Hello Helmuth,
You asked:
My answer will differ somewhat of David's one (sorry David).
You can simulate a 1" or a 2" horn without knowing the Thiele and Small parameters, introducing Eg = 0 (in place of the normal value Eg = 2,83).
Doing this the driver will be considered as a "constant velocity source". This feature is very interesting when designing new horns without knowing the Thiele and Small parameters. For sure the results will be better than with a real driver, specially in the HF (because moving mass = 0)
Best regards from Paris, France
Jean-Michel Le Cléac'h
You asked:
My answer will differ somewhat of David's one (sorry David).
You can simulate a 1" or a 2" horn without knowing the Thiele and Small parameters, introducing Eg = 0 (in place of the normal value Eg = 2,83).
Doing this the driver will be considered as a "constant velocity source". This feature is very interesting when designing new horns without knowing the Thiele and Small parameters. For sure the results will be better than with a real driver, specially in the HF (because moving mass = 0)
Best regards from Paris, France
Jean-Michel Le Cléac'h
Hi Jean-Michel,
Many thanks. I had completely forgotten about the driver diaphragm constant velocity option, included in Hornresp at your suggestion
.Kind regards,
David
Hello David and Jean-Michel,
In the JMLC_horn_v2 spreadsheet I get the impression that the sides of a square horn(4petals) are radius*2 of the round(at the same length in the horn).
Voight recommends the same in his patent.
Ie this is a area difference of a factor ca 1,27 relative round.
Seems like the area is the same whatever shape in Hornresp.
Have I gotten it all wrong? Anyway, pros and cons of the two ways of doing it?
In the JMLC_horn_v2 spreadsheet I get the impression that the sides of a square horn(4petals) are radius*2 of the round(at the same length in the horn).
Voight recommends the same in his patent.
Ie this is a area difference of a factor ca 1,27 relative round.
Seems like the area is the same whatever shape in Hornresp.
Have I gotten it all wrong? Anyway, pros and cons of the two ways of doing it?
Hi Lars,
The approach taken in Hornresp for square / rectangular horns is very simple. Assuming the plane cross-sectional area at axial length X is given by AREA, then Width at X = AREA / (Height at X).
It is quite some time since I last looked at Jean-Michel's spreadsheet, but I seem to recall that it takes into account the area of the curved wavefront when determining the required rectangular cross-section at a given axial length. Jean-Michel's approach would be more correct theoretically. I'm not sure how much of practical difference it makes though. He may care to comment further.
Kind regards,
David
Hello Revintage,
This question is a bit off topic here. Anyway I hope David will not feel offended if I reply here.
If you use a number of petals of 4, both the mouth and the throat are square. A square possess an area 1.2372 times larger than the inscribed circle.
As square drivers are pretty rare, if you want to use a circular driver you'll have to use an adpatator from round to circle between the driver and the horn.
I once wrote an Excel spreadsheet to calulate adptatators of the desired frequency from circle to retcangular. Infortunately it is in French, see here attached the excel spreadsheet in txt format).
Best regards from Paris, France
Jean-Michel Le Cléac'h
This question is a bit off topic here. Anyway I hope David will not feel offended if I reply here.
If you use a number of petals of 4, both the mouth and the throat are square. A square possess an area 1.2372 times larger than the inscribed circle.
As square drivers are pretty rare, if you want to use a circular driver you'll have to use an adpatator from round to circle between the driver and the horn.
I once wrote an Excel spreadsheet to calulate adptatators of the desired frequency from circle to retcangular. Infortunately it is in French, see here attached the excel spreadsheet in txt format).
Best regards from Paris, France
Jean-Michel Le Cléac'h
Hello David and Jean-Michel,
I am aware that the 4 petal horn is square from start to end. I am sure you menat 1,2734? Still the thing making me wonder is that the "4-petal" from the spreadsheet does not equal a square LeCleach in Hornresp.
The question came up as I thought of using a cone driver to a midbasshorn that should be square all the way.
Just for fun this is from Voigts patent 1927:
"In the case of a square horn, the tangent to the corners is longer than that to the middle of the sides and a compromise is unavoidable. I prefer to make the section correspond to the tractrix. The shortest tangent is then correct, but the area is 4/Pi=1,27 times that of the corresponding tractrix.
If the area is made equal to the corresponding tractrix, the tangent at the sides will be short, a defect which is partly compensated for by the excess length of the tangent to the corners."
About the OT I too did a round to square spreadsheet a few years ago intended for tractrix. Must check to see if mine where made good enough...
I am aware that the 4 petal horn is square from start to end. I am sure you menat 1,2734? Still the thing making me wonder is that the "4-petal" from the spreadsheet does not equal a square LeCleach in Hornresp.
The question came up as I thought of using a cone driver to a midbasshorn that should be square all the way.
Just for fun this is from Voigts patent 1927:
"In the case of a square horn, the tangent to the corners is longer than that to the middle of the sides and a compromise is unavoidable. I prefer to make the section correspond to the tractrix. The shortest tangent is then correct, but the area is 4/Pi=1,27 times that of the corresponding tractrix.
If the area is made equal to the corresponding tractrix, the tangent at the sides will be short, a defect which is partly compensated for by the excess length of the tangent to the corners."
About the OT I too did a round to square spreadsheet a few years ago intended for tractrix. Must check to see if mine where made good enough...
