What an interesing thread this is. We appear to have a habit of making simple ideas far too easy to grasp. This is apparently not a good idea, but what the hell I think I will just go with what feels right.
Last edited:
I don't know anyone else in audio who has these texts. That seems obscure to me.
You can also get the set used on Amazon for a good price. I bought a pristine copy of Morse Vibration and Sound for about $20 on Amazon. And it even turned out to be a first addition.
As much as I enjoyed these texts when I was in school I would not recommend them to a physics student today. The modern approach to physics using tensors, etc. is so much more elegant. This was only lightly touched on by Morse, but is now the established basis of modern Physics and space-time. Maxwell's equations become a single simple one term equation like Einstein's tensor equation for gravity.
To me, the next breakthrough in "horn theory" will be when someone formulates the problem in tensor form. That would allow for a huge step in understanding with an appropriate simplification of the equations. To do the problem now in three separate orthogonal coordinates is a major PITA. With a tensor formulation and a modern computer the ideal waveguide for any arbitrarily specified input and output could readily be obtained with simple numerical procedures. Like Einstein, who saw the future of physics (as discrete rather than continuous) late in life but was too old to actually pursue it because the math was too hard, I too will have to wait for someone else to carry this torch.
Thanks for the backstory on JBL and FoMoCo. It's remarkable how talented Fortune 500 companies are at avoiding paying original inventors for intellectual property, while making sure to collect every cent from licensees.
Makes me less sympathetic about them whining how the big bad Chinese are stealing their IP, when they do everything they can to avoid paying inventors what they are due. Same story in the music biz, which is notorious for funny-money accounting.
People forget that in the 19th Century, the USA did the same thing for writers and inventors over in Europe ... stole everything they could. Does this excuse Chinese theft of IP? No, but the Fortune 500 aren't exactly white hats, either.
I really appreciate Dr. Geddes coming forward; it's hard to establish priority in the audio biz, thanks to a blizzard of corporate PR over many decades, and it's important to get the names of the real engineers and physicists who did the heavy lifting.
Last edited:
Ok then seriously, does anyone know if a patent was ever issued for the flat speaker baffle board? This is a serious question. I have for example, a set of Peavey FH-1 folded horn cabs. This is nearly identical to the Klipsch LaScala design, yet as far as I can tell it was not licensed and it is fairly complex. Looking back through Peavey patents I do see some very familiar looking things that have popped up later but I can't find the Klipsch Lascala / Fh-1 connection. Perhaps some things are taken for granted like the melodies of some country songs. We recognise them as prior art with minor variations. I have always assumed this is a universal sort of thing, but I am learning that it is not the case with speakers, so with that in mind is there prior art for the speaker baffle board? It is after all a guide for the sound waves right?
Last edited:
Thanks Lynn
I hold no grudge towards Ford. They compensated me well and they would have gotten nothing out of my work on waveguides so I could see why they wanted to avoid conflicts of interest on my part.
Pete
I would suspect that the patents (if they existed) would have run out. Klipsch and Peavy are in two very different eras. The folded horn goes way back to the early fifties or before. Peavy didn't even exist at that time. Hartley Peavy is about my age, maybe a little older, but not much.
I would suspect that the patents (if they existed) would have run out. Klipsch and Peavy are in two very different eras. The folded horn goes way back to the early fifties or before. Peavy didn't even exist at that time. Hartley Peavy is about my age, maybe a little older, but not much.
There were a lot of interesting discussions about the history of horns based on the Oblate Spheroidal and/or Ellipic Cylindrical coordinate systems in the "Uniform Directivity" thread too, around post 500 or so:
When I first read Geddes ideas about using the Oblate Spheroidal coordinate system for audio horns, I searched other related disciplines and found many others were using horns with this (Oblate Spheroidal or Elliptic Cylindrical) shape too. Examples can be found in optics, ultrasonics, microwave and sonar.
There is an almost universal attraction to the elliptical coordinate systems, e.g. Oblate Spheroidal and Elliptic Cylinder. Where wavefront propogation is being discussed, devices based on these coordinate systems are often found to have optimal properties.
Where I see this kind of thing, sort of a unified theory, it always causes me to think "we're on to something."
When I first read Geddes ideas about using the Oblate Spheroidal coordinate system for audio horns, I searched other related disciplines and found many others were using horns with this (Oblate Spheroidal or Elliptic Cylindrical) shape too. Examples can be found in optics, ultrasonics, microwave and sonar.
There is an almost universal attraction to the elliptical coordinate systems, e.g. Oblate Spheroidal and Elliptic Cylinder. Where wavefront propogation is being discussed, devices based on these coordinate systems are often found to have optimal properties.
Where I see this kind of thing, sort of a unified theory, it always causes me to think "we're on to something."
