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Multi-Way Conventional loudspeakers with crossovers

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Old 21st July 2019, 01:55 AM   #21
Patrick Bateman is offline Patrick Bateman  United States
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this step can be skipped if you don't care about a baffle.

But if you want a baffle, here's how to do it:

Click the image to open in full size.
Step 1, create a baffle and align it with the waveguide that you made

Click the image to open in full size.
I create three copies:

The first set of copies is the union of the baffle and the waveguide.

The second set is the wavguide MINUS the baffle.

The third set is the baffle MINUS the waveguide.

Click the image to open in full size.
And then I merge the three sets together to get this.
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Old 21st July 2019, 03:36 AM   #22
Patrick Bateman is offline Patrick Bateman  United States
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In post #21, the last post, I show how to add a baffle to the waveguide.

The exact same process is used to add an interface to the waveguide for the tweeter. In this case I'm going to add a 3.5" interface for the tweeter.

Click the image to open in full size.
This 3.5" disc will be added to the waveguide, for the tweeter.

Click the image to open in full size.
I make three copies of the set.

Click the image to open in full size.

Click the image to open in full size.

Just as last time, I do the following:

1) one set will become the intersection of the two solids

2) one set will become the tweeter interface subtracted from the waveguide

3) one set will become the waveguide subtracted from the tweeter interface

And then the three pieces will be merged together.



Click the image to open in full size.
Here's how it looks when finished

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

And here's the finished solid! All done.

Click the image to open in full size.

Here's a closeup of the throat. Note how it's absolutely perfect. No step, no discontinuity.

That's it! You can now make any waveguide you want with a 3D printer. And vertical angle, any horizontal angle, any throat diameter... Have at it.

Last edited by Patrick Bateman; 21st July 2019 at 03:40 AM.
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Old 21st July 2019, 04:56 AM   #23
Patrick Bateman is offline Patrick Bateman  United States
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Click the image to open in full size.

Click the image to open in full size.

Here's the predicted response curves of the waveguide, on the horizontal and vertical axis.

I'd say this is fairly great performance. I think that if the vertical angle was increased, it might improve the horizontal; note how the vertical polars are superior.
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Old 21st July 2019, 06:53 AM   #24
andy19191 is offline andy19191  Europe
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The most natural way to do this would appear to be to define all your geometry in the 3D CAD program you are using at the end, extract the boundary surface and pass it to your BEM solver as an STL file or a some other format that is accepted. Possibly via an intermediate mesh generator if the quality of the triangles in the STL file are insufficient. Presumably something about this approach doesn't work. Can I ask what?

Are you including the geometry of the tweeter and/or compression driver. If not, how confident are you that the absence will not be degrading the quality of the simulations at higher frequencies?

PS Perhaps I should add that I have more than a casual interest since I am currently developing a mesh generator in support of FEM and BEM simulations.
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Old 21st July 2019, 01:58 PM   #25
chrapladm is offline chrapladm  Australia
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This is all above my head but I am going to try and figure out how to build my TPL200 synergy horn. Have to try and figure out what the dimensions of the walls need to be for my wants and space and then build the thing and see how it sounds.

Just need to figure out how to start.
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Old 21st July 2019, 05:03 PM   #26
Patrick Bateman is offline Patrick Bateman  United States
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Quote:
Originally Posted by chrapladm View Post
This is all above my head but I am going to try and figure out how to build my TPL200 synergy horn. Have to try and figure out what the dimensions of the walls need to be for my wants and space and then build the thing and see how it sounds.

Just need to figure out how to start.
posts one through four of this thread describe that:

step 1: draw two circles. One circle is at the throat and one is at the mouth.

step 2: connect the two circles with a line that's tangent to both.

step 3: repeat steps one and two to define the *outer* wall of the waveguide. (Steps 1 and 2 define the inner wall.)

step 4: extrude that shape.

step 5: copy that piece from step 3, three times.

step 6: now you have the four walls of your waveguide. Arrange those pieces based on the diameter of your radiator.

If you want to get fancy, and you probably do, you can use different angels or the horizontal and vertical walls. The instructions described here will create a waveguide where the horizontal and vertical are identical.

Another trick that you can do, to get varying vertical and horizontal angles, is to arrange the pieces in a rectangle even though you need a square throat. For instance, if you need a square throat that measures one inch by one inch, but you make the throat 1.5" by 1", then you can "squash" the entire shape to make the vertical and horizontal asymmetrical. I like this trick a lot because this solution is way WAY easier than trying to figure out the correct angle to get the asymmetrical pieces to meet at the mouth.

