Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

3D Modeling Tips and Tricks
3D Modeling Tips and Tricks
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 7th September 2015, 12:29 PM   #1
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Default 3D Modeling Tips and Tricks

I've been building a ton of loudspeakers and waveguides in 3D, and thought it might be worthwhile to post some of the shortcuts I've figured out.

It took me a while to figure out how to quickly make some of these shapes, so maybe this will save people some time.

First, here is how I print:

1) I use Autodesk 123D Design to model the speakers ($0)
2) I use Repetier and Slic3r to 'cut up' the model into something that can be printed ($0)
3) I use a Printrbot Simple Metal to print the designs ($599)

It is true that you can have things printed by Shapeways. I prefer printing it myself because you can get results in about twelve hours instead of a few days. And filament is so cheap, I can print a nice waveguide for about five bucks.
  Reply With Quote
Old 7th September 2015, 01:07 PM   #2
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Object one : an elliptical waveguide

Click the image to open in full size.
The first step in making an elliptical waveguide is to draw an ellipse. In this case, I am using the golden ratio. The ellipse has a width of 12.7mm and a height of 20.5mm. When we're finished this will give us a 1" wide entrance to the waveguide.

Click the image to open in full size.
Step two is to make the waveguide walls. I'm making a progressive transition waveguide. According to JBL, "Progressive Transition waveguides are unique because a single mathematically-continuous surface defines the waveguide from transducer- throat to waveguide-mouth. The distinctive feature is the lack of a traditional diffraction slot. Instead the sidewalls transition smoothly from the driver throat through to the square or rectangular mounting flange."

Translated into English, what we have is a curve that slooooooooowly transitions from the angle at the entrance (90 degrees) to the angle at the exit (180 degrees.)

Click the image to open in full size.
here's the real deal, for comparison

Note that we're not limited to an entrance of 90 and an exit of 180. We can use any angle we want. For instance, if you were using a compression driver instead of a dome, you might use a narrower entrance angle. IE, if your compression driver had an exit of twelve degrees, you could match the exit angle of the compression driver to the entrance angle of the waveguide to reduce diffraction.

The angle that you'll get in your waveguide is determined by the tangent on that circle that I cut out there. Again, I picked 45 degrees, because it works for me. You could pick any angle you want.

Click the image to open in full size.
Once we have that curve, we need to 'scale it up' to whatever size we want in the real world. In my case, I wanted a baffle width of 8". That means that I have to scale up the width of that curve to 3.5". (3.5" for the waveguide walls, times two, plus the width of the entrance, gives us 8" total.)

Once the curve is scaled up to size, we move the curve so it's adjacent to our ellipse that we made in step one.

Click the image to open in full size.
Then we "sweep" the waveguide wall around the ellipse. Basically the "sweep" tool lets us take one shape (the wall) and "sweep" it around another shape (the ellipse, which will be our throat.)

Click the image to open in full size.
Click the image to open in full size.
The last step in making the waveguide is to 'squash' one dimension. Basically we take the whole waveguide and squash it down to 61.7% of it's original dimension. What this does is it gives us a nice elliptical mouth, with a golden ratio of height to width. This isn't just for cosmetics; it improves the frequency response by reducing the on-axis 'hole' that you get with a round waveguide. (A round waveguide has a dip on axis, due to everything being equidistant from the throat; by making the waveguide elliptical we fix that.)

A couple of other advantages of an elliptical waveguide is that it allows for tighter spacing between the midrange and tweeter, which improves the vertical polars. And studies from Harman indicate that people prefer wide horizontal directivity and narrow vertical directivity. (I should really provide a citation for that, but I can't find it right now.)

Last edited by Patrick Bateman; 7th September 2015 at 01:16 PM.
  Reply With Quote
Old 7th September 2015, 01:27 PM   #3
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Click the image to open in full size.
elliptical cutouts are difficult to cut, so here's how to make a baffle. First, we make a rectangular solid. Then we 'snap' the waveguide to the rectangular solid. Using the 'snap' tool is fast way to line up a couple of shapes; it's way more accurate and easy than trying to do it with a mouse. Once they're 'snapped' together, we use the 'ungroup' tool to unglue them from each other.

Click the image to open in full size.
Then we merge the two shapes on top of each other. I've made an extra copy of both shapes because I'll need the copy in a minute...

Click the image to open in full size.
In this pic, I've 'subtracted' the waveguide shape from the rectangular solid. This gives me an inverse copy of the waveguide, basically a solid that's comprised of the empty space inside of the waveguide. In the pic, you can see how perfectly smooooooth the transition is from the throat to the mouth.

