Waveguides for 3D printers and CNC's

[Bear]

I still haven't gotten around to sending you my T25A. Let me know if you're still interested. That project is going to be a LONG way away.

[augerpro]

Yep, I'm still interested, thanks!

[scottvalentin]

Brandon, do you know if the OT19 guide would match up with an SB19 tweeter? I have 3 SB19s from an old project and am looking to repurpose them into new LCRs, and wondering if the waveguides for the OT19 could work.

Thanks

[augerpro]

I'm not sure. What is the diaphragm diameter at the outside of the surround? When you take the faceplate off is there a flat surface to attach to underneath?

[augerpro]

I've posted the files from the last round at my website

[augerpro]

Going forward I'm thinking about posting .3MF instead of .STL files. They have the units included so there is no confusion if the design is in inches or mm. Also this format apparently reduces the weird intersecting manifold problems that some printers' websites choke on when you upload a .stl file. Anyone see any issue with this? I think most slicers can handle .3MF just fine?

[augerpro]

Little teaser of some waveguides I'll be measuring this week:



I'll also be verifying the T25A works on the waveguides I did for the T25B. And the newest generation of Scanspeak waveguides where I hope to continue the improvement I made last time for the soft domes, which can be a real problem on waveguides.

[augerpro]

New waveguides! Bliesma T34B looks pretty good out of the gate. I think I've finally nailed the throat for the Scanspeak ring radiator, so I'll be expanding to other sizes and shapes now. The Scanspeak dome is a bit tougher nut to crack. But I'm going to move to a different contour, I suspect fabric domes work better in OS contours. Unfortunately, my Peerless DA25TX had a resonance at 16khz, must be defective. I have another on order.

[augerpro]

Refined a couple of the previous designs and measured them today. Also added the first variant for the Peerless DA25TX. I'm surprised by the Peerless, it's a small dome which has worked well for me, but this has a big dip on axis. I would have expected it to measure very close to the SB26ADC given how similar the domes are. I may have to start working in ATH/ABEC for this one to figure out what works.

[JonMarsh]

Just tossing my $0.02, I've never gotten a satisfactory (to me) waveguide setup working with the DA25, and have tried several approaches.

I think there are characteristics we/I don't yet fully understand (gross understatement) about how the the interface between a dome of a specific curvature with a specific size surround works with the immediate throat area of waveguides in the frequency range of 8-20kHz. That's always where I see the most "unexplained" or "unexpected" variation.

Note, what you're seeing with the T34B BlieSMa mirrors my own experience to an extent with the T34A; however, I'm using a different waveguide, maybe a bit less fall off, off axis out to 45 degrees. The very narrow surround is a GOOD THING in my opinion. As an example of why a wide surround is NOT a good thing,

But hey, I haven't been working this area much lately, still too busy trying to get settled with the relocation - that process will continue through the middle of next year, should close on the house in construction in March.

And I would redo this measurement after things get setup- but this gives an idea of the issues.






I rather prefer the results of a T34A with a cheap Visaton waveguide (148R)

[Bear]

I'll also be verifying the T25A works on the waveguides I did for the T25B.

Looking forward to this one.

[augerpro]

Here are some measurements of the Bliesma T25A, to see how it measures on the waveguides I made for the T25B. The domes are very different, the A version is much taller. Clearly there is an issue here, which is disappointing.

[elijahscott82]

I built a speaker with waveguide using a 45 degree chamfer bit with a 3/4"mdf outer box and .5" inside plywood waveguide. This was made for the peerless 1" corundum tweeter so 1.25" overall depth. The chamfer edges where softened by hand to blend it out smoother also. Initially testing the tweeter I would get a pretty bad drop at 9-10k with this type of waveguide and I started noticing after I would put on .5" or larger stickers on the front of the grill this would extend the response a bit. I was curious about trying these little feet on top of a bumper about .6" onto the front of the grill over the tweeter for a phase plug and it continued to extend the response from this pointed little foot I used. Im going to make some epoxy ones a little more elegant looking but I was surprised how much of a difference these added to my shape of waveguide.
These are little bumper feet I found at ace hardware just experimenting with a smaller extended pointed piece kind of like a ring radiator of sorts not thinking it would help at all but it really did a lot.
The blue graph is eq'd after the fact and works very well.
Green is response with those phase plugs I made without eq.

The tweeters mounting plate was cut down as much as I could to fit into my speaker. Its very close to the midrange and much better time aligned depth wise.

[elijahscott82]

some more pictures of the waveguide and speaker.

[elijahscott82]

how the throat looks up close to the mounting plate

[augerpro]

Thanks for sharing that! I did include the .25" phase shield as used in my SB26 waveguide and it didn't really do anything. I'll try experimenting with large ones like yours. Did the dot look good, or only when you added the cone?

