The Subwoofer DIY Page
Horn Folding Spreadsheets
09 November 2018

Folding a new bass horn design or adjusting the dimensions of an existing design to meet a specific requirement can be somewhat of a challenge and prone to error.  To make the process easier and to avoid errors as much as possible, I've created a number of different Excel workbooks that can assist with the folding process. All of them should be considered as "works in progress" as I'm continually adding new features and of course fixing the odd bugs that I come across, so always make sure to check here for the latest version before using any of these workbooks.  Some of them I've actually used to design and build my own subwoofers (the best way to confirm that the workbook in question works), and in those cases I've included a link to the project sin question.  If you have any questions about the spreadsheets, please post them to the DIYAudio Subwoofers forum using the provided link below, thanks!

http://www.diyaudio.com/forums/subwoofers/171747-spreadsheet-folded-horn-layouts.html

boxplan-tham

BOXPLAN-THAM
Current Version: 3.6
This workbook can be used to design a tapped horn with a "THAM" style fold.  I used an earlier version of this workbook to design my POC2 tapped horn. The spreadsheet allows for the design of both single and dual-expansion tapped horns.  The workbook contains optimization and export routines.  To use it, you'll need to enter the driver and desired box dimensions, then hit the "Optimize" button until the error cell reads zero (or keeps oscillating around some small numbers). Then update the file location and driver parameters at the bottom of the spreadsheet and use the "Export" button to export a file which you can then import into Hornresp for further analysis.

boxplan-mht

BOXPLAN-MTH
Current Version: 2.4
This workbook can be used to design a tapped horn with a "MTH-30" style fold.  The MTH-30 fold is an easy one to do, but it only supports single expansion designs, which does limit its use a bit.  The workbook contains optimization and export routines.  To use it, you'll need to enter the driver and desired box dimensions, then hit the "Optimize" button until the error cell reads zero (or keeps oscillating around some small numbers). Then update the file location and driver parameters at the bottom of the spreadsheet and use the "Export" button to export a file which you can then import into Hornresp for further analysis.

boxplan-alt

BOXPLAN-MTHALT
Current Version: 1.3
This workbook can be used to design a tapped horn with an alternate version of "MTH-30" style fold, where the mouth is placed on a different side of the box. The MTH-30 fold is an easy one to do, but it only supports single expansion designs, which does limit its use a bit.  Currently the workbook does not contain any optimization and export routines.  To use it, you'll need to manually enter the driver box and panel dimensions that you'd like to use, along with the expansion angles, then modify them until the "Err" values are as low as possible.  The horn's expansion is displayed as a guide.  Once you have completed this, copy the displayed Hornresp parameters to your Hornresp sim for the horn.

boxplan-mltl 

BOXPLAN-MLTL
Current Version: 1.2
This workbook can be used to design a simple mass-loaded transmission line (MLTL) style vented subwoofer, with the vent placed at the narrow end.  I used this workbook to design my "Boom Unit" subwoofer and my "POC6" PA bass unit. The workbook contains optimization and export routines.  To use it, you'll need to enter the driver, and desired box dimensions, then hit the "Optimize" button until the error cell reads the lowest number possible. Then update the file location and driver parameters at the bottom of the spreadsheet and use the "Export" button to export a file which you can then import into Hornresp for further analysis. 

boxplan-ss 

BOXPLAN-SS
Current Version: 6.3
This workbook can be used to design a tapped horn with an "SS"style fold, and include cone compensatin if necessary. I used this workbook to design my my POC3 tapped horn and POC4 tapped horn. The workbook does not currently contain optimization and export routines.  To use it, you'll need to manually enter the driver box and panel dimensions that you'd like to use, along with the expansion angles, then modify them until the "Err" values are as low as possible.  The horn's expansion is displayed as a guide. Once you have completed this, copy the displayed Hornresp parameters to your Hornresp sim for the horn.  

