AS designs are only intended for low frequencies. The AR 12" crossover was reduced from 1khz in AR3 to 575 hz in AR3a to 200 hz in AR9. Its optimal range is in the lowest few octaves and makes a great subwoofer.
All speakers have many distortion mechanisms. An AS driver should have an extremely compliant surround. The original AR 12" and KLH drivers have cloth surrounds with only a never cure dopant to make it air tight. The displacement of air at maximum excursion is only a small percent of the trapped air, 12mm over an 8" diameter circle compared to 1.75 cubic feet. Therefore P1*V1 = P2*V2 or very close. The force on any given area of the cone at any given time is (Poutside-Pinside)/Area. This is the same for all points on the cone and therefore the pressure differential (gadient) between any two points on the cone is zero. For it to be otherwise the pressure in one point in the enclosure next to the cone would have to be different from the pressure at another point. The design is inherently long throw and a magnet with a long linear region of flux density is required to assure that increases in the applied power are proportional with increases in the applied force over the greatest possible displacement. Measured distortion data bears out the validity of the concept when well executed. 5% at 30 hz on the first commercial design beating every other design by far no matter how large or expensive. That's one reason it became an instant benchmark for others to match or beat.
I didn't need a link telling me what a dome is. 🙄 I was looking for evidence that "a dome tweeter made from paper" (assuming one even exists) doesn't break up as easily as a cone tweeter. That wikipedia page won't help you prove that...
At least along the the axis of cone travel (in and out) a truncated cone is a stronger shape than a curved dome. This is why woofer cones are almost universally conical. On the other hand a conical cone does have problems with spurious bell modes around the edge because its not strong against bending in that axis, although the surround does help control flexing in that direction somewhat.
A curvilinear cone stiffens the cone against bell modes but weakens it in the primary radial axis. (Often used for whizzer cones because they have no surround to stiffen the edge, so there is more need for stiffening against bell modes but less need for strength in the primary axis since the edge is not loaded by a surround) A dome is more akin to the curvilinear cone in that it is curved in both axes.
The problem with the dome though is that when it does go into cone breakup there is no good place for the bending waves to be terminated - they start at the perimeter, travel to the centre and keep going only to reflect off the opposite side. With a conventional cone they originate in the centre and travel outwards, and have the opportunity to be at least partially absorbed at the surround.
Because of this cones can be designed to better control and deal with standing waves than domes. As I said before, a cone design as small as a dome tweeter is not practical, that's why domes are used, not because they're fundamentally superior to a cone as a radiating surface.
Excellent point I hadn't thought of showing why practical details often must trump theoretical ideals. Mechanically a convex dome is much more practical to build, even if its radiation pattern is not quite as good.
The fact that someone went to the trouble of doing it the hard way (concave) suggest that there is some benefit to it though.
5 db down 60 degrees off axis at 15 khz compared to its on axis response. That's AR3a's 3/4 inch dome, Roy Allison's project. Can you find a tweeter that will beat or even equal that? The only one I know of is Allison's later design he used in his own branded speaker systems. Later AR invented ferrofluid cooling to increase power handling but where more output or greater dispersion is needed they can be used in multiples. Unfortunately there are no comparable contemporary designs on the market anyone at CSP has heard of. HiVi Q1R is being used by many as a replacement where necessary but it is clearly inferior. When buying used AR speakers it's best to verify whether or not the original tweeter is installed and whether or not it still functions.
Considering the obsession with edge diffraction phenomena for tweeters I'd think most would shun a concave dome. However I see no theoretical disadvantage to it other than the practicality of manufacturing it due to clearing the magnet at maximum excursion. In principle it doesn't matter whether it's convex or concave. As in Allison's design for his own tweeter the attachment point to drive the dome does not have to be around its outer perimeter edge but could be closer to the center. Modern dome tweeters are not nearly close to a full hemisphere like AR's design, they are only fractional sections of a dome. This difference in geometry explains their poorer dispersion. They do not produce the types of collisions with air molecules near their perimeter that thrust them laterally to the axial direction of the dome's motion.
