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12th August 2010, 08:57 PM  #21  
diyAudio Member
Join Date: Nov 2005
Location: Georgia

Quote:


12th August 2010, 09:03 PM  #22 
diyAudio Member
Join Date: Nov 2005
Location: Georgia

Ok, I'll see what I can do.
Can you verify the accuracy of this sketchup model to your finished build? Also the exact distance from the edge to the drivers center, or mounting edge lip to the throat end if you have it. Mouth to driver hole cutout with correct cutout size will work too. Also any bracing that you might have added. I don't see any in the pics, but I thought I remember you saying something about it. Maybe not. 
12th August 2010, 09:30 PM  #23  
diyAudio Member
Join Date: Nov 2007

Quote:
The driver's center is located 20 cm down the sloping portion. The driver is topmounted through the panel. The bracing didn't make any difference to the measured impedance minimum, so I suggest not bothering to include it in the model. 

12th August 2010, 09:44 PM  #24  
Mark Kravchenko  www.kravchenkoaudio.com
diyAudio Member

Quote:
Now that would be a truly awesome program. Can't begin to explain how much time I take folding horn designs into the smallest space. Quote:
I find AkaBak on the arcane side of intuitive. It was and is a great program. And for what it can do it is still quite powerfull. It's just that Hornresp is much easier to work with. Mark
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Mark 

12th August 2010, 11:19 PM  #25 
diyAudio Member
Join Date: Apr 2007

HornRes v28 now does parabolics, no need to specify conics. The error is small, but the reported volume in the schematic window is much more
accurate. Now, if we could only get more segments.
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Don Last edited by Don Snyder; 12th August 2010 at 11:25 PM. 
13th August 2010, 03:02 AM  #26 
diyAudio Member
Join Date: Nov 2007

It looks like the best correlation between predicted and measured results occurs when the path length through the folds is somewhere between the centerline method (Lc) and the centerline/arc method (Lca).
I also found a small bug in the spreadsheet's calculation of L. I will deal with that shortly. In the interim, I modified the graph to show the centerline of the path (dotted red line), the longest lenth (in black) and the shortest length (in green). For the TH I built: Centerline method gives 242.2 cm (dotted red line in the graph) Centerline method with arcs gives 225.6 cm (not illustrated) Sqrt method gives 241.4 cm (long length in black, short length in green) Measurement of the build TH suggests that L is somewhere around 233 cm. (The 0.7 method is going to give a value for L that's longer than the centerline method, which actual measurement suggests is too long, so I did not consider it in this exercise) It looks like the geometric mean between the centerline method and the centerline/arc method gives the closest approximation to the measured results, so I'm going to redesign the spreadsheet either around this or the centerline/arc method (for a bass horn, I think perhaps it might be best to err on the side of the horn being slightly too long rather than the horn being slightly too short). 
13th August 2010, 03:23 AM  #27 
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Join Date: Nov 2005
Location: Georgia

