Much a do about nothing!
This thread is like asking what shade of blue the sky is and getting many different answers. In essence, there is a lot of interpretation and perception mixed in with accepted understanding that differs between folks.
The term waveguide was used in RADAR pretty much from the outset where radio reflections off mountains and valleys has to be differentiated from that enemy plane flying down said valley. This all boiled down to an understanding of how those radio waves bounced around. There were two ways of doing this... 1) have extreme knowledge of how the radar pulse frequency behaves and 2) extreme knowledge of how distortions and noise are created in any echo and how to filter it out.
Why is this relevant? Well, as far as I understand the term waveguide can be applied to anything that guide waves, be they particle waves, radio, microwave, etc. Coaxial cables are considered waveguides. The term waveguide therefore has...
(Key Point 1) Pre-existing meaning in scientific contexts.
On that basis, I would consider it fair and reasonable for somebody who designs an acoustic enclosure of any type to reflect/diffuse or otherwise control acoustic waves to call that mechanism an "acoustic waveguide". I would NOT consider it reasonable to limit this to 'horns', unless they called that a "Horn-waveguide".
Subsequent to the term waveguide being free roaming in science, Earl Geddes has used it in his paper "Acoustic Waveguides" with a particular interpretation based on his pre-existing view of what constituted a 'waveguide'. It so happens, he was investigating horns which controlled acoustic waves but for which the equations are not geared to designing for directivity, so came up with some new formulas that were which he classed as "waveguide" equations to be applied to a particular horn design solving for directivity. Thus, his statement "All waveguides == horns" but "All horns <> waveguides". On the basis of his research, these statements are definitely true. However.....
(Key point 2) These equations are geared towards 'horn' design and not the generality of all acoustic science.
The complexity causing public confusion here is created from Earl's personal interpretation of key point 1 used within a landmark differentiation (empirical and mathematical) with respect to acoustic horn design. This is then made more problematic by the sheer cr*p marketing departments speak which is taking more than a proverbial poetic license with science and English language relativising it all into a meaningless mess to be argued over. This thread being the empirical proof of that.
To solve this scenario I would argue for new unequivocal terms, which are
1) "Standard Horn" a.k.a "horn", which is designed according to traditional horn equations
2) Waveguide-Horn or Horn Waveguide, which is designed according to equations from Earl Geddes' research, but not to simply be called an "acoustic waveguide" and bring it in to conflict with its pre-existing use in science or contradict patented terms by other researchers like Dr Bose who used the term "acoustic waveguide".
This frees up the term "waveguide" to be used as it was in science in the pre-existing case where it is applied to a scenario. In the case of Earl Geddes he applied waveguide equations to 'horn' design, not all of acoustics as a science - so "Acoustic Waveguides" is perhaps not the best thing to call the research paper as it was specific to a particular realm within acoustics. An admission that the research title may not be the most apt does not invalidate or lessen the empirically proven information contained within it, so this should be acceptable.
Thus "waveguide" is a loose term to any "thing" that can guide waves of any type and can be used by anybody. But to be specific about that "thing" requires coupling to whatever that *specific* thing is. In this case *Waveguide* equations specifically applied to *Horn design*.
From this, we can arrive at disambiguation of "waveguide", "horn" (which used singularly defines a "Standard/Traditional Horn" and "waveguide horn". This disambiguation also allows BOSE to use "acoustic waveguide" where their speaker box designs do indeed literally guide acoustic waves.
Now, can we all stop arguing?
This thread is like asking what shade of blue the sky is and getting many different answers. In essence, there is a lot of interpretation and perception mixed in with accepted understanding that differs between folks.
The term waveguide was used in RADAR pretty much from the outset where radio reflections off mountains and valleys has to be differentiated from that enemy plane flying down said valley. This all boiled down to an understanding of how those radio waves bounced around. There were two ways of doing this... 1) have extreme knowledge of how the radar pulse frequency behaves and 2) extreme knowledge of how distortions and noise are created in any echo and how to filter it out.