boxplan-ss 

BOXPLAN-SS (with optimization)
Current Version: 8.1
This workbook can be used to design a tapped horn with an "SS"style fold. This version of the workbook contains optimization routines, and a number of bugs existing in v6.3 have been corrected. I suggest using this workbook if you don't plan to or need to include cone compensation in the actual path.  Tho use it, you'll need to enter the driver dimensions, the desired box dimensions and the desired values for S1 and S5, then hit the "Optimize" button until the error cell reads zero. Then update the file location and driver parameters at the bottom of the spreadsheet and use the "Export" button to export a file which you can then import into Hornresp for further analysis. 

boxplan-vbslot 

BOXPLAN-VBSLOT
Current Version: 1.3
This workbook can be used to design a sime slot-loaded vented subwoofer. The workbook does not currently contain optimization and export routines.  To use it, you'll need to manually enter the driver box and panel dimensions that you'd like to use. The workbook then provides relevant details such as net box size, vent length and cross-sectional area. 

BOXPLAN-Othorn

BOXPLAN-OTHORN
Current Version: 1.3
This workbook can be used to design a tapped horn with a "Othorn" style fold.  The spreadsheet allows for the design parabolic (default), conical or exponential expansion, the latter two being approximated by parabolic segments. A simulation of the actual Othorn produced by using this workbook shows a frequency response that is very similar to that measured for the Othorn. The workbook contains optimization and export routines.  To use it, you'll need to enter the driver dimensions, desired box dimensions, desired values for S2 and S5, then hit the "Optimize" button until the error cell reads the lowest number possible. Then update the file location and driver parameters at the bottom of the spreadsheet and use the "Export" button to export a file which you can then import into Hornresp for further analysis.

 

BOXPLAN-WBIN
Current Version: 0.4 (beta)
This workbook can be used to design a "W-bin" type of front-loaded horn. The workbook contains optimization and export routines.  To use it, you'll need to enter the driver dimensions, desired box dimensions, desired values for the horn expansion and a few internal panel dimensions, then hit the "Optimize" button until the error cell reads the lowest number possible. Then update the file location and driver parameters at the bottom of the spreadsheet and use the "Export" button to export a file which you can then import into Hornresp for further analysis.

  BOXPLAN-CYCLOPS
Current Version: 0.3 (beta)
This workbook can be used to design a "Cyclops" type of tapped horn with straight segments (the last section is flared however). The workbook contains optimization and export routines.  To use it, you'll need to enter the driver dimensions, desired box dimensions, desired values for certain horn segments, then hit the "Optimize" button until the error cell reads the lowest number possible. Then update the file location and driver parameters at the bottom of the spreadsheet and use the "Export" button to export a file which you can then import into Hornresp for further analysis.  

  BOXPLAN-ROAR
Current Version: 0.3 (beta)
This workbook can be used to design a "ROAR" type of tapped horn. The workbook contains optimization and export routines.  To use it, you'll need to enter the driver dimensions, desired box dimensions, the size of the offset for the driver baffle, then hit the "Optimize" button until the error cell reads the lowest number possible. Then update the file location and driver parameters at the bottom of the spreadsheet and use the "Export" button to export a file which you can then import into Hornresp for further analysis.

  BOXPLAN-SPLANAR
Current Version: 0.4 (beta)
This workbook can be used to design a planar type of compound horn. The workbook contains optimization and export routines.  To use it, you'll need to enter the driver dimensions, desired box dimensions, the size of the offset for the driver baffle, and the size of the baffle, then hit the "Optimize" button until the error cell reads the lowest number possible. Then update the file location and driver parameters at the bottom of the spreadsheet and use the "Export" button to export a file which you can then import into Hornresp for further analysis. 

  BOXPLAN-TL1
Current Version: 0.1 (beta)
This workbook can be used to design a straight TL, using a fold that is very popular with the car audio crowd. The workbook contains optimization and export routines.  To use it, you'll need to enter the driver dimensions, desired box dimensions, the size of the offset for the driver baffle, and the size of the baffle, then hit the "Optimize" button until the error cell reads the lowest number possible. Then update the file location and driver parameters at the bottom of the spreadsheet and use the "Export" button to export a file which you can then import into Hornresp for further analysis.  

