Excel Workbook Request
Hi David,
Please send me a copy of the MS/Excel Workbook for LeC/HF. I want to have at the math you are using.
Regards,
Bill
Hi David,
Please send me a copy of the MS/Excel Workbook for LeC/HF. I want to have at the math you are using.
Regards,
Bill
Hi Bill and soongsc,
Even though the results of my investigations were presented using Excel charts, all the calculations were done in a development version of Hornresp, with the data being exported to Excel in *.csv files. To implement the new method in Excel would require a VBA macro to be incorporated into the Workbook. I have not done this - the routine was simply added directly into Hornresp.
A copy of the Hornresp VB6 code relating to the new method is attached. The variable names may seem a bit strange - I will leave it to you to work out what it all means 🙂.
Kind regards,
David
Can someone help my with the dimensioning of a 150hz horn. I'm planning to use the monacor Ku-516 driver with it. It goes down to 160hz. I will be crossed as low as possible(around 250hz i hope).
I welcome any input on this.
I welcome any input on this.
Will Wrap
Hi David,
Thanks for sharing your code,
Will send it back in an Excel wrapper (.xlam)
Regards,
Bill
Hi David,
Thanks for sharing your code,
Will send it back in an Excel wrapper (.xlam)
Regards,
Bill
Is this really realistic? 200Hz is 100cm dia. To much work for that driver isn´t it? Use Hornresp to get profile either you go round, petal or square.
Hi Everyone,
Hornresp Version 28.50 has just been released. It includes the Le Cléac'h horn "perfect axisymmetric profile" option.
Kind regards,
David
Attachments
Hi Bill,
A couple of additional comments regarding the code:
1. To simplify things, the two statements R1 = Sqr(S1 / Pi) and ER(0) = R1 can be replaced by the single statement ER(0) = Sqr(S1 / Pi).
(In Visual Basic Sqr rather than Sqrt is the square root function).
2. EA(0) = AT / 180 * Pi (given as EA(0) = frmMain.txtHp(15) / 180 * Pi) is not really required.
The Hornresp exported data shows X and Y coordinates and flare tangent angle Fta. The AT value rather than zero is given for Fta at X = 0 simply for the sake of completeness.
Fta values are included so that the user can truncate the horn mouth at the angle they desire, usually somewhere around 180 degrees. Values up to 360 degrees are listed - see lec.txt attached.
Kind regards,
David
Function Preliminaries
Thanks David,
Some preliminaries follow:
Regards,
Bill
' Declare Compile Options
Option Explicit
Option Base 0
Option Compare Text
'
' Declare Constants
Public Const pid4 As Double = Pi / 4 'Quarter Pi
Public Const pim2 As Double = 2 * Pi 'Double Pi
Public Const c_cm As Double = 34399 'Sound Velocity in Air: cm/sec in air @ 20 °C & 50% RH
Public Const c_in As Double = c_cm / 2.54 'Sound Velocity in Air: in/sec in air @ 68 °F & 50% RH
Public Const cmS As String = "cm" ' CentiMeter Unit of Measure used
Public Const inS As String = "in" ' Inch Unit of Measure used
'
' Argument List
Public T As Double 'Salmon's Shape Parameter
Public Fc As Double 'Cut-Off Frequency (Hz)
Public Rt As Double 'Throat Radius (cm or in)
Public dL As Double 'Length Increment
Public UM As String * 2 'Unit of Measure "cm" or "in"
' Nomenclature/Variable Changes
' R1 -> Rt
' S1 -> St
' Incr -> dL
' F12 -> Fc
Public Function McBLeC(T, Fc, Rt, dL, UM) As Range ' Returns Vectors EL(N), ER(N) & EA(N)
'
'
'
'
' (more later)
'
'
'
'
End Function
Thanks David,
Some preliminaries follow:
Regards,
Bill
' Declare Compile Options
Option Explicit
Option Base 0
Option Compare Text
'
' Declare Constants
Public Const pid4 As Double = Pi / 4 'Quarter Pi
Public Const pim2 As Double = 2 * Pi 'Double Pi
Public Const c_cm As Double = 34399 'Sound Velocity in Air: cm/sec in air @ 20 °C & 50% RH
Public Const c_in As Double = c_cm / 2.54 'Sound Velocity in Air: in/sec in air @ 68 °F & 50% RH
Public Const cmS As String = "cm" ' CentiMeter Unit of Measure used
Public Const inS As String = "in" ' Inch Unit of Measure used
'
' Argument List
Public T As Double 'Salmon's Shape Parameter
Public Fc As Double 'Cut-Off Frequency (Hz)
Public Rt As Double 'Throat Radius (cm or in)
Public dL As Double 'Length Increment
Public UM As String * 2 'Unit of Measure "cm" or "in"
' Nomenclature/Variable Changes
' R1 -> Rt
' S1 -> St
' Incr -> dL
' F12 -> Fc
Public Function McBLeC(T, Fc, Rt, dL, UM) As Range ' Returns Vectors EL(N), ER(N) & EA(N)
'
'
'
'
' (more later)
'
'
'
'
End Function
Thanks Bill.
I have downloaded copies and will study them with great interest.
Kind regards,
David
Hi Bill,
I am particularly intrigued by your Note 3 - "For circular horns, wave front element area need not be calculated, just wave front length Rs. This approach will reduce calculation time."
Given horn cutoff frequency fc, flare parameter T, throat radius Rt, and assuming a plane wavefront at the throat (Art = 0) how is the isophase wavefront length Rs calculated at distance Ls along the horn?
Have you perhaps assumed in making your comment that the surface area of a plane circular disk of diameter CL is the same as the surface area of a convex circular disk (ie isophase wavefront) having a total convex curve length of CL? Unfortunately this is not the case.
Thanks and kind regards,
David
I am particularly intrigued by your Note 3 - "For circular horns, wave front element area need not be calculated, just wave front length Rs. This approach will reduce calculation time."
Given horn cutoff frequency fc, flare parameter T, throat radius Rt, and assuming a plane wavefront at the throat (Art = 0) how is the isophase wavefront length Rs calculated at distance Ls along the horn?
Have you perhaps assumed in making your comment that the surface area of a plane circular disk of diameter CL is the same as the surface area of a convex circular disk (ie isophase wavefront) having a total convex curve length of CL? Unfortunately this is not the case.
Thanks and kind regards,
David
Thanks Bill.
I have made a slight refinement to the new method. It makes no practical difference to the results, but does replace an approximation with an exact solution.
Previously with the new method, the revolved surface area of the outer element of the isophase wavefront was determined by multiplying the length of the outer element circular arc by the circumference of a circle having a radius equal to the perpendicular distance from the horn axis to the MID-POINT of the outer element circular arc.
Now the revolved surface area of the outer element of the isophase wavefront is determined by multiplying the length of the outer element circular arc by the circumference of a circle having a radius equal to the perpendicular distance from the horn axis to the geometric centre or CENTROID of the outer element circular arc.
The new refinement means that the calculated revolved surface area of the outer element is now exactly correct. Previously it was just a good approximation - because the arc angle was small, the error was not significant.
The centroid of a circular arc of radius R and central angle 2 * A (radians) is located on the bisecting radius at a distance R * Sin(A) / A from the centre of the circle.
I have attached a copy of my latest code for your information. Assuming that it is not possible to directly solve for the outer element, I think that the results generated by this new code are probably as accurate as can reasonably be achieved, since all other simplifying approximations have now been removed.
Jean-Michel has been sent a copy of the latest code. The refinement has been added to Hornresp.
Kind regards,
David