With a little difference considering the wave length of the light VS the diameter of the fiber ?
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The ratio is quite different of course. My fiber analogy was more a single mode/multi mode/path length thing.
But actual measurement of the effect in a horn is a tough nut.
I can see how listening tests would be the primary test method.
I must admit confusion as to the foam thing explanation, as I'd expect a "percentage of whole" being absorbed, not 10 out of 20 vs 10 out of 100.
Perhaps Mr. G can elaborate on why?
jn
About listening tests, comparing with spherical waves calculated horns.. hum... how to say ?
I have been and will be rather sketchy on all of this here because its not the appropriate forum for the discussion of waveguides. This has been discussed at some length over in loudspeakers.
You are quite correct about the modes in fiber optic cables. Its very analogous, except that in waveguides the walls are not parallel and hence the modes are not only much more complex, but they change as they propagate. Fiber modes don't do that.
You are also quite correct about the difficulty in measuring the HOM. This is why when I hear that someone has done it, I am very sceptical. It was done, once, by a guy at Aachen using a microflown and a scanning device. He measured their presence but nothing else. His setup would be impossible in a setting like I have.
By "proof" I meant that my devices have been in the marketplace for more than a decade and they work in practice just like the theory says that they should - the main parts, not the HOM. The HOM are pretty hypothetical at this point - except that their existance has been proven in theory and in measurements, but their audiblity is a work in progress. Given that all the testable parts of Waveguide Theory have proven to be correct, I have every reason to believe that the HOM claims will also be shown to be correct when such measurements are feasible.
Regarding the foam, I am not sure if it is a percentage or a flat reduction. In either case my point is that with a device with high HOM the foam is not very effective, but with a low HOM it is. Although I have heard people say that it works well even on bad devices - could be. Its the claim that I use foam because the HOMs are large that is completely bogus.
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And what about simulations ? (fluid dynamic)
(btw: JMLC 's community has provided very useful sim tools, they improve them continuously, they correlate more and more with measurement and they show with evidences the diffractions problems induced by any lack of progressivity near the throat.)
On my little experience, dumping horn with different foams, glass wool etc.., i had good results with bad horns or waveguides on the response curve, while terrific deterioration with good horns. ( loss of efficiency, added distance the sound source, and loss of intelligibility or definition not related with the obvious loss of trebles ).
May-be Mr Gedlee can explain that ?
About two hours after that post someone walked into my office with a package from the CEO of Stanford Instruments that he had lost for over 5yr. It was about all of my stuff he uses. Scarey.
Damping adds distortions. It is non-linear. You trade-off frequency response for distortions. No free cheese for mice, except in the mousetrap!
Let me google that for you
Let me google that for you
And, synchronicity over here! I don't know, this forum is getting too spooky for me ...
Frank
I agree, I was going to play around with exciting the waveguide with an impulsive wavefront (at the throat) just to see what I can see. Right now the HOM theory makes intuitive sense to me I just need to put the kits together and listen, I HATE traditional horn speakers in most incarnations so we shall see.
OTOH analogies that cross different diciplines in physics sometimes fool you.
And, synchronicity over here! I don't know, this forum is getting too spooky for me ...
Frank
I'm not exaggerating, this was a real double take moment. My retired ex-boss poked his head in my door and said after moving all his stuff to a new house this turned up.
For example, when optical/EM phenomena propagate without an elastic medium, versus acoustical phenomena that rely upon one.
They are simulations. They can't show what were left out of equations. But a smoke can reveal, like it does when they test aerodynamics.
I will be serious for a change and subjective as well.
I had the chance, few years ago to listen to the 12" enclosure from Gedlee.
They are very good speakers, the best finished enclosures of this size i've heard on the market . They bring all that i like from horns (dynamic and efficiency), and present no coloration at all. Just, may-be, not those deep and fast basses i like, a little excess of level around 2-4KHz (very little), and something a little too much damped in the hight (probably effect of the foam).
They have a good localization and restitution of distances .
Most off all, i don't liked all previous waveguide i've heard before. Those don't suffer at all of the disagreeable (like distorted) characteristic of them.
A complete success to bring to people, at reasonable price, all the best of high efficiency and dynamic.
How to be more laudatory ? I would not say that of all of the studio monitors i know.
At this time, i don't knew at all about Mr Gedlee and was pretty admirer.
After that, i've read many comment from him and visited his site. Well, i believe the communication's quality is way under the quality of those enclosures. And those assumptions about HOMs put me in a very suspicious position. (i don't say they don't exists)
In fact, it would be unfair to compare with my enclosures, as they don't play in the same yard , not the same price neither the same power handling and efficiency. (3db)
But i can assure you that my enclosure present no more colorations (and may-be less) or "distorted feeling" despite no care had be taken about those mysterious HOMs, reason of my joke about.
On the contrary, they are more "free" and "easy", gives more "air", localization is the same order of quality, with a little more space between instruments. As the Gedlee's, i use to listen to them with an angle from the axis (20° on mine).
Basses, nothing to compare, of course.
My conclusion ? If i had to buy a little system, i would buy Gedlee's enclosure, despite this poor consideration for the work of other very talented people, searching for the same results with as much success and a different approach. Like my friend François Delamare or JMLC witch has a very scientific and modest approach, and justify all his assumptions with numbers and references. And it is not because they are French
I can understand why business need to keep some 'secrets' or unjustified argues, but this does not help to keep a perfect scientific posture.
I had the chance, few years ago to listen to the 12" enclosure from Gedlee.
They are very good speakers, the best finished enclosures of this size i've heard on the market . They bring all that i like from horns (dynamic and efficiency), and present no coloration at all. Just, may-be, not those deep and fast basses i like, a little excess of level around 2-4KHz (very little), and something a little too much damped in the hight (probably effect of the foam).
They have a good localization and restitution of distances .
Most off all, i don't liked all previous waveguide i've heard before. Those don't suffer at all of the disagreeable (like distorted) characteristic of them.
A complete success to bring to people, at reasonable price, all the best of high efficiency and dynamic.
How to be more laudatory ? I would not say that of all of the studio monitors i know.
At this time, i don't knew at all about Mr Gedlee and was pretty admirer.
After that, i've read many comment from him and visited his site. Well, i believe the communication's quality is way under the quality of those enclosures. And those assumptions about HOMs put me in a very suspicious position. (i don't say they don't exists)
In fact, it would be unfair to compare with my enclosures, as they don't play in the same yard , not the same price neither the same power handling and efficiency. (3db)
But i can assure you that my enclosure present no more colorations (and may-be less) or "distorted feeling" despite no care had be taken about those mysterious HOMs, reason of my joke about.
On the contrary, they are more "free" and "easy", gives more "air", localization is the same order of quality, with a little more space between instruments. As the Gedlee's, i use to listen to them with an angle from the axis (20° on mine).
Basses, nothing to compare, of course.
My conclusion ? If i had to buy a little system, i would buy Gedlee's enclosure, despite this poor consideration for the work of other very talented people, searching for the same results with as much success and a different approach. Like my friend François Delamare or JMLC witch has a very scientific and modest approach, and justify all his assumptions with numbers and references. And it is not because they are French
I can understand why business need to keep some 'secrets' or unjustified argues, but this does not help to keep a perfect scientific posture.
Some candid questions about those HOMs.
- About comparing with optics, are horns something else than a lens ?
Any HOM in a lens ? Something else than chromatic aberration ?
- Is the front of pressure supposed to be pseudo spherical (depending of the driver) by JMLC, reflect itself on the walls of the horn ?
Or is-it more like a wave on the water with well known diffraction phenomenas if it hits obstacles ?
- What about the different waves lengths Vs the throat diameter ?
Lets suppose that the sound is like some kind of photons bouncing on the walls of the horn when out of axis. (fiber comparison)
Any chance those photons to finish their course in the axis with a exponential horn ?
So some sound arrive with some delay in some axes ? We can see the distortion induced by the delay and the change of level at this frequency when added with strait signal: No accident in the response curve we can measure ?
Problems with the non linearity of air with crossed waves ? Again no way to measure distortion ?
There are simulation tools witch shows the pressure repartition at different frequencies VS angle. We can see effects of diffractions in space.
Why those mysterious HOMs are not measurable, i mean at least their effects ?
Did i missed something ?
- About comparing with optics, are horns something else than a lens ?
Any HOM in a lens ? Something else than chromatic aberration ?
- Is the front of pressure supposed to be pseudo spherical (depending of the driver) by JMLC, reflect itself on the walls of the horn ?
Or is-it more like a wave on the water with well known diffraction phenomenas if it hits obstacles ?
- What about the different waves lengths Vs the throat diameter ?
Lets suppose that the sound is like some kind of photons bouncing on the walls of the horn when out of axis. (fiber comparison)
Any chance those photons to finish their course in the axis with a exponential horn ?
So some sound arrive with some delay in some axes ? We can see the distortion induced by the delay and the change of level at this frequency when added with strait signal: No accident in the response curve we can measure ?
Problems with the non linearity of air with crossed waves ? Again no way to measure distortion ?
There are simulation tools witch shows the pressure repartition at different frequencies VS angle. We can see effects of diffractions in space.
Why those mysterious HOMs are not measurable, i mean at least their effects ?
Did i missed something ?
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