Thanks BYRTT and bolserst!
Included is a new version of the spreadsheet with possibility to set "Piston directivity" to "on". This calculates the directivity for a flat piston with set Sd (or manual input of diameter).
This is with 30 TC9s in a 2.6 m high room:



This plot is new, shows the phase inversion for off-axis response. Only complete inversions (180 degrees) are handled by the excelsheet, I have not implemented custom off-axis phase support.
As usual: download the *.mp4 and rename to *.zip and then unzip 🙂 And if you find any errors, please tell me!
/Anton
Included is a new version of the spreadsheet with possibility to set "Piston directivity" to "on". This calculates the directivity for a flat piston with set Sd (or manual input of diameter).
This is with 30 TC9s in a 2.6 m high room:



This plot is new, shows the phase inversion for off-axis response. Only complete inversions (180 degrees) are handled by the excelsheet, I have not implemented custom off-axis phase support.
As usual: download the *.mp4 and rename to *.zip and then unzip 🙂 And if you find any errors, please tell me!
/Anton
Attachments
Looks like the piston directivity calculations are working properly. 
Two minor issues:
- For the “With Directivity” calculations on the [Resulting SPL] tab, the secondary floor reflection increment is getting turned on with the ceiling reflection flag rather than the secondary reflection flag
- When piston directivity is turned off, the phase reversals at high frequency due to directivity are still being included in the calculations

Two minor issues:
- For the “With Directivity” calculations on the [Resulting SPL] tab, the secondary floor reflection increment is getting turned on with the ceiling reflection flag rather than the secondary reflection flag
- When piston directivity is turned off, the phase reversals at high frequency due to directivity are still being included in the calculations
Sorry for the late reply.Looks like the piston directivity calculations are working properly.
Two minor issues:
- For the “With Directivity” calculations on the [Resulting SPL] tab, the secondary floor reflection increment is getting turned on with the ceiling reflection flag rather than the secondary reflection flag
- When piston directivity is turned off, the phase reversals at high frequency due to directivity are still being included in the calculations
Well caught, here is an updated spreadsheet with fixes of the two mentioned problems. Rename to *.zip and unpack to access.
/Anton