Click the image to open in full size.
Click the image to open in full size.
Then I use that inverted shape from the last step to 'slice' a shape out of the rectangular solid. I wind up with a baffled waveguide that's 200mm x 129mm x 36mm, or 7.87" x 5.07" x 1.4"

These dimensions are just about perfect for a nice two way with a 7" woofer. The waveguide will control directivity down to 1687hz, where you can 'hand off' to the woofer. The depth of the waveguide will give us a bit of horn loading down to around 2700hz. (Check with hornresp to get the exact figure.) If you wanted to load the tweeter lower, just use a deeper waveguide.
  Reply With Quote
Old 7th September 2015, 02:28 PM   #4
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Object Two : A Lecleach Horn

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Here's a LeCleach horn, built using the same methods as the waveguide from the original post in the thread. To get the curve, I modeled the loudspeaker in Hornresp, then used the 'export' function to generate the width of each step in the LeCleach curve.

For me, the easiest way to plot the curve in 123D was to use the 'Polyline' tool. The Polyline tool lets you input an angle for your line. And Hornresp lists that angle when you export the horn curve. So you just take the number from Hornresp and plug it into 123D.
  Reply With Quote
Old 7th September 2015, 03:52 PM   #5
xrk971 is online now xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
3D Modeling Tips and Tricks
Nice work! Can you please share the STL files?
Thanks
  Reply With Quote
Old 1st January 2018, 11:30 PM   #6
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Quote:
Originally Posted by xrk971 View Post
Nice work! Can you please share the STL files?
Thanks
I need to set up a file sharing site, I don't have an easy to share anything at the moment.
  Reply With Quote
Old 1st January 2018, 11:50 PM   #7
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
I've really become a fan of diffraction horns lately. I do a lot of Synergy Horns, and a diffraction slot really simplifies a Synergy Horn. Here's why:

The way that a horn or a waveguide works is that it 'concentrates' the output of the driver into a narrower beam. For instance, a dome tweeter on a baffle might be able to generate 90dB at 2khz on a flat baffle, but if you put it on a 90 degree waveguide, the output will go up to as high as 100, even 102dB

So... What does this have to do with Synergy Horns?

I'd argue that the hardest part about building a Synergy Horn is getting the stupid tweeter to reach low enough to 'hand off' to the midranges. I can't even count the number of Synergy Horns that I've had to toss into the trash because the tweeter 'ran out of steam' and couldn't dig deep enough to 'meet up' with the midrange.

This isn't a problem for conventional two ways, because in a conventional two way it's pretty trivial to raise the xover point on the midrange to accomodate the tweeter. But in a Synergy Horn, it's a HUGE issue, because both the mids and the tweeter are horn-loaded. Due to that, the maximum we can run the mids can be as little as 1200-1500Hz. It places a huge demand on the tweeter, which is probably one of the reason that the Danley Genesis horns use a complex device to 'sum' multiple tweeters, and many of the Danley Synergy Horns use coaxial compression drivers that cost about $1000 per pair.

So...

A diffraction slot solves a lot of these issues. Basically lets us have our cake and eat it too. It allows us to have a waveguide with a specific pattern, like 90 x 60, along with the 'gain' of a horn. (Because the diffraction slot adds about 1-2" to the depth of the horn, it loads everything on the horn to a lower frequency, the tweeter in particular.) Best of all, that diffraction slot gives us a mighty convenient spot to mount some midranges to the horn.

I'm really becoming a fan.

Anyways, enough of my proselytizing, here's how to make one.

Click the image to open in full size.
18Sound XT1086 is the finest diffraction horn I've measured. They put a lot of effort into reducing diffraction at the edge of the diffraction slot; you wouldn't even know it was there if you didn't look closely. I've made some attempts to copy the JBL M2 diffraction horn, and the 18Sound performs better than any JBL M2 clones I've made. It's a simple elegant design.

Click the image to open in full size.

Click the image to open in full size.
To make it, follow the same recipe in this thread that's for asymmetrical waveguides. The 'catch' is that we're making TWO asymmetrical waveguides, and we're bonding the two together.

The first piece is the diffraction slot. That slot is an asymmetrical waveguide with 40 degrees of vertical coverage and 13 degrees of horizontal coverage. And then the SECOND waveguide has 90 degrees of horizontal coverage, and 55 degrees of vertical.