[elijahscott82]

Thanks for sharing that! I did include the .25" phase shield as used in my SB26 waveguide and it didn't really do anything. I'll try experimenting with large ones like yours. Did the dot look good, or only when you added the cone?

The dots I tried where just little stickers. The smallest was .25” and it didn’t do much at all. .5” was the smallest that started making a change.
5/8th was the best I found. Extending out that size made the largest but even just the sticker at 5/8th made it a lot better but still dropped around 11-12000.

[elijahscott82]

Here’s some measurements of my new phase plug I made from epoxy. Little bigger and longer than the one I had before. Pretty massive difference between them all. No screen is green so basically falls off at 8000. First phase plug was good second is best. Very easy to eq this flat. Pretty surprised how much of a change even the one I made has made for my 45 degree wave guide. Has nobody else tried using different shapes phase plugs like this? All I see is people doing very small phase plugs in wave guides.
Green-no screen no phase plug
Purple-1st phase plug no eq
Orange - new longer/bigger phase plug no eq

The others are with eq and others without.

This is for the peerless da25 corundum tweeter

[augerpro]

Thanks for the info! I'll try some of these ideas for the Peerless. In the pic of three cones, which was the best performing without eq?

[elijahscott82]

Thanks for the info! I'll try some of these ideas for the Peerless. In the pic of three cones, which was the best performing without eq?

The newest larger ones I made from epoxy are the best. The two in the picture are identical. I attached them onto the grill with hot glue. They are the orange in the chart of the 3 without eq. They continue out without any help from eq straight on. The are slightly bigger Than the others and bigger on the bottom. Probably close to .75” at the bottom but I’ll measure the others I made to make sure.
In the chart with the 3 measurements they start to branch off at 5khz and up. The smaller one doesn’t have the push the larger one does but still is a big improvement over no phase plug. Without a phase plug is really bad in the wave guide I made. After 9khz it drops like a rock.
These are also measured about 40” away. No ir window limiting either
I have a 33uf cap on the tweeter and it’s a 6db slope in my dsp in the measurements.

[JonMarsh]

New designs! This round I improved the tweeter interface for the Scanspeak drivers and the results are much improved. I also designed new aspect ratio versions of the 6.5" Bliesma T25B waveguide to investigate a middle ground between my typical 1 : 0.618 aspect ratio and the circular waveguide I posted a couple months ago. I also did vertical measurements to shed light on some recent discussion on the response tradeoff between circular and elliptical mouths.

I'll get the new design files up on my website this week.

I liked the 1.81 aspect ratio result for the T25. That's looking pretty darn good!

[augerpro]

Here are two more variants of the T34B waveguides, and a new Scanspeak R2904/7000 waveguide. I'll be adding the T34B designs to my website in a few weeks.

[augerpro]

I'm making a test cabinet to do some research on edges before I start final designs on a family of speakers. This gave me a chance tonight to try my routing template. Worked as expected, so I'll get them posted on the website soon. This will require changing all of the waveguides a bit, so if you are relying on using the routing template, I would hold off on downloading any waveguide files right now. You'll know when you can download them when the template files are available, and I always have a revision log at the top of every page where I note updates.



I tried using double-sided tape to hold the template in place, but it didn't stick well. I ended up using a finish nailer to attach. I thought about integrating screw holes into the design, but I like that the finish nail leaves a tiny mark that is easy to fill. Any other ideas for attaching them before I do a final template design?

[Bear]

I tried using double-sided tape to hold the template in place, but it didn't stick well. I ended up using a finish nailer to attach. I thought about integrating screw holes into the design, but I like that the finish nail leaves a tiny mark that is easy to fill. Any other ideas for attaching them before I do a final template design?

That looks a lot like the one I developed. The issue I had was that the jig/template wasn't tall enough to give the following bearing enough material to ride smoothly. I never had an issue with double-sided tape not holding the template in-place, though.

[Steve Manning]

Like Bear, I've never had an issue with double sided tape. Of note, I use the stuff for carpets, so it's pretty heavy duty. Also, you can use painters tape and CA glue. I use it more often now with my CNC, clean up is a lot easier than the carpet tape.

[Efalegalo]

Random Thoughts:

I believe the intent of the elliptical waveguide was to allow for closer c-t-c spacing between the tweeter+waveguide and midrange, correct?

In recent months, I've seen designers challenge this thinking, and suggest using 1x to 1.2x the x-over frequency instead.

According to ErinsAudioCorner - the March Audio Sointuva was the best passive speaker he has measured to date.

Looking at the measurements and design, the c-t-c distance between the waveguide and mid appears to be approximately 175mm. The crossover frequency appears to be around 1,900Hz - 2,000Hz, corresponding to a wavelength of 181mm - 172mm. <-- which matches the 1.0x recommendation. The Sound Power response is superb.