Why is this relevant? Well, as far as I understand the term waveguide can be applied to anything that guide waves, be they particle waves, radio, microwave, etc. Coaxial cables are considered waveguides. The term waveguide therefore has...
(Key Point 1) Pre-existing meaning in scientific contexts.
On that basis, I would consider it fair and reasonable for somebody who designs an acoustic enclosure of any type to reflect/diffuse or otherwise control acoustic waves to call that mechanism an "acoustic waveguide". I would NOT consider it reasonable to limit this to 'horns', unless they called that a "Horn-waveguide".
Subsequent to the term waveguide being free roaming in science, Earl Geddes has used it in his paper "Acoustic Waveguides" with a particular interpretation based on his pre-existing view of what constituted a 'waveguide'. It so happens, he was investigating horns which controlled acoustic waves but for which the equations are not geared to designing for directivity, so came up with some new formulas that were which he classed as "waveguide" equations to be applied to a particular horn design solving for directivity. Thus, his statement "All waveguides == horns" but "All horns <> waveguides". On the basis of his research, these statements are definitely true. However.....
(Key point 2) These equations are geared towards 'horn' design and not the generality of all acoustic science.
The complexity causing public confusion here is created from Earl's personal interpretation of key point 1 used within a landmark differentiation (empirical and mathematical) with respect to acoustic horn design. This is then made more problematic by the sheer cr*p marketing departments speak which is taking more than a proverbial poetic license with science and English language relativising it all into a meaningless mess to be argued over. This thread being the empirical proof of that.
To solve this scenario I would argue for new unequivocal terms, which are
1) "Standard Horn" a.k.a "horn", which is designed according to traditional horn equations
2) Waveguide-Horn or Horn Waveguide, which is designed according to equations from Earl Geddes' research, but not to simply be called an "acoustic waveguide" and bring it in to conflict with its pre-existing use in science or contradict patented terms by other researchers like Dr Bose who used the term "acoustic waveguide".
This frees up the term "waveguide" to be used as it was in science in the pre-existing case where it is applied to a scenario. In the case of Earl Geddes he applied waveguide equations to 'horn' design, not all of acoustics as a science - so "Acoustic Waveguides" is perhaps not the best thing to call the research paper as it was specific to a particular realm within acoustics. An admission that the research title may not be the most apt does not invalidate or lessen the empirically proven information contained within it, so this should be acceptable.
Thus "waveguide" is a loose term to any "thing" that can guide waves of any type and can be used by anybody. But to be specific about that "thing" requires coupling to whatever that *specific* thing is. In this case *Waveguide* equations specifically applied to *Horn design*.
From this, we can arrive at disambiguation of "waveguide", "horn" (which used singularly defines a "Standard/Traditional Horn" and "waveguide horn". This disambiguation also allows BOSE to use "acoustic waveguide" where their speaker box designs do indeed literally guide acoustic waves.
Now, can we all stop arguing?
Hi,
Sure, I'm all for it. Only one slight quibble.
You forget #3, which is actually represented by most older practical horns:
Empirically designed horn which conforms to neither traditional horn equations or those from Mr. Geddes' or indeed any specific equations...
Ciao T
Sure, I'm all for it. Only one slight quibble.
You forget #3, which is actually represented by most older practical horns:
Empirically designed horn which conforms to neither traditional horn equations or those from Mr. Geddes' or indeed any specific equations...
Ciao T
Infinite gain
An eminately reasonable point of view and recommendation. I wish that I had thought this through better when I published my paper. The term "waveguide" is wide open as you suggest and "acoustic" does not narrow it sufficiently as we can now see. But "Waveguide-horn" is quite precise and exacty on the money.
Thanks for this well thought through post.
An eminately reasonable point of view and recommendation. I wish that I had thought this through better when I published my paper. The term "waveguide" is wide open as you suggest and "acoustic" does not narrow it sufficiently as we can now see. But "Waveguide-horn" is quite precise and exacty on the money.
