moving coil speakers can tell you:
* Minimum production cost.
* Stereo matching / reproducability.
* Omni directional nature.
* Lowest frequency available.
* Bandwidth.
* Size.
* Maximum output volume.
* Portability.
But holding other factors still, it is clear that in some areas both of these two VERY old technologies clearly are in a different league from the other, which is the most acceptable deficiencies is a matter for taste.
I think any HiFi DIY enthusiast should at least hear Electrostatic Speakers, as the things electrostatic speakers do well, show how bad moving coil speakers are at these things.
Likewise moving coil speakers will never be abandoned completely because they do some things better than electrostatics.
If I could imagine a future tech which has all the benefits of Electrostatics speakers and the Benefits of Moving coil speakers, it would be great, but I suspect it will be very hard to get this.
Lets hope one day something like a perfect speaker wallpaper, with bass, reproducability, stereo imaging, low distortion, great square wave performance, and low cost, that beats moving coil and electrostatic speakers in all both techs strengths.
Lot of smart thought in owenhamburg's post. Thanks.
For sure we all use Rice-Kellogg drivers and there's no good substitute today. At least I ran motional feedback amps with my sealed box and horn woofers for several decades to dramatically clean them up.
But a moment's thought at the complexity and cost of producing a quality cone driver and the limitations of the concept show it is a dead-end technology for the future. I had a Jaguar with reciprocating armature fuel pump (from Lucas.... of course). Anybody think, even in 1960, that that was a sane approach compared to a rotary pump?
Funny you should mention "speaker wallpaper":
http://www.diyaudio.com/forums/planars-exotics/240162-if-you-had-lot-esl-panels.html
Ben
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Absolutely. In the sweet spot it should be capable of stunning performance. The problem is the sweet spot will be very small due to massive lobing problems caused by the extreme distance between the mid and tweeter and the horribly narrow dispersion of a 1 meter wide mid. But if you limit the audience to one person that can sit very still and eq the sub to give at least reasonably flat response it's probably very nice. But as others have mentioned, multiple speakers with multiple drivers playing the same frequencies can only truly integrate at one single point in space, especially when the drivers are massively oversized wrt the frequencies they are responsible for.
The issue here though is that he wants it to sound like a live performance down the hall and around the corner in another room. I don't think that's going to happen. You can have some things some of the time but you can't have everything all the time.
I believe Danley has stated that his Synergy horns can do square waves quite well. I've never investigated this claim in any depth but at this point I see no reason to doubt it. (These horns use moving coil drivers in a clever way to make them a truly point source integrated design.)
Indeed "beaming" is a hudge problem with non segmented Electrostatic loud speakers (ESL).
My Quad ESL 57 speakers could only have one person experience a good stereo sound at a time and speaker position was critical and difficult to get right without practice (or two people), and moving the speakers to fit your position. With segmentation, my Quad ESL 63 speakers can support 3 people on a sofa, which is still terrible compared to a multiway moving coil speaker. Your points are valid, multi way Moving coil speakers have much wider sweet spots, which is why my ESL 63's are mounted on rotating plinths. Also 90' off axis you get almost no sound in free space for dipole speakers and ESL's due to the week nature of Electrostatic Forces have to be dipoles.
I agree. For HiFi with a good performance and a good recording at home I wont go back to Moving coil speakers, but for a party, or background music I would not consider an Electrostatic design for anything other than a tweeter. For portability I think an ESL speaker is impractical but STAX have attempted this more than once for headphones.
Have a look at this third party measurement of the Quad ESL 63 by stereophile.com for a square wave.
The image is also attached.
In my experience in the right position a good ESL will amaze anyone who has never heard them before, without exception, then they will say how they sound amazingly lifelike, and how the stereo imaging is unlike anything they have ever heard before from speakers, and the next comment will be how they are so BIG! Typical first next comment is could live with such big speakers? Can they have smaller electrostatics?
Yes I agree with the opinion "Loudspeaker technology is truly primitive" both for ESL and moving coil speakers, and wonder genuinely if the best solution has not yet been found.
Attachments
As far as I know piezoelectric speakers cant typically displace enough air for lower audio octaves, so in Air are only used for high frequencies.
Moving coils are not just common because they are cheaper to manufacture than all speakers but piezoelectric transducers, but they do some things very well, like portability, and flexibility in size.
Electrostatic speakers are not as good as moving coils for some things and better for others.
Moving coils are not just common because they are cheaper to manufacture than all speakers but piezoelectric transducers, but they do some things very well, like portability, and flexibility in size.