One of the JBL engineers came in all excited one day. "We need to make our tweeters in a Catenary curve!" It turns out that the Catenary curve is what a flexible line of equally distributed mass drapes to. I think it is the natural curve of the suspension cable of the typical suspended bridge. It is also the shape that a chain hung between two points will form. At first glance it sounds like a great idea: a shape that has a natural and stable curve. If you added equal force along its length (more weight) it would still want to be in the same shape.
Problem is, that is a steady state condition. Go to either end (or both) and give it a sharp rap and you will see a wave travel from side to side. It is not free from time transit issues or standing wave effects.
I don't know if a dome is stiffer than other shapes or not, but I do know that they break into modes, as all structures do, and I have had problems with domes that "went crazy" in the center, buzzing like mad.
David S.
I don't know why you continue to repeat this when I have several times shown you that it is blatantly false. John King at Cletron was the first to try, and held the patent, for the use of ferrofluid in loudspeakers. (United States Patent 4017694). After he showed the worth of it, Ferrofluidics started peddling it around the Boston area, where AR saw it.
David S.
You missed my point all together. I am not arguing that at low frequency the pressure is not uniform over both sides of the cone. The point is that this argument does not apply at high frequency where breakup occurs, assuming that breakup is at frequencies where the wave length is shorter than the enclosure dimensions.
A second point is that even if this uniform, low frequency pressure was superimposed on the cone, it is only present while the driver is reproducing a low frequency. So even if it were to have an effect on breakup it would only have such effect when low frequency content was present in the input signal. A frequency sweep of the driver would show breakup un altered compared to free air.
The third point is that even if at high frequency the pressure were uniform on the back side of the driver when undergoing breakup (which physics tells us it can not be), it is not uniform on the front side.
Fourth, breakup is mostly a function of the cone material density and rigidity (or elasticity) which play a much more dominant role in breakup than the air load. All that is necessary to verify this is to make measurements of a driver in a variety of different size enclosures, and perhaps mounted in a wall, and observed the response in the region of breakup.
Anyway, I have again lost interest in this discussion.
I think anyone who took a course in college calculus and didn't cover hyperbolic trig functions deserves a tuition refund. His math professor didn't earn it.
Hyperbolic function - Wikipedia, the free encyclopedia
"Hyperbolic functions occur in the solutions of some important linear differential equations, for example the equation defining a catenary, and Laplace's equation in Cartesian coordinates. The latter is important in many areas of physics, including electromagnetic theory, heat transfer, fluid dynamics, and special relativity"
The best trained engineers and scientists are not going to be wasting the major portion of their time and talent designing audio equipment. The challenge isn't there. BTW acoustics is an application of fluid dynamics not electrical or electromagnetic theory, the operating fluid being air. Lucky thing for Wallace Sabin.
Hyperbolic function - Wikipedia, the free encyclopedia
"Hyperbolic functions occur in the solutions of some important linear differential equations, for example the equation defining a catenary, and Laplace's equation in Cartesian coordinates. The latter is important in many areas of physics, including electromagnetic theory, heat transfer, fluid dynamics, and special relativity"
The best trained engineers and scientists are not going to be wasting the major portion of their time and talent designing audio equipment. The challenge isn't there. BTW acoustics is an application of fluid dynamics not electrical or electromagnetic theory, the operating fluid being air. Lucky thing for Wallace Sabin.
Thats why I, as a second rate hack, naturally gravitated to it. Whats your excuse?
David S.
The engineering challenge is there, the money isn't.
There are still a lot of really difficult unsolved problems in audio recording and reproduction (some of them perhaps unsolvable) that require real research and engineering skill, however as long as high quality audio reproduction remains a small niche market there isn't the money to attract and sustain a large number of top engineers in the field.
That may or may not change in the future. There are the beginnings of a backlash against the loudness wars over the last few years, perhaps that will raise awareness of sound quality in general and increase the demand for well engineered systems.
That's funny.
I'm retired but have a MS in ME and specialized in fluid mechanics before moving into semiconductor device research. (Funny how electrons in a semiconductor behave like a compressible gas.) If you don't think talented engineers and scientists are involved in acoustics and audio then take a look at active noise cancellation systems. They are used in a lot of military applications, though you may find references hard to find.
Everyone I've known in the industry got started because of a love of music and an overwhelming curiosity about how to do a better job at music reproduction. I've had the pleasure of knowing a lot of brilliant people in this field.