Thanks for this well thought through post.
Empirical but does not conform to "any specific equations"? An example being?
If it's empirical, maths or some science should be present. If not, I'd say it's a 'cone' or 'funnel' not a 'horn'. However, Earl is happy with my suggestion, so what do you wish for the scenario you speak of? How do we classify it?
Hi,
One is the configuration of the Tannoy Dual Concentrics. The cone and the part inside the polepiece form a spherical horn that conforms to no common horn "equation" (I assume that this implies exponetial, tractix etc.). In fact, may real horns designed in the days before high powered computers became commonplace only loosely follow specific expansions, but often seem to intentionally deviate.
Sure. It has science. As method you shape something, measure the results, change the shape (with mechanical tools) and basically mess with it until you like the result. Of course, you start with some kind of math somewhere, but the final results often vary significantly.
Ahhhmmm. There are horns with conical profile. So it can be a horn and cone.
Due to continuity of expression (if not scientifically correct) I'd call all structures that have a larger exit area then entry area and are connected to acoustic radiators (with or without compression of radiator surface) a horn, regardless how the specific arrangement was arrived upon.
Of course, the same structure could also be referred to as acoustic waveguide with equal right.
A Marketing Department desiring to promote a product with features I would class as "horn" may prefer the term waveguide to avoid possibly incorrect associations with "horn shout" or "horn honk".
On the other hand the Marketing Department desiring a promote a product with features Mr. Geddes would class as "Waveguide (G)" may prefer the term horn as they wish to project continuity with a long heritage of making "Horn" Speaker.
So, my point is we should actually give a pair of fetid dingo kidneys what it is called by marketing departments.
For historical continuity I'd call it a horn, for that what in general parlance it is.
Ciao T
One is the configuration of the Tannoy Dual Concentrics. The cone and the part inside the polepiece form a spherical horn that conforms to no common horn "equation" (I assume that this implies exponetial, tractix etc.). In fact, may real horns designed in the days before high powered computers became commonplace only loosely follow specific expansions, but often seem to intentionally deviate.
Sure. It has science. As method you shape something, measure the results, change the shape (with mechanical tools) and basically mess with it until you like the result. Of course, you start with some kind of math somewhere, but the final results often vary significantly.
Ahhhmmm. There are horns with conical profile. So it can be a horn and cone.
Due to continuity of expression (if not scientifically correct) I'd call all structures that have a larger exit area then entry area and are connected to acoustic radiators (with or without compression of radiator surface) a horn, regardless how the specific arrangement was arrived upon.
Of course, the same structure could also be referred to as acoustic waveguide with equal right.
A Marketing Department desiring to promote a product with features I would class as "horn" may prefer the term waveguide to avoid possibly incorrect associations with "horn shout" or "horn honk".
On the other hand the Marketing Department desiring a promote a product with features Mr. Geddes would class as "Waveguide (G)" may prefer the term horn as they wish to project continuity with a long heritage of making "Horn" Speaker.
So, my point is we should actually give a pair of fetid dingo kidneys what it is called by marketing departments.
For historical continuity I'd call it a horn, for that what in general parlance it is.
Ciao T
There is no contour for which Websters Equation cannot be applied, within its quite limited assumptions of course, even if the solution is not closed form and hence not really known. In that same vein there is no contour that cannot be solved numerically.
The waveguide-horn equations are quite precise and can only be applied to very few contours. This is quite a different situation. I have posted before the extremely interesting results that one obtains when the OS contour is used in Websters equation, showing, of course that a waveguide is a horn, but not all horns are waveguides.
And they may wish to capitalize on the praise bestowed on my approach by calling the same old stuff a "Waveguide".
That is what I was trying to argue for. And I was proposing that if something was just a random, or horn-like shape from informal listening and approval that maybe we should not call those horns - chiefly because we differentiated yours as waveguide-horns (due to new science helping design them) from traditional horns (empirically designed to contemporary horn equations) and by extension those which have no empirical basis other than the definition by shape should be recognised by that shape, ergo 'cone' or 'funnel' etc.