Electrostatic speakers are not as good as moving coils for some things and better for others.
Ben, I once embarked on a DIY plasma tweeter/electrostatic mid (4' tall panels) project. I completed one tweeter (direct driven like yours were), and I found that the mass issue wasn't giving anything like what I expected. They sounded too much like any good tweeter.
I stopped because of the other less practical issues, including that I didn't want the electrostatic to be dipole. The larger source was the other overall difference and I figured it could be had with horns, and yes I'm of the mind that they can achieve the same goals I was looking for.
I once bought a car that can only do 2mph for my children. A 30 degree vertical half angle isn't uncommon in a domestic situation. Why should it be an issue whether it's treble or midrange?
All I said was roughly, "THINK piezo-electric".... because I didn't think many folks would know about the new graphene driver. Maybe it has promise and maybe not. Tell us your thoughts. Here's a link to the MIT-ezine:
First Graphene Audio Speaker Easily Outperforms Traditional Designs | MIT Technology Review
BTW, my mid ESLs are mounted on a section of a sphere corresponding to a point-source origin. Go model that.
AllenB - great to learn of your experiment with plasma. Brave man - braver to deal with invisible poison gas than with lethal current HV ESLs! A buddy had an Ionovac system and I can picture the listening experience in my head even today. But truth be known, and maybe like Italian pasta dishes, not hard to make a passible tweeter in a variety of ways today.
Ben
First Graphene Audio Speaker Easily Outperforms Traditional Designs | MIT Technology Review
BTW, my mid ESLs are mounted on a section of a sphere corresponding to a point-source origin. Go model that.
AllenB - great to learn of your experiment with plasma. Brave man - braver to deal with invisible poison gas than with lethal current HV ESLs! A buddy had an Ionovac system and I can picture the listening experience in my head even today. But truth be known, and maybe like Italian pasta dishes, not hard to make a passible tweeter in a variety of ways today.
Ben
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Sure. A carburettor is regulated in surplus by holding pressure behind the float valve, and in starvation by the capacity of the fuel bowl.
Do you think that cone speakers would be used under compression if the motors didn't have a little extra to offer?
You didn't say half angle, you just said 30 degrees.
"Why would I worry about lobing out at 60 degrees when the constrained sources radiate to 30 degrees?"
And it all depends on your dispersion goals and the frequency that's it's radiation equals 30 degrees.
It's a big issue because we generally want a smooth dispersion curve (no bumps or mushroom clouds) and if it's not flat we want it steadily and smoothly decreasing as frequency increases.
Here's the whole issue in pictures.
Pic 1 - a couple of random .frd files, the blue is a woofer, red is a tweeter and black is summed response. Diameter of midrange is 999 mm, diameter of tweeter is 300 mm. No crossover applied except a resistor on the tweeter to roughly level match spl.
Pic 2 - I designated the vertical offset between drivers as 60 cm. Note the drastic changes in the crossover region (and beyond) in the summed response. You can't fix this with eq as you will see.
Pic 3 - A view of response off axis 2.86 degrees horizontally. The blue line moves more than the red line at 3200 hz, that's a function of it's massive size vs the frequencies it is responsible for. The mid is down 3db already at 3200 hz at less than 3 degrees off center.
Pic 4 and 5 - 14.04 and and 28.81 degrees off axis horizontally.
An externally hosted image should be here but it was not working when we last tested it.
If you think the horizontal off axis is bad you don't want to see the vertical. Very small changes make devastating differences.
As you can see, the amplitude and even the frequency of the peaks and valleys change as you move around off axis even a few inches, so there's no way to fix these problems with eq or dsp.
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That's one thing I can't model. I'm not sure if Akabak is capable of this or not. BUT I hardly think it matters much. I saw pics of this speaker on the internet and it isn't very thick so it's not curved much.
The problems shown above are the reason Keele went with his CBT curved array but I don't think he achieved much without also progressively shading the drivers. A large percentage of the drivers in the CBT array are shaded and I think the topmost drivers were heavily shaded. Also, Keele's array had very small center to center distances, probably around 2.5 inches. So there are ways to deal with these issues but a small amount of curve on the mid driver isn't going to do much.
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There seems to be something wrong with that software package or how it is being used. EG: the red and blue traces in the first two plots seem identical. Perhaps they use a single FRD shot and the offset is simulated? If so where does the listening position change during this? If it were a simple and symmetrical distance calculation where would the response variations be coming from.
(P.S the charts seem to have changed since I started posting but I can't see what has changed anymore)
(P.S the charts seem to have changed since I started posting but I can't see what has changed anymore)
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