Brian Steele,
I have a preliminary AkAbak model set up. The first thing I noticed is that the HR model posted here is a bit different than the base numbers from the Excel sheet from there. I'll look into it more later. This is just a starter model with the extra mass and resistance of the bends not included, the path length has just been approximated. The next step would be to remove the corner sections and replace them with Acoumass/resistance components to take the edges off the peaks and displacement. Here is a pic of the AkAbak model on the left, and the original HR sim on the right. System 'DEMO1' Def_Driver 'Driver' dD=26cm dD1=11cm tD1=6.5cm Cone t1=1.1cm fs=39Hz Vas=92L Qms=7.5 Qes=0.31 Re=5.2ohm Le=0.37mH ExpoLe=0.618 Def_Const { S1 = 4.8e2; S2 = 6.3e2; S3 = 8.2e2; S4 = 9.6e2; S5 = 10.9e2; S6 = 10.1e2; S7 = 10.1e2; S8 = 11.8e2; S9 = 13.1e2; S10 = 12.1e2; S11 = 12.1e2; S12 = 14.5e2; S13 = 17.1e2; S14 = 16.1e2; S15 = 17.3e2; S16 = 15.8e2; S17 = 13.6e2; S18 = 13.6e2; S19 = 14.8e2; S20 = 13.4e2; S21 = 11.8e2; S22 = 13.6e2; S23 = 16.3e2; S24 = 15.3e2; S25 = 16.3e2; S26 = 17.7e2; L1 = 20e2; L2 = 26.7e2; L3 = 2.5e2; L4 = 3.3e2; L5 = 2.0e2; L6 = 33.0e2; L7 = 3.0e2; L8 = 3.9e2; L9 = 2.5e2; L10 = 30.5e2; L11 = 4.0e2; L12 = 5.2e2; L13 = 3.7e2; L14 = 4.0e2; L15 = 5.4e2; L16 = 4.0e2; L17 = 17.0e2; L18 = 3.0e2; L19 = 4.7e2; L20 = 4.0e2; L21 = 4.2e2; L22 = 4.8e2; L23 = 3.4e2; L24 = 13.9e2; L25 = 20.9e2; } Driver Def='Driver''Driver' Node=1=0=100=3 Waveguide 'Horn segment 1' Node=3=2 WTh=41.4cm HTh={S1} WMo=41.4cm HMo={S2} Len={L1} Waveguide 'Horn segment 2' Node=3=4 WTh=41.4cm HTh={S2} WMo=41.4cm HMo={S3} Len={L2} Waveguide 'Horn segment 3' Node=4=5 WTh=41.4cm HTh={S3} WMo=41.4cm HMo={S4} Len={L3} Waveguide 'Horn segment 4' Node=5=6 WTh=41.4cm HTh={S4} WMo=41.4cm HMo={S5} Len={L4} Waveguide 'Horn segment 5' Node=7=6 WTh=41.4cm HTh={S6} WMo=41.4cm HMo={S5} Len={L5} Duct 'Duct segment 6' Node=7=8 WD=41.4cm HD={S6} Len={L6} Waveguide 'Horn segment 7' Node=8=9 WTh=41.4cm HTh={S7} WMo=41.4cm HMo={S8} Len={L7} Waveguide 'Horn segment 8' Node=9=10 WTh=41.4cm HTh={S8} WMo=41.4cm HMo={S9} Len={L8} Waveguide 'Horn segment 9' Node=11=10 WTh=41.4cm HTh={S10} WMo=41.4cm HMo={S9} Len={L9} Duct 'Duct segment 10' Node=11=12 WD=41.4cm HD={S10} Len={L10} Waveguide 'Horn segment 11' Node=12=13 WTh=41.4cm HTh={S11} WMo=41.4cm HMo={S12} Len={L11} Waveguide 'Horn segment 12' Node=13=14 WTh=41.4cm HTh={S12} WMo=41.4cm HMo={S13} Len={L12} Waveguide 'Horn segment 13' Node=15=14 WTh=41.4cm HTh={S14} WMo=41.4cm HMo={S13} Len={L13} Waveguide 'Horn segment 14' Node=15=16 WTh=41.4cm HTh={S14} WMo=41.4cm HMo={S15} Len={L14} Waveguide 'Horn segment 15' Node=17=16 WTh=41.4cm HTh={S16} WMo=41.4cm HMo={S15} Len={L15} Waveguide 'Horn segment 16' Node=18=17 WTh=41.4cm HTh={S17} WMo=41.4cm HMo={S16} Len={L16} Duct 'Duct segment 17' Node=18=19 WD=41.4cm HD={S17} Len={L17} Waveguide 'Horn segment 18' Node=19=20 WTh=41.4cm HTh={S18} WMo=41.4cm HMo={S19} Len={L18} Waveguide 'Horn segment 19' Node=21=20 WTh=41.4cm HTh={S20} WMo=41.4cm HMo={S19} Len={L19} Waveguide 'Horn segment 20' Node=21=22 WTh=41.4cm HTh={S21} WMo=41.4cm HMo={S20} Len={L20} Waveguide 'Horn segment 21' Node=22=23 WTh=41.4cm HTh={S21} WMo=41.4cm HMo={S22} Len={L21} Waveguide 'Horn segment 22' Node=23=24 WTh=41.4cm HTh={S22} WMo=41.4cm HMo={S23} Len={L22} Waveguide 'Horn segment 23' Node=25=24 WTh=41.4cm HTh={S24} WMo=41.4cm HMo={S23} Len={L23} Waveguide 'Horn segment 24' Node=25=26 WTh=41.4cm HTh={S24} WMo=41.4cm HMo={S25} Len={L24} Waveguide 'Horn segment 25' Node=26=27 WTh=41.4cm HTh={S25} WMo=41.4cm HMo={S26} Len={L25} Duct 'Du1' Node=100=26 WD=41.4cm HD=30cm Len=1.7cm Radiator 'Horn mouth' Def='Horn segment 25' Node=27 Last edited by soho54; 13th August 2010 at 03:34 AM. 
13th August 2010, 03:31 AM  #28 
diyAudio Member
Join Date: Nov 2005
Location: Georgia

The above was with a 229.6cm path length.

13th August 2010, 03:42 AM  #29 
diyAudio Member
Join Date: Nov 2005
Location: Georgia

I will need the temp where you were at the time you took the measurement, and altitude as well to see what a difference it will make.

13th August 2010, 03:45 AM  #30  
diyAudio Member
Join Date: Nov 2007

Quote:
Good stuff. The Akabak impedance plot is a closer match to what I've actually measured. The resonance frequency is almost an exact match. As I mentioned in my previous message, the spreadsheet has a bug wrt calculation of the horn length. 

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