The net effect is that you wind up with a waveguide that has an average coverage of 72.5 degrees, 90 degrees of horizontal coverage, 55 degrees of vertical coverage. Just like any conventional waveguide. The addition of the diffraction slot makes the overall device 1.5" deeper.

This additional depth makes a MASSIVE DIFFERENCE in loading the tweeter. Here's an example:

The 18Sound XT1086 is 5" deep. That will load the tweeter down to approximately 675Hz. (speed of sound / 5" / 4)

Now if you were to remove the diffraction slot, the depth of the waveguide would drop to 3.5" deep. That would load the tweeter to just 964hz.

That probably doesn't sound like a big difference, we're talking about half an octave. But it's coming RIGHT at a point where we need all the gain that we can get when we're building a Synergy Horn. Output from the midranges is rarely a problem, but output from the tweeter is a huge issue, and that additional depth can give us as much as 10dB more output at 1000Hz. This REALLY simplifies the crossover from midrange to tweeter in a Synergy Horn.

Click the image to open in full size.
In this side view, I've sliced the waveguide in half, illustrating the vertical coverage of the waveguide. Note the transition is fairly smooth, to reduce diffraction. I could make it a lot smoother with a 'smoothing' function, but that would obscure how I built the waveguide, which is the point of this thread.

Click the image to open in full size.
In this vertical cutaway, the diffraction slot is more apparent.

Click the image to open in full size.

Click the image to open in full size.

The finished diffraction horn

Click the image to open in full size.
Another pic of the 18Sound for comparison's sake
  Reply With Quote
Old 15th July 2018, 07:20 PM   #8
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
In a discussion on Facebook, someone asked me to share my T/S params that I use for modeling high frequency waveguides in Hornresp.

To be honest, though I've designed a LOT of waveguides, I generally don't model the waveguides in Hornresp. The reason is because waveguides are fairly predictable in my experience. The process of making a waveguide is simple:

1) determine the vertical beamwidth

2) determine the horizontal beamwidth

3) determine whether you want a circular or rectangular mouth

4) pick a profile (conical, oblate spheroidal, tractrix, spherical, etc)

5) Match the exit angle of the compression driver to the entrance angle of the waveguide

6) Add an appropriate roundover at the mouth

And you're done! I don't see any real need to model it in hornresp because what would that accomplish? I know that the depth of the waveguide needs to be sufficient to load the driver down to about an octave below the xover frequency, but I can do that math in my head. (speed of sound / depth of waveguide / 4)

Occasionally I'll fire up axidriver to run a sim; axidriver can show you the polar response and the frequency response of a horn. But generally I only do that if I'm including some type of phase plug in the waveguide design. And even in THAT case, I'll frequently just design, build and print the phase plug without simulating it. (You can design a phase plug in about 30 minutes.)
  Reply With Quote
Old 14th March 2019, 12:45 AM   #9
philpope is offline philpope  United Kingdom
diyAudio Member
 
Join Date: Jul 2007
Default diffraction slot throat distortion

Quote:
Originally Posted by Patrick Bateman View Post
I've really become a fan of diffraction horns lately. I do a lot of Synergy Horns, and a diffraction slot really simplifies a Synergy Horn. Here's why:

The way that a horn or a waveguide works is that it 'concentrates' the output of the driver into a narrower beam. For instance, a dome tweeter on a baffle might be able to generate 90dB at 2khz on a flat baffle, but if you put it on a 90 degree waveguide, the output will go up to as high as 100, even 102dB

So... What does this have to do with Synergy Horns?

I'd argue that the hardest part about building a Synergy Horn is getting the stupid tweeter to reach low enough to 'hand off' to the midranges. I can't even count the number of Synergy Horns that I've had to toss into the trash because the tweeter 'ran out of steam' and couldn't dig deep enough to 'meet up' with the midrange.

This isn't a problem for conventional two ways, because in a conventional two way it's pretty trivial to raise the xover point on the midrange to accomodate the tweeter. But in a Synergy Horn, it's a HUGE issue, because both the mids and the tweeter are horn-loaded. Due to that, the maximum we can run the mids can be as little as 1200-1500Hz. It places a huge demand on the tweeter, which is probably one of the reason that the Danley Genesis horns use a complex device to 'sum' multiple tweeters, and many of the Danley Synergy Horns use coaxial compression drivers that cost about $1000 per pair.

So...

