Somebody asked in the

The often-quoted rule-of-thumb of "1,000,000 / Cone size in inches / dispersion in degrees = frequency in Hz" is a bit crude ,so I thought I'd share instead an Excel spreadsheet I've made for predicting beaming (without resorting to other software I cannot use at work...)

I started making the spreadsheet after reading posts on the subject by forum member @bolserst and doing some further research online. Eventually however, bolserst had to help me out with some of the equations before I could finalise it so all the credit goes to him really. He has also shown in posts on here that the predictions from the underlying equations match very well with actual measured driver directivity.

Hopefully the spreadsheet is simple enough to use but a few pointers:

(1) Download and change file extension from .asc to .xlsx;

(2) make your inputs in cells C4 to C10;

(3) Cell B24 will tell you at what frequency the response is down by -6dB at your specified listening angle;

(4) Cells G33 to G4035 will tell you the beamwidth of your specified size driver as a function of frequency. This can be useful for determining the upper crossover frequency to match the beamwidth of a horn (e.g. the 12P80Nd would match the 80 degrees BW of the TPL-150H at 1,420Hz on an infinite baffle);

(5) Cells H33 to H4035 will tell you what piston area (Sd) driver you would need to achieve your specified listening angle/beamwidth as a function of frequency (e.g. an Sd of 277 cm2 would have the same 80 degrees BW of the TPL-150H at 2,000Hz on an infinite baffle);

(6) Note the remarks in cells K18 andK34 about which info that is not (yet) valid for dipole (including 3, 4 and 5 above) and that I need to work more on (any help would be appreciated). Please note that data in cells A33:F4035 are correct for dipole however (as is graph on 'Beaming' tab) so easy enough to find the power loss as a function of frequency by scrolling down in the spreadsheet;

(7) There are three graphs on their own tabs. The X and Y axis ranges have been cropped to cover the most common type of usage but can be changed by the user if need be (the spreadsheet is unlocked);

(8) The two last tabs 'Coefficients' and 'Slask calc' should be left alone ;

Hopefully someone will find it useful. Any questions, suggestions, corrections, or improvements are more than welcome.

*Best midrange to pair with Beyma TPL-150*thread how to calculate directivity of a driver to match up with a horn. This question is being asked quite often and one I've spent some time trying to figure out for myself.The often-quoted rule-of-thumb of "1,000,000 / Cone size in inches / dispersion in degrees = frequency in Hz" is a bit crude ,so I thought I'd share instead an Excel spreadsheet I've made for predicting beaming (without resorting to other software I cannot use at work...)

I started making the spreadsheet after reading posts on the subject by forum member @bolserst and doing some further research online. Eventually however, bolserst had to help me out with some of the equations before I could finalise it so all the credit goes to him really. He has also shown in posts on here that the predictions from the underlying equations match very well with actual measured driver directivity.

Hopefully the spreadsheet is simple enough to use but a few pointers:

(1) Download and change file extension from .asc to .xlsx;

(2) make your inputs in cells C4 to C10;

(3) Cell B24 will tell you at what frequency the response is down by -6dB at your specified listening angle;

(4) Cells G33 to G4035 will tell you the beamwidth of your specified size driver as a function of frequency. This can be useful for determining the upper crossover frequency to match the beamwidth of a horn (e.g. the 12P80Nd would match the 80 degrees BW of the TPL-150H at 1,420Hz on an infinite baffle);

(5) Cells H33 to H4035 will tell you what piston area (Sd) driver you would need to achieve your specified listening angle/beamwidth as a function of frequency (e.g. an Sd of 277 cm2 would have the same 80 degrees BW of the TPL-150H at 2,000Hz on an infinite baffle);

(6) Note the remarks in cells K18 andK34 about which info that is not (yet) valid for dipole (including 3, 4 and 5 above) and that I need to work more on (any help would be appreciated). Please note that data in cells A33:F4035 are correct for dipole however (as is graph on 'Beaming' tab) so easy enough to find the power loss as a function of frequency by scrolling down in the spreadsheet;

(7) There are three graphs on their own tabs. The X and Y axis ranges have been cropped to cover the most common type of usage but can be changed by the user if need be (the spreadsheet is unlocked);

(8) The two last tabs 'Coefficients' and 'Slask calc' should be left alone ;

Hopefully someone will find it useful. Any questions, suggestions, corrections, or improvements are more than welcome.