Hi Kevin,
Using the raw data provided by Martin:
S2 = 7088.22 sq cm
L12 = 45.00 cm
F12 = 160.00 hertz
T = 0.80
S1 and Fta become:
S1 = 269.80 sq cm (diameter = 7.30 in)
Fta = 93.70 degrees
I have assumed that Martin is referring to the diameter of the mouth opening including rollback, and that he is using Jean-Michel’s 2007 spreadsheet.
Kind regards,
David
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Hi David,
Thank you for your input. Those results are very close to what I ended up with before I tried to model the 160 based on the 1.5 inch throat that Martin mentions. The minor differences are that I used the throat area calculated for the Fostex at 260.16 and had not yet figured how to limit L12 to 45 cm. My L12 still came in at 45.6 cm and I had a Fta of 93.8.
My feeling was that I thought those numbers didn't represent what was pictured on his website. At this point I think what I am going to do is use the numbers to draw out the last few inches of the profile so I can actually see it.
More importantly, I feel now that I need to make some decisions about what I am willing to compromise on. I need to understand more about what the returns are going to be by possibly undertaking the fabrication of a horn that will be larger and have a fuller profile than the Azura or not.
I have modeled several profiles using 150 and 160 cutoffs and have made adjustments to see the difference in scale when manipulating T factor and aiming for different Fta angles. My feeling is that I might be able to live with the scale of a 150 or 160 modeled with a T of .5 and a Fta of about 101 to 112 degrees. Until I can grasp how these variations are affecting the overall performance of the horn I'm still fishing... unless I just copy an existing profile based on reputation or feedback. Jean-Michel's recommendation of the lower T factor for cone drivers is stuck in the back of my mind right now and influencing my thinking. I suppose that is another reason for not just jumping into an Azura clone.
I think the next thing I want to do is to calculate a rear chamber and then study some analysis features in Hornresp so I can get an idea of how the different horns will perform. I was thinking of using WinISD to do this, unless someone has a better suggestion, and starting out with a sealed rear chamber tuned the same as the cutoff frequency.
Many thanks
Kevin
Thank you for your input. Those results are very close to what I ended up with before I tried to model the 160 based on the 1.5 inch throat that Martin mentions. The minor differences are that I used the throat area calculated for the Fostex at 260.16 and had not yet figured how to limit L12 to 45 cm. My L12 still came in at 45.6 cm and I had a Fta of 93.8.
My feeling was that I thought those numbers didn't represent what was pictured on his website. At this point I think what I am going to do is use the numbers to draw out the last few inches of the profile so I can actually see it.
More importantly, I feel now that I need to make some decisions about what I am willing to compromise on. I need to understand more about what the returns are going to be by possibly undertaking the fabrication of a horn that will be larger and have a fuller profile than the Azura or not.
I have modeled several profiles using 150 and 160 cutoffs and have made adjustments to see the difference in scale when manipulating T factor and aiming for different Fta angles. My feeling is that I might be able to live with the scale of a 150 or 160 modeled with a T of .5 and a Fta of about 101 to 112 degrees. Until I can grasp how these variations are affecting the overall performance of the horn I'm still fishing... unless I just copy an existing profile based on reputation or feedback. Jean-Michel's recommendation of the lower T factor for cone drivers is stuck in the back of my mind right now and influencing my thinking. I suppose that is another reason for not just jumping into an Azura clone.
I think the next thing I want to do is to calculate a rear chamber and then study some analysis features in Hornresp so I can get an idea of how the different horns will perform. I was thinking of using WinISD to do this, unless someone has a better suggestion, and starting out with a sealed rear chamber tuned the same as the cutoff frequency.
Many thanks
Kevin
Hello,
The relation between the maximal radius of a complete axisymetric Le Cleac'h horn and its cut-off frequency is given by the empirical formula.
max-radius = 96216 / cut_off_frequency
max-radius is in millimeters (1 inch = 25.4 millimeters)
cut_off_frequency is in Hertz
Both the throat diameter and the T value have a limited influence on the maximal radius of the Le Cléac'h horn.
Fc (Hz)....radius (mm)
100Hz ...... 962mm
200Hz ...... 481mm
300Hz ...... 321mm
400Hz ...... 241mm
500Hz ...... 192mm
600Hz ...... 160mm
700Hz ...... 137mm
800Hz ...... 120mm
900Hz ...... 107mm
1000Hz ...... 96mm
1100Hz ...... 87mm
1200Hz ...... 80mm
1300Hz ...... 74mm
1400Hz ...... 69mm
1500Hz ...... 64mm
1600Hz ...... 60mm
Often, due to some demand for horns having reduced size, commercial builders have to reduce somewhat the maximal diameter of the Le Cléac'h horn. In order to do that, they truncate a bit the horn an apply some empirical rounding of the profile at the new mouth.
Best regards from Paris, France
Jean-Michel Le Cléac'h
The relation between the maximal radius of a complete axisymetric Le Cleac'h horn and its cut-off frequency is given by the empirical formula.
max-radius = 96216 / cut_off_frequency
max-radius is in millimeters (1 inch = 25.4 millimeters)
cut_off_frequency is in Hertz
Both the throat diameter and the T value have a limited influence on the maximal radius of the Le Cléac'h horn.
Fc (Hz)....radius (mm)
100Hz ...... 962mm
200Hz ...... 481mm
300Hz ...... 321mm
400Hz ...... 241mm
500Hz ...... 192mm
600Hz ...... 160mm
700Hz ...... 137mm
800Hz ...... 120mm
900Hz ...... 107mm
1000Hz ...... 96mm
1100Hz ...... 87mm
1200Hz ...... 80mm
1300Hz ...... 74mm
1400Hz ...... 69mm
1500Hz ...... 64mm
1600Hz ...... 60mm
Often, due to some demand for horns having reduced size, commercial builders have to reduce somewhat the maximal diameter of the Le Cléac'h horn. In order to do that, they truncate a bit the horn an apply some empirical rounding of the profile at the new mouth.
Best regards from Paris, France
Jean-Michel Le Cléac'h
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Kevin,
You begin in the wrong end! You have to adjust throat-area to get an acceptable high end response and will need to use some compression to get it acceptable. 2:1 could be a good start. Then accept whatever value L12 is.
About rear chamber you get enough indications in HR. But the exact volume can NEVER be calculated. You have to do it empirically starting from what HR indicates. Often rear chamber should be tuned a tad lower than the horn.
You begin in the wrong end! You have to adjust throat-area to get an acceptable high end response and will need to use some compression to get it acceptable. 2:1 could be a good start. Then accept whatever value L12 is.
About rear chamber you get enough indications in HR. But the exact volume can NEVER be calculated. You have to do it empirically starting from what HR indicates. Often rear chamber should be tuned a tad lower than the horn.
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