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-   -   Spreadsheet for Folded Horn Layouts... (http://www.diyaudio.com/forums/subwoofers/171747-spreadsheet-folded-horn-layouts.html)

Brian Steele 12th August 2010 12:12 AM

Spreadsheet for Folded Horn Layouts...
 
1 Attachment(s)
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 this thread, thanks!

BOXPLAN-THAM
Current Version: 3.4
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-MTH
Current Version: 2.2
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-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
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. 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-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 (with optimization)
Current Version: 7.1
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
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
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.

The latest versions of the workbooks are available at this location:

The Subwoofer DIY Page

Brian Steele 12th August 2010 12:58 AM

One issue that's come up is calculated horn length.

I used the "centerline" method to determine horn length. I've also not included any "end effects" in the calculation. I used the spreadsheet to produce the layout for my POC2 TH. It predicted a horn length of 245cm (as required by HornResp). However, when I measured the TH's lowest resonance frequency, it turned out to be more like 43 Hz, not 40 Hz as predicted by HornResp. Reverse-engineering this in HornResp (i.e. adjusting the path length until the predicted resonance frequency increased to 43 Hz) results in an effective path length of 231 cm, which is much shorter than that given by either the centerline method or the square-root method. Any ideas?

mwmkravchenko 12th August 2010 09:04 AM

You are worried about 3 hz?

For one thing Fs usually goes up when a driver is actually in a horn. The air mass loading inside the box is different than outside. Especially in a tapped horn as compact as yours. Another thing is how well broken in is the driver? That 3 hz should even out After a bit oh exercise.

Playing with the spreadsheet is pretty cool. Still have to figure out the auto function but it seems to do what you designed it for. I'll mess with it some more tonight. I'll punch in a couple other horns.

Now many I have designed are up to S5 in the sections. I have taken for granted that you are simply looking for beginning area, path length and mouth area. Is this correct?

One question is if you could set it up with sections as Hornresp could you then calculate horns with a partial negative flare rate? Lots of my designs seem to function better with a section that acts more like a resonator than a true horn flare.

Mark

Brian Steele 12th August 2010 01:42 PM

Quote:

Originally Posted by mwmkravchenko (http://www.diyaudio.com/forums/subwoofers/171747-spreadsheet-folded-horn-layouts-post2270311.html#post2270311)
You are worried about 3 hz?

Yup :). More correctly, I'm worried about a measured result that's 7.5% off the predicted result.


Quote:

Originally Posted by mwmkravchenko (http://www.diyaudio.com/forums/subwoofers/171747-spreadsheet-folded-horn-layouts-post2270311.html#post2270311)
For one thing Fs usually goes up when a driver is actually in a horn. The air mass loading inside the box is different than outside. Especially in a tapped horn as compact as yours. Another thing is how well broken in is the driver? That 3 hz should even out After a bit oh exercise.

I'm concernined about the resonance frequency of the horn, not the driver. It's represented by the first impedance minimum and it's independent of driver characteristics. It's solely dependent on the characteristics of the horn.


Quote:

Originally Posted by mwmkravchenko (http://www.diyaudio.com/forums/subwoofers/171747-spreadsheet-folded-horn-layouts-post2270311.html#post2270311)
Playing with the spreadsheet is pretty cool. Still have to figure out the auto function but it seems to do what you designed it for. I'll mess with it some more tonight. I'll punch in a couple other horns.

Now many I have designed are up to S5 in the sections. I have taken for granted that you are simply looking for beginning area, path length and mouth area. Is this correct?

Not quite. I found a way to mathematically describe the size and shape of the tapered and stepped horn illustrated in the graph and relate those to beginning area, path length and mouth area. The technique can be theoretically expanded to include other parameters such as varying flare rate, but the important thing is to be able to mathematically describe how the folds in the horn are developed to fit into the cross-section of the box that needs to be built to hold it.

BP1Fanatic 12th August 2010 01:52 PM

Is the different panel colors an option...example: red for incorrect length & blue for correct length?

Brian Steele 12th August 2010 02:59 PM

1 Attachment(s)
Quote:

Originally Posted by BP1Fanatic (http://www.diyaudio.com/forums/subwoofers/171747-spreadsheet-folded-horn-layouts-post2270485.html#post2270485)
Is the different panel colors an option...example: red for incorrect length & blue for correct length?

I've attached an updated version of the spreadsheet that does this. When the graph is red, the panel dimensions have not been optimized. When optimized, the graph turns blue.

BP1Fanatic 12th August 2010 05:30 PM

Nice!!! How about swapping the locations of the Horn Expansion and Cross-Section charts for us blind folks?

BP1Fanatic 12th August 2010 06:11 PM

How was I able to obtain a 132.82L blue enclosure when my inputs are for a 210L enclosure?

http://dingo.care2.com/pictures/c2c/.../5/9529744.jpg

http://dingo.care2.com/pictures/c2c/.../5/9529747.jpg

L = 274.32 108.00 balance = 0.00
S1 = 516.13 L-check = 172.2
hmin = 6.42 L'-check = 167.8
S4 = 1032.26 dL = 4.4
hmax = 12.84 2.5%
p = 1.91 0.75
d = 40.64 16.00 17.50
h = 40.64 16.00 17.50
w = 80.42 31.66 33.16
delta = 0.02

Vol (1) = 212.38 l. 7.50 cu.ft.
Vol (2) = 166.42 l. 5.88 cu.ft.

http://dingo.care2.com/pictures/c2c/.../5/9529753.jpg

Brian Steele 12th August 2010 06:32 PM

Quote:

Originally Posted by BP1Fanatic (http://www.diyaudio.com/forums/subwoofers/171747-spreadsheet-folded-horn-layouts-post2270709.html#post2270709)
How was I able to obtain a 132.82L blue enclosure when my inputs are for a 210L enclosure?

From your images, it looks like you haven't optimized L. Your horn's length should be 274.3 cm, based on the HornResp input screen. However the value for L-check in your image is much less than 274.3 cm. Another sign that something's wrong is that the net volume (Vol 1) is more than the gross volume (Vol 2).

It looks like you have to complete steps 4 and 6 about three times to get the correct results (the chart plotting component that swaps the colours in the graph only checks the "balance" figure, not the "L-check" figure).

soho54 12th August 2010 08:16 PM

Quote:

Originally Posted by Brian Steele (http://www.diyaudio.com/forums/subwoofers/171747-spreadsheet-folded-horn-layouts-post2270080.html#post2270080)
One issue that's come up is calculated horn length.

I used the "centerline" method to determine horn length.

When you say "centerline" do you mean right angles through the corners? If so, this will always be a little long, and the horn will play shorter.

I haven't looked at your sheet yet. Is it unlocked?

You will have better luck if you can get the program to use SQRT(Inside path*Outside path) as the length of each section. This is the easiest way to get the average path length.


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