Hi David,
Post #5180: "... for the adaptor to match the actual physical flare tangent angles of the compression driver and the horn..."
That's how I do it in a drafting program, it would be nice to have something similar to the Driver Front Volume Calculator for this purpose.
Regards,
Post #5180: "... for the adaptor to match the actual physical flare tangent angles of the compression driver and the horn..."
That's how I do it in a drafting program, it would be nice to have something similar to the Driver Front Volume Calculator for this purpose.
Regards,
I agree David.
Especially in regards to compression drivers, working directly with a flare rate and a diameter is the simplest method.
Hi Mark,
Specifying a flare tangent angle rather than an exponential cutoff frequency as the input parameter makes the method more general, in that it can then be applied to all horn types - not just to exponential horns. For example, with the same 2 inch throat diameter, a 250Hz exponential horn has a different throat entry angle to a 250Hz T = 0.7 Le Cléac’h horn. The exponential horn has an entry angle of 6.62 degrees whereas the Le Cléac’h horn has an entry angle of 4.64 degrees.
Kind regards,
David
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That's how I do it in a drafting program, it would be nice to have something similar to the Driver Front Volume Calculator for this purpose.
Hi Oliver,
The only difference being that the output from the Driver Front Volume tool can be used as input to a simulation, whereas the output from a "throat adaptor calculator" could not .
For the Ap1 setting, Hornresp assumes a conical flare throat adaptor of throat area Ap1, mouth area S1, and length Lpt.
Kind regards,
David
Specifying a flare tangent angle rather than an exponential cutoff frequency as the input parameter makes the method more general, in that it can then be applied to all horn types - not just to exponential horns. For example, with the same 2 inch throat diameter, a 250Hz exponential horn has a different throat entry angle to a 250Hz T = 0.7 Le Cléac’h horn. The exponential horn has an entry angle of 6.62 degrees whereas the Le Cléac’h horn has an entry angle of 4.64 degrees.
Kind regards,
David
Horn folding in AutoCAD
Has anybody looked into this?
Setting up an autofold is very interesting.
And there are opensource drafting programs that can take scripts.
Hornresp will generate the data.
I'm just not fluent enough with some of this stuff to take a stab at it.
Has anybody looked into this?
Setting up an autofold is very interesting.
And there are opensource drafting programs that can take scripts.
Hornresp will generate the data.
I'm just not fluent enough with some of this stuff to take a stab at it.
Horn folding in AutoCAD
Has anybody looked into this?
Setting up an autofold is very interesting.
And there are opensource drafting programs that can take scripts.
Hornresp will generate the data.
I'm just not fluent enough with some of this stuff to take a stab at it.
Wouldn't that be a kicker, supply a constrained maximum dimension and software just plops out a completed 3d rendering.
I have faith that the audio industry will be pulled kicking and screaming into the 90s soon enough. *runs away*
Horn Bend Acoustics
I developed an Excel Spreadsheet back in 2003 using the findings of Nederveen, Keefe and Benade (Circa 1980’s and earlier). See attached PDF file for a summary of their work on this matter as it relates to the design of musical instrument horns. While the application here is different, their findings never the less, apply equally well here too. To generate a drawing in AutoCAD requires only that the spreadsheet data be encapsulated in the appropriate drawing commands and then copied into a macro text file for execution. Use of string formula in Excel makes this task fairly straight forward.
Look at a horn/duct bends/folds as a low pass filter whose frequency response characteristics are determined by its transverse dimensions and bend/fold severity set by the size of the inside radius of curvature. Due to these relationships, you will soon discover the need for passage bifurcation as well. Of course, the only reason for doing this is to reduce the foot print of a low or mid frequency horn; i.e., horns with an [fc] < 1000 Hz. These issues were explored much earlier by Rayleigh in Volume II of his book entitled “The Theory of Sound” (Circa 1896).
Regards,
WHG
Horn folding in AutoCAD
Has anybody looked into this?
Setting up an autofold is very interesting.
And there are opensource drafting programs that can take scripts.
Hornresp will generate the data.
I'm just not fluent enough with some of this stuff to take a stab at it.
I developed an Excel Spreadsheet back in 2003 using the findings of Nederveen, Keefe and Benade (Circa 1980’s and earlier). See attached PDF file for a summary of their work on this matter as it relates to the design of musical instrument horns. While the application here is different, their findings never the less, apply equally well here too. To generate a drawing in AutoCAD requires only that the spreadsheet data be encapsulated in the appropriate drawing commands and then copied into a macro text file for execution. Use of string formula in Excel makes this task fairly straight forward.
Look at a horn/duct bends/folds as a low pass filter whose frequency response characteristics are determined by its transverse dimensions and bend/fold severity set by the size of the inside radius of curvature. Due to these relationships, you will soon discover the need for passage bifurcation as well. Of course, the only reason for doing this is to reduce the foot print of a low or mid frequency horn; i.e., horns with an [fc] < 1000 Hz. These issues were explored much earlier by Rayleigh in Volume II of his book entitled “The Theory of Sound” (Circa 1896).
Regards,
WHG
Attachments
Update
Update
See my 2012 post for more detail.
http://www.diyaudio.com/forums/multi-way/219656-horns-bend-reflectors-2.html#post3166215
The spreadsheet needs to be updated to incorporate these findings.