A diffraction slot solves a lot of these issues. Basically lets us have our cake and eat it too. It allows us to have a waveguide with a specific pattern, like 90 x 60, along with the 'gain' of a horn. (Because the diffraction slot adds about 1-2" to the depth of the horn, it loads everything on the horn to a lower frequency, the tweeter in particular.) Best of all, that diffraction slot gives us a mighty convenient spot to mount some midranges to the horn.

I'm really becoming a fan.

Anyways, enough of my proselytizing, here's how to make one.

Click the image to open in full size.
18Sound XT1086 is the finest diffraction horn I've measured. They put a lot of effort into reducing diffraction at the edge of the diffraction slot; you wouldn't even know it was there if you didn't look closely. I've made some attempts to copy the JBL M2 diffraction horn, and the 18Sound performs better than any JBL M2 clones I've made. It's a simple elegant design.

Click the image to open in full size.

Click the image to open in full size.
To make it, follow the same recipe in this thread that's for asymmetrical waveguides. The 'catch' is that we're making TWO asymmetrical waveguides, and we're bonding the two together.

The first piece is the diffraction slot. That slot is an asymmetrical waveguide with 40 degrees of vertical coverage and 13 degrees of horizontal coverage. And then the SECOND waveguide has 90 degrees of horizontal coverage, and 55 degrees of vertical.

The net effect is that you wind up with a waveguide that has an average coverage of 72.5 degrees, 90 degrees of horizontal coverage, 55 degrees of vertical coverage. Just like any conventional waveguide. The addition of the diffraction slot makes the overall device 1.5" deeper.

This additional depth makes a MASSIVE DIFFERENCE in loading the tweeter. Here's an example:

The 18Sound XT1086 is 5" deep. That will load the tweeter down to approximately 675Hz. (speed of sound / 5" / 4)

Now if you were to remove the diffraction slot, the depth of the waveguide would drop to 3.5" deep. That would load the tweeter to just 964hz.

That probably doesn't sound like a big difference, we're talking about half an octave. But it's coming RIGHT at a point where we need all the gain that we can get when we're building a Synergy Horn. Output from the midranges is rarely a problem, but output from the tweeter is a huge issue, and that additional depth can give us as much as 10dB more output at 1000Hz. This REALLY simplifies the crossover from midrange to tweeter in a Synergy Horn.

Click the image to open in full size.
In this side view, I've sliced the waveguide in half, illustrating the vertical coverage of the waveguide. Note the transition is fairly smooth, to reduce diffraction. I could make it a lot smoother with a 'smoothing' function, but that would obscure how I built the waveguide, which is the point of this thread.

Click the image to open in full size.
In this vertical cutaway, the diffraction slot is more apparent.

Click the image to open in full size.

Click the image to open in full size.

The finished diffraction horn

Click the image to open in full size.
Another pic of the 18Sound for comparison's sake
using a difraction slot with a lower flare rate will hugely increase throat distortion due to adiabatic air compression. one of the main benefits of the synergy horn is that using a conical horn means a very high flare rate where the compression driver is mounted - allowing the compression driver to operate at full output without the usual distortion levels found with other horns.
  Reply With Quote
Old 14th March 2019, 01:35 AM   #10
Patrick Bateman is offline Patrick Bateman  United States
diyAudio Member
 
Patrick Bateman's Avatar
 
Join Date: Oct 2006
Location: San Diego
Quote:
Originally Posted by philpope View Post
using a difraction slot with a lower flare rate will hugely increase throat distortion due to adiabatic air compression. one of the main benefits of the synergy horn is that using a conical horn means a very high flare rate where the compression driver is mounted - allowing the compression driver to operate at full output without the usual distortion levels found with other horns.
True, but I still like diffraction slots.

They're useful if you're trying to 'have your cake and eat it too', basically allowing wide beamwidth while still loading the tweeter.

My waveguides are for home use and my midranges are two inches in diameter; throat distortion isn't a huge concern.
  Reply With Quote

Reply


3D Modeling Tips and TricksHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
How To Solder Tips and Tricks Eddiegnz1 Tubes / Valves 21 20th December 2013 09:52 AM
Tube Tips/Tricks for beginners SamK2012 Tubes / Valves 10 19th November 2012 12:12 PM
Breadboarding/Prototyping - How to and Tips/Tricks Steven-H Equipment & Tools 60 26th August 2010 02:37 PM
3D Modeling?? Nathan1k9 Multi-Way 18 10th January 2007 02:11 AM
Couple of tips/tricks peace brainerd Everything Else 0 10th April 2006 03:57 PM


New To Site? Need Help?

All times are GMT. The time now is 01:22 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki