gedlee said:
I appreciate a "please" when people ask me to give them things
Simply because chapter 9.2 in the book "Theoretical Acoustics" by Morse and Ingard (1986) is titled "Higher Modes in Ducts", and as far as I understand the text, it discusses higher order modes. Not HOMs in horns, that is true, but still HOMs. Please correct me if I'm wrong.
Earlier you wrote: "Now, if you believe that there were others who discussed this problem with something more than a simple hypothetical or hueristic treatment then I'd love to have the reference as I know of no such writings." You did not mention that the reference should contain a general treatment for all kinds of horns, only that it should be more than a hypothetical treatment, and I believe that is what I have refered to.
I did not dispute that, I was just pointing out that Hoersch also did some work on this topic.
Regards,
Bjørn
gedlee said:
Yes. You are correct that it wasn't commonly used in building construction for many years after its invention, and Wright's use at Falling Water of reinforced concrete in dramatic cantilevers was pushing well beyond the more common and better understood usage.
For the record, I'm not a professional architect, having been diverted into software engineering long ago.
Hello,
Just to mention that reinforced concrete was invented and patented in 1870 by the French engineer Joseph Monier.
http://fr.wikipedia.org/wiki/Joseph_Monier
It common use began in Europe circa 1890.
Best regards from Paris, France
Jean-Michel Le Cléac'h
Just to mention that reinforced concrete was invented and patented in 1870 by the French engineer Joseph Monier.
http://fr.wikipedia.org/wiki/Joseph_Monier
It common use began in Europe circa 1890.
Best regards from Paris, France
Jean-Michel Le Cléac'h
gedlee said:
Hello,
Wilkinson invented a use of embedded strips of steel inside cement in the goal of fire prevention for what I guess. I don't know if this can be called "reinforced concrete"... may be
http://en.wikipedia.org/wiki/Reinforced_concrete
But before Wilkinson there was also the French Joseph-Louis Lambot :
http://en.wikipedia.org/wiki/Joseph-Louis_Lambot
But still the official creation is attributed to Monier... ... at least in France.
Best regards from Paris, France.
Jean-Michel Le Cléac'h
Wilkinson invented a use of embedded strips of steel inside cement in the goal of fire prevention for what I guess. I don't know if this can be called "reinforced concrete"... may be
http://en.wikipedia.org/wiki/Reinforced_concrete
But before Wilkinson there was also the French Joseph-Louis Lambot :
http://en.wikipedia.org/wiki/Joseph-Louis_Lambot
But still the official creation is attributed to Monier... ... at least in France.
Best regards from Paris, France.
Jean-Michel Le Cléac'h
MEH said:
Much more daring. The Pantheon is a compression structure. It plays to concrete's strength and doesn't require reinforcement to carry a tensile load.
For a concise history of reinforced concrete as a building material, see Historic Concrete: Background to Appraisal, chapters 4 and 5.
For a concise history of reinforced concrete as a building material, see Historic Concrete: Background to Appraisal, chapters 4 and 5.
Hello,
http://www.musique-concrete.com/
http://www.musique-concrete.com/Emat.htm
though those are not waveguides but horns, sorry...
Best regards from Paris, France
Jean-Michel Le Cléac'h
http://www.musique-concrete.com/
http://www.musique-concrete.com/Emat.htm
though those are not waveguides but horns, sorry...
Best regards from Paris, France
Jean-Michel Le Cléac'h
soongsc said:
Jmmlc said:
Jean-Michel
Interesting page - thanks.
On this point I think that we can agree. I don't like weak flimsy horn/waveguides either. Simple fiberglass never works for me nor injection molding (wall thickness limitations). I think that you would be very impressed with the waveguides that I am doing now cast in micro-ballon filled polyurethane. This material is incredible as it is very hard and rigid and well damped, but actually quite light (the micro-ballons wheigh almost less than air). This is the best material that I have ever found for making waveguides (or horns).
Kolbrek said:
I appreciate a "please" when people ask me to give them things
PLEASE!
Kolbrek said:
The subject of HOMs in ducts is well known, I have agreed to this before, but its not a small extension of the theory to extend these concepts to waveguides. Hence I don't consider the straight duct HOMs to be precursor to those on a flaring duct. You may disagree on this point, but you do have to agree that the math is quite a bit more ellaborate for the waveguide
Hello Earl,
I agree with you about the required behavior for the material to build horns and waveguides.
Your's is surely interesting for internal damping (I recommanded many times to Marco Henry to use micro balloons in his material).
Thickness of the wall along the axis is very important too to damp vibration of the whole structure. Most often molded horns possess a constant thicness of their walls and while this is this for sure an easy solution it is surely a bad thing when it comes to virbation damping.
here is a FEM simulation of how strains a flimsy theorical Le Cléac'h horn:
http://www.musique-concrete.com/matP/mat15.jpg
from such studies we can obtain information on the right places along the horn's wall where we have to increase the thickness.
Best regards from Paris, France
Jean-Michel Le Cléac'h
I agree with you about the required behavior for the material to build horns and waveguides.
Your's is surely interesting for internal damping (I recommanded many times to Marco Henry to use micro balloons in his material).
Thickness of the wall along the axis is very important too to damp vibration of the whole structure. Most often molded horns possess a constant thicness of their walls and while this is this for sure an easy solution it is surely a bad thing when it comes to virbation damping.
here is a FEM simulation of how strains a flimsy theorical Le Cléac'h horn:
http://www.musique-concrete.com/matP/mat15.jpg
from such studies we can obtain information on the right places along the horn's wall where we have to increase the thickness.
Best regards from Paris, France
Jean-Michel Le Cléac'h
gedlee said:
gedlee said:
You got mail
I hope I sent it to the right address, I used the same that we have used for correspondence before. I agree with you on this. It was just that since you have written much about HOMs and your work on the topic in this forum, one might be led to believe that you were, or claimed to be, the first one to cover the topic in general. I'm certain that this was not your intention.
(I can't remember to have read the post(s) where you mention HOMs in ducts, but I haven't read every single post you have written on this forum either
).It will be interesting to hear your thoughts on the Hoersch paper.
Best regards,
Bjørn
Kolbrek said:
You got mail
It will be interesting to hear your thoughts on the Hoersch paper.
Best regards,
Bjørn
Yes, you are quite correct in that he does describe in detail how the waves have a non-radial component and have differing trace velocities - thus are dispersive. But he really doesn't actually do the waveguide problem since there is no source.
His mathematics is very hard to follow and I think that these days the problem is much easier to solve numerically as shown in my book. I have never seen this paper referenced before, it is quite obscure. The standing wave patterns are very interesting in how the wavelengths change with radial value. As you said his mouth boundary condition is incorrect and his throat is assumed to be of zero size - both of which are unrealistic and correcting them makes the problem much more complex. You can see this complete solution in my book and the appendix which I posted on my web site.
graaf said:
great! of course I mean it is great to read the answer from You Dr Geddes!
so only one part of my question remains unanswered but at the same time it is the most interesting:
please answer please
best regards,
graaf
The waveguide would not have an axisymmetric coverage pattern. Its generally desirable to have a smaller coverage vertically than horizontally. But at the crossover the woofer is going to be axi-symmetric, so its a tradeoff. One that I have choosen not to make.