If you do a google search on the forum I've posted these solutions scattered all over a few threads. I'm not the most organized person lol

site:diyaudio.com bateman 123D - Google Search

When you do this search, click on the "images" tab
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Old 21st July 2019, 05:17 PM   #27
Patrick Bateman is offline Patrick Bateman  United States
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Quote:
Originally Posted by andy19191 View Post
The most natural way to do this would appear to be to define all your geometry in the 3D CAD program you are using at the end, extract the boundary surface and pass it to your BEM solver as an STL file or a some other format that is accepted.
That's how we were doing things back in November of 2018. It's a valid way to go, but Mabat's software is a ZILLION times faster.

Here's how I did things in November 2018:

step 1: make a waveguide in 123D (6-24 hours)
step 2: turn the STL into a mesh (15 minutes)
step 3: The really exhausting part was defining all the parts of the mesh. I had to literally click on triangles, one by one, and define whether they were the waveguide, the radiator, the mouth, etc. (four hours)

I have BOXES of waveguides in my garage. Hundreds and hundreds of hours put into them. And mabat's software compresses this entire process into 15-30 minutes.

You can see that in this thread itself, for instance the horizontal polars on the waveguide that I posted yesterday are very good but not perfect. Mabat's software makes it easy to do those tiny little tweaks that would otherwise take 40-60 hours to do. Consider that five years ago we had to do this in WOOD. (shudder.)
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Old 21st July 2019, 05:22 PM   #28
Patrick Bateman is offline Patrick Bateman  United States
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I wrote this in the ath4 thread, and it applies here. Basically if we could figure out how to get meshmixer to simply "fill in" the waveguide it would simply using it in a 3D program, because you could use the shape as a "mold."

"
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Originally Posted by mabat View Post
That is great, Patrick (or John). The first step, i.e. converting STL to solid, can also be easily automated. I'll definitely do that, to generate the STL as solid right away, I just have been quite busy for the last several months so not much work has been done on ath4.
The crazy thing, is that I could SWEAR that I was able to get meshmixer to close that waveguide. Last month in meshmixer I used some combination of settings in meshmixer, and it simply "filled in" the inside of the waveguide.

For the life of me, I couldn't get it to do that yesterday.

It's not the end of the world; extruding the shape gets the job done too, but it's messier."

Last edited by Patrick Bateman; 21st July 2019 at 05:26 PM.
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Old 21st July 2019, 05:50 PM   #29
andy19191 is offline andy19191  Europe
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Quote:
Originally Posted by Patrick Bateman View Post
That's how we were doing things back in November of 2018. It's a valid way to go, but Mabat's software is a ZILLION times faster.

Here's how I did things in November 2018:

step 1: make a waveguide in 123D (6-24 hours)
step 2: turn the STL into a mesh (15 minutes)
step 3: The really exhausting part was defining all the parts of the mesh. I had to literally click on triangles, one by one, and define whether they were the waveguide, the radiator, the mouth, etc. (four hours)

I have BOXES of waveguides in my garage. Hundreds and hundreds of hours put into them. And mabat's software compresses this entire process into 15-30 minutes.

You can see that in this thread itself, for instance the horizontal polars on the waveguide that I posted yesterday are very good but not perfect. Mabat's software makes it easy to do those tiny little tweaks that would otherwise take 40-60 hours to do. Consider that five years ago we had to do this in WOOD. (shudder.)
Thanks for the post which gives me some idea of the way DIY speaker folk have been going about things and particularly the length of time they are prepared to put in without abandoning.

I shall add simulations of waveguides to the top of my todo list but it will follow after my current simulations of cabinet vibration which has grown larger than intended due to the software I intended to use proving unsuitable. It would seem to be a common problem.
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Old 21st July 2019, 06:04 PM   #30
Patrick Bateman is offline Patrick Bateman  United States
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Originally Posted by andy19191 View Post
Thanks for the post which gives me some idea of the way DIY speaker folk have been going about things and particularly the length of time they are prepared to put in without abandoning.
Ha, it's the one part that I really love about making loudspeakers. The reason that my current project (1) has stretched on forever is because I *really* hate crossovers

(1) "Unitized" Image Control Waveguide
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