While the results often aren't perfect, DIY'ers like to experiment with this kind of stuff. we can't help ourselves!!!
By offering the WG and plug I think you are doing a good thing. Lots of very interesting designs will pop up. Not necessarily better , or even as good, but interesting, and who knows? better in some ways?
Mark
No, the HOM get lower in frequency with a wider coverage pattern, but a larger device is only good. Good that is up to a point of diminishing returns. An 18" waveguide may not be perceptably better than a 15" - I just don't know. I do know that costs, etc. go way up with size. You can see this in my pricing. An 18" would have to be around $500 each for me to even consider doing it.
Bigger mouth roundings appears to be a double edged sword. As the mouth gets rounder the waveguide is, in essence, getting shorter- not a good thing.
The stereoliths that we did was about a year ago. I don't know the process, it was in Thailand, and still it was expensive. Here, in that size, well all I can say is that I'm glad I'm not paying for it.
Bigger mouth roundings appears to be a double edged sword. As the mouth gets rounder the waveguide is, in essence, getting shorter- not a good thing.
The stereoliths that we did was about a year ago. I don't know the process, it was in Thailand, and still it was expensive. Here, in that size, well all I can say is that I'm glad I'm not paying for it.
Yes, well, 18" waveguides are going to be expensive regardless of how they are made. The point of the exercise is to question how many would need to be made using fiberglass and associated tooling before the unit cost would be less than creating one using stereolithography. Of course, that all presumes that a waveguide made from something like this would be usable in the first place.
I love this place
What? You start a party and send no invitations?
Josh, thanks for the revision.
Looking into Josh's latest worksheet, OS WG2, I find a very minor adjustment to be made. Cell C10 contains the throat exit angle for the CD. All is good.
Cell D10 contains the formula which converts the throat angle to radians for further digestion in the worksheet. The formula in D10 is flawed as it contains a hard value of "6" for the throat angle. Changing to a different entry value in cell C10 produces no change in output.
The fix is simple. Select cell D10 and in the fx box above, enter "D10" after the = sign in place of the "6". This makes the worksheet respond to changes in user input for throat angle.
I found this when I changed the value to 6.5 degrees and saw no change in the output. 6.5 is the angle most recently referred to by Earl for the DE250. With other devices YMMV.
Xc is the axis intercept for the point on the OS profile that is tangent to the throat angle.
Yc should be radius at that point &
a1 is the radius of the OS profile where it is parallel to the axis of the throat
Now, with this one should be able to enter a variety of throat radii and view changes in the profile. I have found this doesn't occur. More investigation is necessary into that part of the worksheet.
What? You start a party and send no invitations?
Josh, thanks for the revision.
Looking into Josh's latest worksheet, OS WG2, I find a very minor adjustment to be made. Cell C10 contains the throat exit angle for the CD. All is good.
Cell D10 contains the formula which converts the throat angle to radians for further digestion in the worksheet. The formula in D10 is flawed as it contains a hard value of "6" for the throat angle. Changing to a different entry value in cell C10 produces no change in output.
The fix is simple. Select cell D10 and in the fx box above, enter "D10" after the = sign in place of the "6". This makes the worksheet respond to changes in user input for throat angle.
I found this when I changed the value to 6.5 degrees and saw no change in the output. 6.5 is the angle most recently referred to by Earl for the DE250. With other devices YMMV.
Xc is the axis intercept for the point on the OS profile that is tangent to the throat angle.
Yc should be radius at that point &
a1 is the radius of the OS profile where it is parallel to the axis of the throat
Now, with this one should be able to enter a variety of throat radii and view changes in the profile. I have found this doesn't occur. More investigation is necessary into that part of the worksheet.
That's always the business decision, which is why I would not be one to enter into the 18" realm since I would doubt that one could make any money at it. A large initial investment that has to be amortized over the volume. Unless there is a sufficient volume this will make each piece quite expensive. And the only way that you would know for sure if that material would work is to try it. Gueni (sp?) pigs anyone? I'd love to know, but I wouldn't bet on it.
