/sreten.ARTA for directivity measurements
... pls look here
http://www.diyaudio.com/forums/showthread.php?s=&threadid=76977&perpage=10&highlight=&pagenumber=4
and here
http://www.fesb.hr/~mateljan/arta/AppNotes/AP6_Directivity_und_Polar-Rev01Ger.pdf
Regards
Heinrich
... pls look here
http://www.diyaudio.com/forums/showthread.php?s=&threadid=76977&perpage=10&highlight=&pagenumber=4
and here
http://www.fesb.hr/~mateljan/arta/AppNotes/AP6_Directivity_und_Polar-Rev01Ger.pdf
Regards
Heinrich
I have to agree with sreten on that.
The simulators don't allow for different cone shapes or contours of stiffness. A deep, rigid cone will have a narrower high freq. pattern than a curvilinear cone. Stiffening the apex will increase the upper limit, however it it stiffens too far up the apex, will beam it.
I am doing right now, in fact.
Geoff.
edit. If the beam was down to 10 deg, is a flat baffle going to make it wider? Say 40 degrees. Be handy if it did.
The simulators don't allow for different cone shapes or contours of stiffness. A deep, rigid cone will have a narrower high freq. pattern than a curvilinear cone. Stiffening the apex will increase the upper limit, however it it stiffens too far up the apex, will beam it.
I am doing right now, in fact.
Geoff.
edit. If the beam was down to 10 deg, is a flat baffle going to make it wider? Say 40 degrees. Be handy if it did.
Thank you very much to everyone who replied.
Dear serten, Geoff H, and pinkmouse,
I do realize that models have limitations. And some of the variables may even be of a second or lower order.
I do not expect a quantitative analysis, more of a qualitative one, and insight, if you will. Staying with Richard W. Hamming's qoute "The purpose of computing is insight, not numbers."
Kindest regardes,
M
Dear serten, Geoff H, and pinkmouse,
I do realize that models have limitations. And some of the variables may even be of a second or lower order.
I do not expect a quantitative analysis, more of a qualitative one, and insight, if you will. Staying with Richard W. Hamming's qoute "The purpose of computing is insight, not numbers."
Kindest regardes,
M
M,
The newest versions of my MathCad worksheets are going to show a polar plot of the driver in the enclosure. Right now it is set up as a free field polar plot but it will give the user some idea of how much sound energy is being reflected off the back or side walls and how directional the speaker is as a function of frequency. The polar plot accounts for the driver, port, or TL opening directivity as a function of size and shape and also the rectangular baffle edge sources. This is a work in progress and will continue to be developed. The OB worksheets were made available this weekend and hopefully a few more will follow every week or two depending on my time constraints at home.
The newest versions of my MathCad worksheets are going to show a polar plot of the driver in the enclosure. Right now it is set up as a free field polar plot but it will give the user some idea of how much sound energy is being reflected off the back or side walls and how directional the speaker is as a function of frequency. The polar plot accounts for the driver, port, or TL opening directivity as a function of size and shape and also the rectangular baffle edge sources. This is a work in progress and will continue to be developed. The OB worksheets were made available this weekend and hopefully a few more will follow every week or two depending on my time constraints at home.
Do a search for a tool called ARPE at the FRD consortium.
Alternatively I can send you a spreadsheet if you wish. It is based on The math at Art Ludwig's sound page. Art did a test of modeled vs. actual vs diameter based and found that shape matters very little in the farfield. Shape does matter for how the driver performs outside of the pistonic range, however....
Alternatively I can send you a spreadsheet if you wish. It is based on The math at Art Ludwig's sound page. Art did a test of modeled vs. actual vs diameter based and found that shape matters very little in the farfield. Shape does matter for how the driver performs outside of the pistonic range, however....
One can consider two levels of polar pattern:
First, the estimation based on driver dimensions and enclosure dimentions. Some companies use this information as one criteria for investigating XO points so that dispersion match is good at the XO frequencies. I recall somewhere there was an article that mentioned a ka value, but I somehow can't find it any more.
Second, measured from the driver. This takes into account the cone/dustcap shape, material, etc.
I'm sure there are also analysis tools out there?
First, the estimation based on driver dimensions and enclosure dimentions. Some companies use this information as one criteria for investigating XO points so that dispersion match is good at the XO frequencies. I recall somewhere there was an article that mentioned a ka value, but I somehow can't find it any more.
Second, measured from the driver. This takes into account the cone/dustcap shape, material, etc.
I'm sure there are also analysis tools out there?
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