  BOXPLAN-TL2
Current Version: 0.1 (beta)
This workbook can be used to design a straight TL, using a better fold than the TL1 fold as it allows for much more flexibility in positioning the driver at a useful offset down the line.The workbook contains optimization and export routines.  To use it, you'll need to enter the driver dimensions, desired box dimensions, the size of the offset for the driver baffle, then hit the "Optimize" button until the error cell reads the lowest number possible. Then update the file location and driver parameters at the bottom of the spreadsheet and use the "Export" button to export a file which you can then import into Hornresp for further analysis.   

  BOXPLAN-MLTL2
Current Version: 0.1 (beta)
This workbook can be used to design a mass-loaded transmission line (MLTL) style vented subwoofer, with a folded vent..  To use it, you'll need to enter the driver dimensions, desired box dimensions, the size of the offset for the driver baffle, then hit the "Optimize" button until the error cell reads the lowest number possible. Then update the file location and driver parameters at the bottom of the spreadsheet and use the "Export" button to export a file which you can then import into Hornresp for further analysis.   

In Development:
These workbooks that are flagged as "beta" should be considered as still under development, so expect a few bugs. Panel dimensions should be checked closely, for example. If you use them and come across any bugs, please report them to me thanks, using the message thread listed at the top of this page

Instructions:
Probably the hardest part of using any of these workbooks is entering the driver's parameters, as Hornresp by default needs the driver's BL, Cms and Mmd. Mmd is rarely quoted for a driver (Mms sometimes is but that's not the same as Mmd). So, to use the spreadsheet, you may have to follow the steps below.

  1. Enter the physical dimensions for the driver that you want to use in the "Driver Dimension" section near the top of the first spreadsheet in the workbook.

  2. Enter the physical dimensions of the box that you want to use in the appropriate section of the first spreadsheet in the workbook.

  3. Enter the thickness of the wood that you plan to use to build the box. In some of the workbooks, you can select different thicknesses for different panels.

  4. In some of the workbooks, you can adjust the depth of the baffle inset, or the position of the driver on the baffle. Do this if necessary.

  5. Under Hornresp parameters, enter the cross-sectional area of the sections or their lengths where allowed to do so.

  6. If the workbook has an Optimize button, hit it until all the numbers in red read "0.00". The layout of the box is now optimized. If it does not have an Optimize button, adjust the lengths of each panel and the expansion angle or angles until the expansion graph is smooth and all numbers in red read "0.00" or very close to zero.

  7. Under "Filename", change the desired location of the export file. The default location for HornResp is "C:\Hornresp\Import".

  8. Hit the "Export!" button.

  9. In Hornresp, select "File..Import..Hornresp Record" and import the file you created in Step 7

  10. Double-click on "Sd" and enter the driver's t/s parameters, and click Ok. Hornresp will calculate Bl, Cms, Mmd, and Rms.

  11. In the workbook, enter the driver's parameters (Sd, Bl, Cms, Rms, Mmd, Le, Re) that Hornresp calculated in the table at the bottom of the first spreadsheet, and hit "Export!" again.

  12. In Hornresp, select "Tools..Loudspeaker Wizard" to bring up the Loudspeaker Wizard.

  13. Press F6. This will load the new version of the Import file.

  14. In Hornresp's "Loudspeaker Wizard", review the simulated response of your design by selecting "Power" from the pulldown menu.

  15. Repeat steps 2,4,5,6,8 and 13 until you get a result that you like.

  16. Take the panel dimensions from the "Box Design" section of spreadsheet, cut the panels, build your box and enjoy.

  17. Use the "Guides" feature to assist with the layout of any internal panels in the box.

Brian Steele
09 November 2018