The second change
Looking further into the OS WG 2 worksheet, another small change is necessary.
Select cell C14. In the function box above, type in "=C3" and delete all other entries. This will make the calculated profile conform to user input in cell C3.
Has anyone experienced other unexpected behavior in the worksheet?
Looking further into the OS WG 2 worksheet, another small change is necessary.
Select cell C14. In the function box above, type in "=C3" and delete all other entries. This will make the calculated profile conform to user input in cell C3.
Has anyone experienced other unexpected behavior in the worksheet?
A requested change
Earl,
Would you be so kind as to suggest an appropriate range to which the OS WG2 worksheet should be expanded in order to accommodate a 15" waveguide?
The current one was sized to fit on an 8 1/2 x 11 sheet of paper and is obviously too small.
Following that, I'm going to solicit the help of any excel guru to remind me how to change the parameters of the profile and chart for printing. I only did it once a long time ago...any help would be appreciated.
Earl,
Would you be so kind as to suggest an appropriate range to which the OS WG2 worksheet should be expanded in order to accommodate a 15" waveguide?
The current one was sized to fit on an 8 1/2 x 11 sheet of paper and is obviously too small.
Following that, I'm going to solicit the help of any excel guru to remind me how to change the parameters of the profile and chart for printing. I only did it once a long time ago...any help would be appreciated.
I don't follow the question and I'm no Excel guru.
The wavguide is 7.5" high so it will be about 7.5" deep You should be able to do this to scale on 8.5 x 11. But be forwarned, few printers can print "to scale". Even if they say they do. I don't have one that will. I have to pre-distort the plot to get it to print to scale.
The wavguide is 7.5" high so it will be about 7.5" deep You should be able to do this to scale on 8.5 x 11. But be forwarned, few printers can print "to scale". Even if they say they do. I don't have one that will. I have to pre-distort the plot to get it to print to scale.
DIY Horn construction...crazy ideas I saw on the web #1
1) Print out horn contour and transfer-cut into plastic/aluminum to use as a plaster knife
2) borrow/build potter's wheel and using some core styro-foam under plaster, slop together a rough horn shape plaster
3) use plaster knife and measuring tools to create accurate horn model... after plaster hardens, fill any holes and smooth sand to match curve, then primer paint
4) coat hardened plaster horn with mold release and put into a 4-sided wooden box which will fit into your cabinet volume, and fill with excess amount of slow expansion urethane foam(polyurethane isocyanate). The rear board can have long screws that extend into the urethane as well as mounting holes for the compression driver.
5) remove plaster mold and soap-water wash off mold release grease, patch up any urethane blips
6) spray paint inside of urethane horn.
7) mount compression driver
1) Print out horn contour and transfer-cut into plastic/aluminum to use as a plaster knife
2) borrow/build potter's wheel and using some core styro-foam under plaster, slop together a rough horn shape plaster
3) use plaster knife and measuring tools to create accurate horn model... after plaster hardens, fill any holes and smooth sand to match curve, then primer paint
4) coat hardened plaster horn with mold release and put into a 4-sided wooden box which will fit into your cabinet volume, and fill with excess amount of slow expansion urethane foam(polyurethane isocyanate). The rear board can have long screws that extend into the urethane as well as mounting holes for the compression driver.
5) remove plaster mold and soap-water wash off mold release grease, patch up any urethane blips
6) spray paint inside of urethane horn.
7) mount compression driver
LineSource said:
Good luck! Been there, done that, gave up. The urethane foam expands with enough force to lift 200 lbs or more and will pull apart any box that you try to place around it. With a steel mold it might be possible, but even then I doubt it. The inner surface will be anything but smooth, unless it is under a lot of pressure. I had so much trouble with the expanding foams that I simply gave up on them.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.