I think Thorsten isn't buying any of this as he wants to call all these different acoustic engineering apertures 'horns' and put the rest down to semantics (as he posted earlier just before you intervened to correct him). However, this leaves people like the thread initiator validly asking for somebody to tell them the difference between 'horn' and 'waveguide'. Yet, it seems that because vague reference use persists, that nobody can succinctly answer the question with any universal solidarity in the academic realm.
Thorsten also appears to wish to allow marketing companies to call things whatever they will. This is of course fine in a free society (although it is fuel for disinformation), but the informed public, or educated person, academic student etcetera needs clear definitions by which to 'discern' and thereby 'know' which areas of science apply to a design and not be deceived by marketing technobabble.
Convincing somebody a product is better is one thing, lying or deceiving to do so is something else. The consumer audiophile market is full of pseudo-scientific claims helping spread unsound science and leading many a DIYer up the proverbial garden path. How is this good for furthering audio science?
I would rather not let marketing companies intrude on the empirical, scientific side and otherwise 'dumb down' those DIYers trying to learn. If we aren't censoring the marketing ads, then we need the ability to have correct and clear definitions available to people when they want to look at something from a scientific/academic viewpoint.
It seems many are bamboozled by marketing pseudoscience and vague pseudo-science references. If the DIY disciple is to learn, there MUST be a means to 'discernment' that is empirical and informed. To do this, we in the DIY community or the research community for the actual science, must make a means of discernment apparent to all and not just use top-level classifications such as 'horn' or 'waveguide' to be interchangeably used to cover all and sundry.
I am sure people would rather be called 'people', than the higher level 'mammal', 'animal' or 'lifeform', but it seems obvious to respect that. However, in the science and marketing domains, such distinctions are increasingly blurred causing much misrepresentation and relaying of spurious so called facts, which self educated persons then disseminate as 'truth' when they are misrepresentations.
In the end, if you don't say what you mean, then you don't mean what you say! Correctness of fact in science and the educated DIY hifi community starts or ends with us taking such things seriously.
To me, a shape that is used sonically by happenstance is just that, be it a cone, cube, sphere etc. One that is by some reproducible formula of design geared to producing that shape has some specific classification. In your case, all those equations that can be applied to any acoustic 'horn' - if those equations were applied in its creation, then it is indeed an acoustic 'horn'. For all those where they used your research equations to examine the 'horns' directivity, they are indeed 'waveguide-horns'. But just "waveguide" does not suffice.
I wouldn't accept it as 'reasonable' for a marketing company to call a waveguide-horn just a "waveguide" or just a "horn" as to not tell the public *exactly* what it is. To do so is a little misleading. You'd be a bit upset if a company advertised a car as having a sporty 500bhp and then when you bought it, found out it was actually the electrical equivalent, weighed too much and performed like a certain Japanese hybrid vehicle - you'd feel misled.
However, this happens everyday and results in those taking a foray in to the science having a hard time because scientific solidarity doesn't exist. Categoric classification is ruling over specific classification. Vagueness is in vogue. Using English correctly is on the wane (mine's not the best either).
Your scientific results may be accepted, but people don't call a 'spade a spade' as Thorsten said he liked to earlier. It will be referred to later in vague terms and result in spurious and nefarious claims and pseudo-science becoming more prolific than real science and the real scientists having no solidarity to prevent/cure the situation. Thus they harmed the science they themselves tried to take forward. A 'waveguide horn' is a 'waveguide horn' not just a 'horn'. It is "a-type-of 'horn'" (category classification) but it is not (by specific classification) just a 'horn'.
Hi,
Forgive me, but that is what is wrong with todays science.
So, if I arrive at the EXACT same result twice, one time by extended calculation, mathematical exercises and the like in the virtual realm of paper and academia, the second by trial and error empirical excercise in the physical realm of actual research (which I hasten to add Mr. Geddes has been much engaged in) I cannot use the same world to describe the results?