Hi Lars,
I think Jean-Michel actually meant to say 1,2732 (4 / Pi accurate to 4 decimal places), but managed to transpose the 7 and 3
.Kind regards,
David
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Hello revintage
Yes I inverted the 7 and the 3 in the number (my vision is very bad...).
It is easy to understand that value:
........... the area of a square having a length of its edge = 1 is 1.
............the area of the circle included in that square is pi/4
The ratio between the area of the square and the area of the circle is thus:
........................... 4/pi = 1.27323945
(you missed the second 2 )
In the case you use a cone driver being larger than the square throat, there is no problem to use a square throat as long as it is all incuded (in projection) in the active part of the membrane. Doing this you provide a compression chamber to the loudspeaker.
Best regards from Paris, France
Jean-Michel Le Cléac'h
Yes I inverted the 7 and the 3 in the number (my vision is very bad...).
It is easy to understand that value:
........... the area of a square having a length of its edge = 1 is 1.
............the area of the circle included in that square is pi/4
The ratio between the area of the square and the area of the circle is thus:
........................... 4/pi = 1.27323945
(you missed the second 2 )
In the case you use a cone driver being larger than the square throat, there is no problem to use a square throat as long as it is all incuded (in projection) in the active part of the membrane. Doing this you provide a compression chamber to the loudspeaker.
Best regards from Paris, France
Jean-Michel Le Cléac'h
Hello Revintage,
You wrote,
That's a difficult problem.
Only modes 00, 0i, j0 exist with round horns but in horns having square or rectangular mouth other HOMs exist.
As an example see how the Altec 311-60 horn radiates (see attached graph from Altec data sheet).
What seems to happens is that the corners inside the horns have lower pressure than the near axial zones.
For a square horn eventually we could say that from the radiation point of view the horn emit nearly like if a round horn was inserted inside the square horn (that's a bad image but I hope you see what I mean)
Best regards from Paris, France
Jean-Michel Le Cléac'h
You wrote,
That's a difficult problem.
Only modes 00, 0i, j0 exist with round horns but in horns having square or rectangular mouth other HOMs exist.
As an example see how the Altec 311-60 horn radiates (see attached graph from Altec data sheet).
What seems to happens is that the corners inside the horns have lower pressure than the near axial zones.
For a square horn eventually we could say that from the radiation point of view the horn emit nearly like if a round horn was inserted inside the square horn (that's a bad image but I hope you see what I mean)
Best regards from Paris, France
Jean-Michel Le Cléac'h
Attachments
is that another way of saying that to perform equally well, the square (or rectangular) horn needs to have a slightly larger area than a round horn?
Hello Jean-Michel,
Think this is a very clever way of easy explaining what happens. If I understand you right this also speaks in favor of your and Voigt´s preferences when doing round to square conversion.
These are Voigt´s words from the patent(-27):
David,
Must be hard to apply the above in Hornresp?
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Hello Andrew,
That's hard to say but IMHO it's probable, both from the 2 points of view : loading and directivity.
Best regards from Paris, France
Jean-Michel Le Cléac'h
That's hard to say but IMHO it's probable, both from the 2 points of view : loading and directivity.
Best regards from Paris, France
Jean-Michel Le Cléac'h
Hi Lars,
It would not be difficult to do, but consistent with conventional practice I prefer to use the actual area given by the horn expansion law. I would rather not make arbitrary adjustments based on the shape of the cross-sectional area. It might be relatively straightforward for a square, but what about for a rectangle having an aspect ratio of say 3:1? How should that area be adjusted?
Kind regards,
David
Hi David,
Just for fun I simmed my previous Onken BR with Altec 414. The combined response is in the pdf. Doesn´t confirm with IRL measurments tha looks more like constant directivty. Did I do something wrong in the sims. EDIT: Just realized that the 1cm thick, heavy felt damping on all walls might have something to do with it.
I also simmed my vented horns. Can I combine "directivity 0 degrees" with "combined" and that way get a realistic response?
Just for fun I simmed my previous Onken BR with Altec 414. The combined response is in the pdf. Doesn´t confirm with IRL measurments tha looks more like constant directivty. Did I do something wrong in the sims. EDIT: Just realized that the 1cm thick, heavy felt damping on all walls might have something to do with it.
I also simmed my vented horns. Can I combine "directivity 0 degrees" with "combined" and that way get a realistic response?
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Hi Lars,
The Hornresp "Combined Response" tool calculates the combined power response. Your measurements presumably show the combined pressure response, which will be somewhat different at higher frequencies due to the increasing directivity of the direct radiator driver diaphragm.
"Combined Response" calculates the combined power response of two sources whereas "0 Degrees Off-Axis" shows the pressure response of a single source. Because of these differences, manually combining the two responses in the way that you suggest is unlikely to give a particularly realistic result.
Kind regards,
David
The Hornresp "Combined Response" tool calculates the combined power response. Your measurements presumably show the combined pressure response, which will be somewhat different at higher frequencies due to the increasing directivity of the direct radiator driver diaphragm.
"Combined Response" calculates the combined power response of two sources whereas "0 Degrees Off-Axis" shows the pressure response of a single source. Because of these differences, manually combining the two responses in the way that you suggest is unlikely to give a particularly realistic result.
Kind regards,
David
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