And to me "sound is round" its a mini explosion to shape it is to distort it. I find any deviation from spheres sections of spheres cones etc to be so illogical that in my mind only such a horn as,a diffraction type would be a new thought. You can't blame me for being as suprised at this "rights to round" thing as I would be if I found people debating on the patent to roads being flat. In my mind not herding any sort of wave smoothly from one "spherical" sort of transition to another defies common sense. I have heard great sounding horns none really much better than the other if they shared one common denominator. They are sections of round and not totally exponential. I g
You're (again) dramatically understating the issue. Round is not sufficient, "correctly" round is the key. Try making a perfect sphere out of anything (no starting with a sphere) and you'll get a feel for how much variation there can be in "pretty much round" shapes.
I do agree with you that sometimes the importance of the precision is overstated.
Simplicity works. Here then lets truly over simplify. Morph from the driver throat to the horn throat in the most logical manner with nicest possible radius.
I think it's important to remember that the radiating waveshape from all these devices approximates a spherical (or elliptical) section. But they all start as a planar wave. So all of these devices are doing some waveshaping, in that they are morphing a plane wave into a spherical section.
I think what's most important is that it minimize discontinuities along the way.
We talk a lot about Oblate Speroidal horns, but less about other related shapes. For example, look at the Elliptic Cylindrical coordinate system:
A horn profile made from lines tangent to an Elliptic Cylinder has the exact same mathematical expression as one made from lines tangent to an Oblate Spheroid. You can join an OS section at the throat to an EC section at the mouth using the same formula, one that creates the same flare profile. It allows you to merge a round throat with a rectangular mouth.
Again, the radiated wavefront of all these devices approximates a spherical section. But they all start as a planar wave. So all of these devices are doing some waveshaping, in that they are morphing a plane wave into a spherical section.
I think what's most important is that it minimize discontinuities along the way.
We talk a lot about Oblate Speroidal horns, but less about other related shapes. For example, look at the Elliptic Cylindrical coordinate system:
A horn profile made from lines tangent to an Elliptic Cylinder has the exact same mathematical expression as one made from lines tangent to an Oblate Spheroid. You can join an OS section at the throat to an EC section at the mouth using the same formula, one that creates the same flare profile. It allows you to merge a round throat with a rectangular mouth.
Again, the radiated wavefront of all these devices approximates a spherical section. But they all start as a planar wave. So all of these devices are doing some waveshaping, in that they are morphing a plane wave into a spherical section.
Actually you can't do that. The OS wave front is spherical and the EC wave front is cylindrical - they don't match. But, of course, I am just being pedantic because all that really matters is "It goes from here to there - somehow." The details are unimportant.
One could pretty much spin up a clay horn on a potters wheel, back to the Romans. No math required. You sing into one end and listen out on the other side for third order HD. Use a sound meter to get the gain from the human voice direct versus through the horn.
Feinmann would have liked this approach, to then put the math to it.
Sorry, I feel we have all gotten carried away with this horn thing
I was basically paraphrasing you, Earl. You have stated that you believe an OS section could be morphed into a PS or EC section with good results. In fact, you applied for patent on such a device:
Excerpt from the patent:
"The throat of an EC waveguide can be feed by several varieties of sources. First, an actual rectangular source could be used, a phase plug could be made which had a square outlet instead of the usual round one, or a round source could also simply feed the square opening. It is also quite reasonable to assume that a gradual transition from the normal round outlet of a compression driver or speaker to the square section of the EC Waveguide would function without undue degradation of the devices performance, so long as the same cross sectional areas are maintained or grow at a slow rate."
Last edited:
Now this is what amuses me. Transitioning from one plane to another via the shortest and smoothest radius possible is expected of any tradesman for reasons of economy and grace. Deviation from this route would seem superfluous and wasteful. I see this as a given. Arggghhh.
If you consider me "in" audio, you now know one. Very standard texts in physics courses back when I was in college, and the one we used in my math methods in physics two semester sequence.
I spent a couple hours trying to make one of those in Autodesk Design 3D, with little success 🙁
See, here is where a little knowledge is dangerous. You are confusing Elliptic Cylindrical (EC) with Ellipsoidal. Ellipsoidal coordinates are the mother of all coordinates. All other non-paraboloidal coordinates are subsets of the Ellipsoidal - they can be morphed into OS, PS, EC, spherical, cylindrical, everything of importance, but EC cannot be morphed into anything but cylindrical.
I have not said much about Ellipsoidal coordinates because I did not see why I should give away my secrets. But it is clear that I won't be doing anything with them, so what the heck.
Your quote also does not say what you are saying, so please be careful.
Last edited:
- Status
- Not open for further replies.