So a round wheel designed in Cad-Cam is not the same as a round wheel made by cart maker by hand and without equations and computers? Please do illuminate me what we call the second?
Ciao T
Forgive me, but that is what is wrong with todays science.
So, if I arrive at the EXACT same result twice, one time by extended calculation, mathematical exercises and the like in the virtual realm of paper and academia, the second by trial and error empirical excercise in the physical realm of actual research (which I hasten to add Mr. Geddes has been much engaged in) I cannot use the same world to describe the results?
So a round wheel designed in Cad-Cam is not the same as a round wheel made by cart maker by hand and without equations and computers? Please do illuminate me what we call the second?
Ciao T
No Thorsten, I used the word 'random' and what you describe is not random. Trial and error is informed decision making by isolating a variable and playing with it or trying to ascertain what the change influences.
Just edited to answer your second part...
My point is this:
The thread starter asked what is the difference between a waveguide and a horn.
The key word is 'difference'. Another way to ask, would be, "what is the differentiating factor that makes one thing scientifically recognised with one name, and a similar thing with another name"?
To do this, we need to scientifically classify what makes an "acoustic horn" and "acoustic horn". If it's a random shape used in acoustics, is that an "acoustic horn" or simply a shape with acoustic properties?
Then we need to say what is a "waveguide". If a "waveguide" can be applied to the category of "horns", what is the resultant output - in this case a "waveguide horn" with unique properties of directivity, which NOT ALL "horns" share. Thus we would be differentiating or discerning and informing the person asking the question.
If we do not differentiate and just say, it's all semantics, they are all just "horns", we inform the questioner of no helpful information.
It is not whether something is done by computer/equation that determines what we call it. It is the purpose for which it is designed. A CAD-CAM wheel is designed to be a wheel just as a handmade one is. However, if somebody happens to create a shape that randomly acts like a horn, it does so by chance and not design. What we call it is what the designer intended it to be, rather than 'what' we can ascribe to it. (Edit: I think it's probably a combination of both and not just the intention or what others think).
A tree trunk was always a tree trunk until somebody used it to move stones to Stonehenge. At that point, the intention or design purpose changed and it became a wheel.
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Hi,
Yup. Agreed.
However, all engineering is like that. Trial and error in some domain, to get results in reality.
Ciao T
Yup. Agreed.
However, all engineering is like that. Trial and error in some domain, to get results in reality.
Ciao T
Still not precise enough. All horns have directivity. A "waveguide" by Earl's definition exhibits a specific class of directivity, namely "constant" directivity (though the definition of that term is itself imprecise), derivative of a specific approach, his approach, and that only, which he seeks to distinguish.
How many times have we seen him assert, "I coined the term and was the first to use it, so I get to say what it means?"
He didn't, and he wasn't, rather, he merely appropriated "waveguide" to his own specific use, and in all conceit, frankly, rails against any and all others. Conceptually, we understand the difference, but his claim to "ownership" of this terminology falls well short of its mark....
Again, it's simple.. go back and read my prior post.
Earl's use of the words IS MARKETING. ..plain and simple (cr@p or otherwise).
His use was almost certainly intended for an academic market (initially).. but more recently it has become commercial. ..And there is nothing wrong with either. In the academic sense he defines what he regards as a Waveguide.. he could have just as easily called it "dog", so long as he defines what "dog" is. In the commercial sense he can pretty much say whatever he wants to - as Thorsten put's it: it's "FNORD"-speak.
What is obviously incorrect however is that he holds any legitimate claim to "waveguide" as far as common use is concerned (..or it's "simple" meaning). Hell, Elias even provided a *published academic* use of the word prior to what he claims. (..and I suppose as far as academics are concerned we could go back to Lord Rayleigh..)
WAVEGUIDE is an obvious conjunction with an obvious meaning: to guide waves (..in this context sound waves, or even more appropriately - audible sound waves).