WHG
I developed an Excel Spreadsheet back in 2003 using the findings of Nederveen, Keefe and Benade (Circa 1980’s and earlier). See attached PDF file for a summary of their work on this matter as it relates to the design of musical instrument horns. While the application here is different, their findings never the less, apply equally well here too. To generate a drawing in AutoCAD requires only that the spreadsheet data be encapsulated in the appropriate drawing commands and then copied into a macro text file for execution. Use of string formula in Excel makes this task fairly straight forward.
Look at a horn/duct bends/folds as a low pass filter whose frequency response characteristics are determined by its transverse dimensions and bend/fold severity set by the size of the inside radius of curvature. Due to these relationships, you will soon discover the need for passage bifurcation as well. Of course, the only reason for doing this is to reduce the foot print of a low or mid frequency horn; i.e., horns with an [fc] < 1000 Hz. These issues were explored much earlier by Rayleigh in Volume II of his book entitled “The Theory of Sound” (Circa 1896).
Regards,
WHG
Update
See my 2012 post for more detail.
http://www.diyaudio.com/forums/multi-way/219656-horns-bend-reflectors-2.html#post3166215
The spreadsheet needs to be updated to incorporate these findings.
WHG
Erratum
New Link to Referenced PDF
https://hal.inria.fr/file/index/doc...rveen_Dalmont_2011_JAcoustSocAm_submitted.pdf
Update
See my 2012 post for more detail.
http://www.diyaudio.com/forums/multi-way/219656-horns-bend-reflectors-2.html#post3166215
The spreadsheet needs to be updated to incorporate these findings.
WHG
New Link to Referenced PDF
https://hal.inria.fr/file/index/doc...rveen_Dalmont_2011_JAcoustSocAm_submitted.pdf
Hi All,
FYI:
Acoustics of 90 degree sharp bends. Part I: Low-frequency acoustical response
http://perso.univ-lemans.fr/~yauregan/publi/Bend_I.pdf
Acoustics of 90 degree sharp bends. Part II: Low-frequency aeroacoustical response
http://perso.univ-lemans.fr/~yauregan/publi/Bend_II.pdf
https://ccrma.stanford.edu/marl/Coltman/documents/Coltman-1.44.pdf
b
FYI:
Acoustics of 90 degree sharp bends. Part I: Low-frequency acoustical response
http://perso.univ-lemans.fr/~yauregan/publi/Bend_I.pdf
Acoustics of 90 degree sharp bends. Part II: Low-frequency aeroacoustical response
http://perso.univ-lemans.fr/~yauregan/publi/Bend_II.pdf
https://ccrma.stanford.edu/marl/Coltman/documents/Coltman-1.44.pdf
b
What about an algorithm to calculate a smooth transition from the following input parameters?
Kind regards,
- Compression driver exit radius
- Compression driver exit flare tangent angle
- Horn throat radius
- Horn throat flare tangent angle
- Adaptor length
David
I figured out that the Autotech horn has a T of 0.98 and and entry angle of 5.2 degrees. The adapter I had made had an exit angle of 5.3. The algorithm could easily be adapted (thanks for the equations you sent me David). So I have listened to your advice and changed the script. It now accepts
- Compression driver exit radius
- Compression driver exit flare tangent angle (or cutoff frequency)
- Horn throat radius
- Horn throat flare tangent angle (or cutoff frequency)
Maybe you are interested in including the "linearly varying cutoff frequency exponential" horn flare in Hornresp?
I still would like to simulate the adaptor.
The algorithm is still using varying cutoff frequency. Now it uses the angles to figure out entry and exit frequency.
I figured out that the Autotech horn has a T of 0.98 and and entry angle of 5.2 degrees. The adapter I had made had an exit angle of 5.3. The algorithm could easily be adapted (thanks for the equations you sent me David). So I have listened to your advice and changed the script. It now accepts
The adaptor becomes as long as it needs to be.
- Compression driver exit radius
- Compression driver exit flare tangent angle (or cutoff frequency)
- Horn throat radius
- Horn throat flare tangent angle (or cutoff frequency)
I still would like to simulate the adaptor.
The algorithm is still using varying cutoff frequency. Now it uses the angles to figure out entry and exit frequency.
Hi Mårten,
Thanks for the update - glad to hear that the angle equation proved to be useful .
Because of the interest shown in the matter, I will probably eventually include some sort of Throat Adaptor Wizard tool in Hornresp to generate a smooth contour and enable the dimension data to be exported. The inputs would be the ones I originally proposed:
- Compression driver exit radius
- Compression driver exit flare tangent angle
- Horn throat radius
- Horn throat flare tangent angle
- Adaptor length
I won't however be including the ability to simulate the adaptor. The current conical horn approximation should be close enough for all practical purposes.
Just in case anyone was wondering, I won't be including any horn folding tools in Hornresp either .
Kind regards,
David
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Because of the interest shown in the matter, I will probably eventually include some sort of Throat Adaptor Wizard tool in Hornresp to generate a smooth contour and enable the dimension data to be exported. The inputs would be the ones I originally proposed:
Check the algorithm in my script, its in Dropbox.
Horn folding in AutoCAD
Has anybody looked into this?
Setting up an autofold is very interesting.
And there are opensource drafting programs that can take scripts.
Hornresp will generate the data.
I'm just not fluent enough with some of this stuff to take a stab at it.
can it design a tapped horn ???
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can it design a tapped horn ???
I have the AutoCAD script. I believe that it is no longer available for download.
And it looks from the description that script takes the co-ordinates and chops them up into manageable sections. Then folds to a form factor.
If anyone wants to take a look at it drop me a email.
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