Of course, its all been downhill since the AR and Allison Acoustics days.
David S.
Of course, its all been downhill since the AR and Allison Acoustics days.
David S.
As a former member of ASA (and AIP) myself I know that there are many talented people in acoustics but not in consumer electronics, not even in professional audio systems. Certainly not cutting edge scientists. I expected to go into it myself until my first industrial trade show. Then my eyes were opened wide and I saw a world of excitement that put audio equipment into the perspective it belongs in, children's toys. Fun and an amusing diversion as a hobby but not an adequate challenge given what else is out there.
I'm sure there are people working on acoustic weapons. Work done at Bose Corporation seems to have made large strides in personal noise cancellation. Their $300 product works quite well for plane travel. Those people are hardly the sharpest knives in the drawer though.
Don't know if you are serious about the last comment, but taking the long view of the increase in audio knowledge over the years, it seems the hill has become less steep as most of the important concepts were worked out early on, leaving only smaller, more esoteric details to be worked out.
Even though we are not at the top of the hill yet, it does seem to be more of a plateau in comparison to the cliffs the early audio innovators scaled without the "climbing gear" we take for granted now.
Art
Hey, there are a lot of people in audio because they love it, that could have done other things that paid more.
In one case a fellow I know was pressured to take and turned down astronaut training to support experimental hardware on the shuttle which was based on his invention, that he built major parts of, to pursue audio.
I know for a fact he doesn’t regret it, has never been happier with what he's doing now.
Tom
Here, this guy;
http://www.prosoundweb.com/article/...ploring_the_possibilities_of_audio_technology
In one case a fellow I know was pressured to take and turned down astronaut training to support experimental hardware on the shuttle which was based on his invention, that he built major parts of, to pursue audio.
I know for a fact he doesn’t regret it, has never been happier with what he's doing now.
Tom
Here, this guy;
http://www.prosoundweb.com/article/...ploring_the_possibilities_of_audio_technology
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LOL! The next time you hold an iPod in your hand think about all the iDiots who managed to slap all that junk into a tiny package that does so much, works well, is easy to use and sells for a price that millions can afford. No talent there, for sure.
One example among many.
While the iPod is a miracle of miniaturization allowing you to watch TV one minute, surf the internet the next, play Angry Birds the next, make a phone call, and then listen to MP3s though ear-buds can you tell me what contribution it made to advancing the state of the art in the area of knowlege of high fidelity sound recording and reproduction? IMO none.
Steep? You don't know what steep is. The knowledge of how to store, retrieve, manipulate and amplify electrical signals with predictability and accuracy, and the knowledge of how to build a variety of transducers that don't always create an execrable noise and combine them into something that looks like a relatively non resonant device over 10 octaves when measured on axis in an anechoic chamber gets you to the base camp of Mount Everest. The assault on the summit hasn't even begun yet. Not when you can't even reproduce the sound of say a grand piano or a Stradivarius violin as it would be heard in the same room with you convincingly to just about anyone with normal hearing let alone to critical listeners very familiar with those sounds. The day when you can convincingly reproduce the sound of a symphony orchestra as heard at say Boston Symphony Hall or the sound of a pipe organ and a large choir as heard in a Gothic Cathedral is far into the distant future and way beyond the current state of the art.
Despite far greater advances in imaging technology, the ability to produce very large screen high resolution moving color images in 3D their proponents make no comparable claims. They do not claim to be able to recreate the image of a table or a chair in your room to the degree that you would actually consider making the mistake of sitting in the illusion of the chair or placing something on the image of the table let alone recreating the convincing visual experience of being at the Grand Canyon. The problem with so much ad hype is that many of the people who work at the technology actually begin to believe it themselves.
If and when the high fidelity problem ever yields to people developing radical new concepts that actually advance up towards the summit, they will look down on the best equipment that can be produced today with the same amusement as we would look back on at a hypothetical argument say in the 1930s over who produced the more accurate sounding radio, Crossley or Philco. How do I know? Because I am very familiar with the sound of the real thing and nobody can convince me that a mixture of Welch's grape juce and grain alcohol tastes just like Chateau Lafite Rothschild. It doesn't come remotely close.
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