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still not precise enough. All horns have directivity. A "waveguide" by earl's definition exhibits a specific class of directivity, namely "constant" directivity (though the definition of that term is itself imprecise), derivative of a specific approach, his approach, and that only, which he seeks to distinguish.
How many times have we seen him assert, "i coined the term and was the first to use it, so i get to say what it means?"
he didn't, and he wasn't, rather, he merely appropriated "waveguide" to his own specific use, and in all conceit, frankly, rails against any and all others. Conceptually, we understand the difference, but his claim to "ownership" of this terminology falls well short of its mark....
exactly..
..and it's unfortunate that his use causes misunderstanding rather than increasing understanding.
Agree with the above. Specificness (if that's a word), or precision/conciseness is important to coining a term or a category. We must understand the differentiating factors.
My concern is that such things are allowed to propagate and what it means for those trying to learn in a world where such terms are tossed around together with pseudo-scientific knowledge and when somebody asks, "what's the difference...." nobody seems to be able to give an authoritative answer.
My concern is that such things are allowed to propagate and what it means for those trying to learn in a world where such terms are tossed around together with pseudo-scientific knowledge and when somebody asks, "what's the difference...." nobody seems to be able to give an authoritative answer.
I'll restate it: (..maybe that will make it more authoritative..
)*Wave* *Guide*
Guiding waves, or directing waves. Limiting dispersion by physical means.
Of course limiting dispersion *can* also include gain (..assuming the guide doesn't absorb the wave). In fact it *usually* includes gain.
If the primary reason to guide an acoustic wave is to increase gain then it's a Horn. (..originally derived by bearing a similarity to animal "horns".)
If the primary reason to guide an acoustic wave is to limit dispersion ("shape" it), then it's a Waveguide.
Functionally all Horns are Waveguides, but not all Waveguides are Horns. You can have a Waveguide that absorbs and does not increase gain, but all Horns rely on "compressing" the dispersion pattern to increase gain in a particular direction.
I don't think you'll find anything under common definitions (in the context we are discussing) that would materially disagree with the above either.
The one area that I think has some "wiggle" to is is limiting dispersion with strictly *physical* means - though that is what is most *common*.
I'll restate it: (..maybe that will make it more authoritative..
*Wave* *Guide*
Guiding waves, or directing waves. Limiting dispersion by physical means.
Of course limiting dispersion *can* also include gain (..assuming the guide doesn't absorb the wave). In fact it *usually* includes gain.
If the primary reason to guide an acoustic wave is to increase gain then it's a Horn. (..originally derived by bearing a similarity to animal "horns".)
If the primary reason to guide an acoustic wave is to limit dispersion ("shape" it), then it's a Waveguide.
Functionally all Horns are Waveguides, but not all Waveguides are Horns. You can have a Waveguide that absorbs and does not increase gain, but all Horns rely on "compressing" the dispersion pattern to increase gain in a particular direction.
I don't think you'll find anything under common definitions (in the context we are discussing) that would materially disagree with the above either.
The one area that I think has some "wiggle" to is is limiting dispersion with strictly *physical* means - though that is what is most *common*.
Yes, but its the wiggle-room and vagueness that causes the issues - particularly when somebody asks for a de facto differentiation and the result is lots of 'experts' in audio start arguing. As I see it, whatever the marketing people or somebody with a marketing angle (even if a scientist) wants to come up with, research should undergo an acceptable peer-reviewed stance on the thing being named/classified so that there is a clear-cut definition that somebody can go to that will educate and undo the pseudo-science being tossed about and absorbed as fact by some people. (They shouldn't be able to try and monopolize a pre-existing scientific term with greater meaning). It seems to me the research findings can be supported but nobody is concerned what happens with the name of something being coined and if it's actually already taken by definition. Trademarks excluded of course.
FWIW ScottG, your definition is good and probably the clearest here, but you're just an anonymous internet avatar to me, so I cannot lend you the award of "authoritative" much as I'd like to.
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