Hornresp

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tb46

Member
Joined 2006
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,
 
D

David McBean

Member
Joined 2007
hornresp.net
mwmkravchenko said:
I agree David.

Especially in regards to compression drivers, working directly with a flare rate and a diameter is the simplest method.
Click to expand...

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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D

David McBean

Member
Joined 2007
hornresp.net
tb46 said:
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.
Click to expand...

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
 
Kravchenko_Audio

Kravchenko_Audio

Member
Joined 2002
kravchenko-audio.com
Paid Member
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
Click to expand...

:yes:
 
DrDyna

DrDyna

Member
Joined 2007
mwmkravchenko said:
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.
Click to expand...

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*
 
W

whgeiger

Member
Joined 2004
Horn Bend Acoustics

mwmkravchenko said:
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.
Click to expand...

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
 

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W

whgeiger

Member
Joined 2004
Update

whgeiger said:
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
Click to expand...

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
 
M

more10

Member
Joined 2011
What about an algorithm to calculate a smooth transition from the following input parameters?
  • Compression driver exit radius
  • Compression driver exit flare tangent angle
  • Horn throat radius
  • Horn throat flare tangent angle
  • Adaptor length
Kind regards,
David
Click to expand...

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)
The adaptor becomes as long as it needs to be.

Maybe you are interested in including the "linearly varying cutoff frequency exponential" horn flare in Hornresp?
Click to expand...

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.
 
D

David McBean

Member
Joined 2007
hornresp.net
more10 said:
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)
The adaptor becomes as long as it needs to be.

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.
Click to expand...

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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