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Another pi midhorn question. [message #46839] Sat, 07 May 2005 02:56 Go to next message
Kim Schultz is currently offline  Kim Schultz
Messages: 85
Registered: May 2009
Viscount
index.php?t=getfile&id=1473&private=0


Hi Wayne.

I wanted to make a cad drawing of the midhorn, to get the angles on the sides.

Just bought a new tablesaw, and want to try to minimize the sanding a bit, by cutting the angles on the saw.

But when I make the sides 14.5" long, the top and bottom becomes 11.37" long. And when I make the top and bottom 11" long, the sides become 14.21" long.

Which one is correct, can you tell me the exact depth of the horn, that way I can draw it up using depth instead.

I have included a picture of the two drawings.

Regards
Kim
  • Attachment: 7pi_horn.jpg
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Re: Another pi midhorn question. [message #46840 is a reply to message #46839] Sat, 07 May 2005 03:41 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

It also shifts a bit depending on the thickness of the wood. Make the throat cutout exactly 4.5" square. Make the sides 45° and the top and bottom 20°, and make the mouth 24" x 12".


Re: Another pi midhorn question. [message #46841 is a reply to message #46840] Sat, 07 May 2005 04:46 Go to previous messageGo to next message
Kim Schultz is currently offline  Kim Schultz
Messages: 85
Registered: May 2009
Viscount
Thx Wayne, I´ll go with the short version on the drawing and make the top and bottom 11" and the sides a bit shorter than 14.5".
That fits 20º and 45º best.

But don´t you have the depth of the horn, the only thing I can see could change is the mounting plate thickness, and not the horn itself.



Re: Another pi midhorn question. [message #46844 is a reply to message #46841] Sat, 07 May 2005 12:52 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

Overall, it's about eleven inches, depending on the thickness of the wood of the throat mount plate. Using a little trigonometry, you can find the length you're looking for using the formula length = cos45°(14.5"), about 0.707 times the length of the side 14.5", or approximately 10.25". If you use these figures, the mouth will actually be a little larger than 12" x 24", which is just fine.


Think I got it now :) [message #46845 is a reply to message #46844] Sat, 07 May 2005 15:42 Go to previous messageGo to next message
Kim Schultz is currently offline  Kim Schultz
Messages: 85
Registered: May 2009
Viscount
If you take cos45º(14.5") you get 10.25".
And if you take (10.25"/11)inv cos you get 21.28º

That gives a mouth of 12.5" x 25".

Using 11" as the top and bottom with 3/4" wood and 12" x 24" mouth, the depth is 11.09", that´s close enough, so this is how I´ll build them.

I´ll begin cutting wood on monday.

Regards
Kim

Re: Think I got it now :) [message #46846 is a reply to message #46845] Sat, 07 May 2005 16:00 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

You're exactly right.


Re: Another pi midhorn question. [message #46850 is a reply to message #46839] Mon, 09 May 2005 08:29 Go to previous messageGo to next message
GarMan is currently offline  GarMan
Messages: 960
Registered: May 2009
Illuminati (2nd Degree)
Kim,

When Wayne announced his midrange horns last year, I spent a good afternoon going through my old math books, trying to figure out the angles. You know what I ended up doing? Built a mock up with 1/4" MDF to measure the angles directly off of it. Only took an hour to do the mock up.

With a mock up, you don't even have to "measure". Just copy the angle to a sliding bevel and transfer to the saw.

Gar.

Re: Another pi midhorn question. [message #46855 is a reply to message #46850] Mon, 09 May 2005 15:54 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

When I was developing these horns, I made several versions with different throats and different mouth sizes. The last few models were only slightly different, and we really only different because we were deciding how to manufacture them and what cut angles to make. The biggest issue we had is with wood thickness. You need different cuts and jigs for each wood thickness.

The basic dimensions shown in the plans are simplified, and you'll need to setup cut dimensions and angles for your wood. We have three different jigs for different various wood sizes. The first horn is the hardest, and after that, they go pretty easy. That's why we make flat pack kits available, because we have the production issues nailed down. This makes it easier for DIY builders that aren't setup to do precise angles and what not.


Re: Another pi midhorn question. [message #46877 is a reply to message #46850] Fri, 13 May 2005 03:22 Go to previous messageGo to next message
Kim Schultz is currently offline  Kim Schultz
Messages: 85
Registered: May 2009
Viscount
I build a midhorn with 19mm MDF last monday, using 20º on the ends of the sides and 45º on the ends of the top and bottom.

I had converted it all to metric and made a drawing in cad, that ended up making to mouth 63,5cm x 30,5cm, and the depth without mouting plate 26cm.

Now I have a pretty good idea how to make it the next time.

Which will not be in a while, I have to install floor heating and a new kitchen in the house, before I can do some more wood cutting for speakers.

Re: Another pi midhorn question. [message #80125 is a reply to message #46840] Sat, 21 June 2014 13:45 Go to previous messageGo to previous message
Nelson Bass
Messages: 39
Registered: November 2012
Baron
I made a 3D model of the midrange horn in SolidWorks:

index.php?t=getfile&id=1474&private=0


I settled the angles at 90x40deg and the horn mouth width to 24".
That makes the mouth around 11.65" high not 12" and the inside depth is 9.75".

Good enough? Razz
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