I guess we have yet to test a speaker that employs the elliptical waveguide and achieve similar results.

Thoughts?

[augerpro]

I've finally added router templates for elliptical waveguides to my website! You'll need 5/16" OD and 1" OD template guide bushings to use them. There are holes that will accept #4 sheetmetal screws, or you can use a finish nailer, or double-sided tape to attach them. https://www.somasonus.net/waveguides

[augerpro]

FYI, I ended up going with .stl over 3mf. When I tested a couple vendors, some don't recognize 3mf yet. This is a bummer because 3mf allowed including the engineering units in the file, so there would be no more confusion over metric vs standard. Also, weird internal faces throwing errors were supposed to be reduced because 3mf has a better storage format. Oh well.



On an upnote, wow have prices come down for printing! i.materialise.com quoted me $25 for nylon SLS (my favorite) on one of my 5" waveguides! Now I just have to understand their finishing options, I'm not sure you can "polish" SLS, at least without removing a lot of material.

[tktran]

Random Thoughts:

I believe the intent of the elliptical waveguide was to allow for closer c-t-c spacing between the tweeter+waveguide and midrange, correct?

In recent months, I've seen designers challenge this thinking, and suggest using 1x to 1.2x the x-over frequency instead.

According to ErinsAudioCorner - the March Audio Sointuva was the best passive speaker he has measured to date.

Looking at the measurements and design, the c-t-c distance between the waveguide and mid appears to be approximately 175mm. The crossover frequency appears to be around 1,900Hz - 2,000Hz, corresponding to a wavelength of 181mm - 172mm. <-- which matches the 1.0x recommendation. The Sound Power response is superb.

I guess we have yet to test a speaker that employs the elliptical waveguide and achieve similar results.

Thoughts?

I think those who keep re-stating, ad nauseam, the "closest possible distance" are probably not considering all the details.
And I think that this idea stems from the apparent ideal of a point source.

First off, I'm not even sure a point source is the ideal. Maybe if you're trying to reproduce a square wave, but, I've been to many concerts both live (unamplified) and amplified, and none have a single apparent source. It's more like a multiple apparent sources summed to one very wide and reasonably tall source.

Anyway, going back to multi driver multi ways- any 2 or 3 non-coincident drivers are not going to be behave as point sources. Thus the physical separation distance between the drivers with small wavelengths eg. tweeter and midrange, depends on the desired vertical dispersion or directivity, at the lobes or nulls, and thus is tied to the crossover frequency AND slope.

So it's a matter of trade-offs.

[tktran]

On an upnote, wow have prices come down for printing! i.materialise.com quoted me $25 for nylon SLS (my favorite) on one of my 5" waveguides! Now I just have to understand their finishing options, I'm not sure you can "polish" SLS, at least without removing a lot of material.

What's good about nylon SLS?

[augerpro]

It's way tougher than PLA. And other than surface texture being like sandpaper, the dimensional accuracy and lack of defects is very good.

[augerpro]

Bliesma T34B fans, rejoice! Here are the results of two 6.5" waveguides. One has a circular mouth and the other elliptical. Now that I have a basis for further designs, I'll be doing a 8" and maybe 7.25". You can download the files here: https://www.somasonus.net/bliesma-t34b

[JonMarsh]

That's looking mighty fine, Brandon! Personally, I'd be very interested to see what an 8" circular version looks like.

Have you been working with Marcel's tools for waveguide design? I've got the whole kit and caboodle download, and have been reading his documentation in "stolen moments" but just finished the move out process yesterday and now still have a lot of work to do getting organized for my "work" in the new place- I've been keeping the other half busy doing fix up stuff for her, so she's pretty pleased with how things are looking and working that SHE cares about!

My impetus for Marcel's stuff is the T34B's and T25B's I have...

I'm going to hit that download link right away!

[augerpro]

Yeah 8" variants are next. If you have a printer I can send you the .stl, you might get around to measuring it before I do. I'm not sure why the elliptical took a step back in performance from an earlier version I posted, they are identical other than this had the additional depth already included by the shim I used on the last one. I like to test with shims since I can tweak depth without printing a whole new waveguide.

I've worked with Marcel's software - great stuff. But, it is currently limited to spherical sources, (plane wave won't represent dome tweeters). By a stroke of luck, the SB26 and T25B modeled well, I think I posted the results earlier for a 5" sim vs my own measurements. I was able to try out some different contours and depths and cross off a few ideas I had when they simmed worse. For example, OS contour did not work well with either. But the T34B and most depressingly, the Peerless DA25 corundrum dome, are so non-spherical that I could not get any match between sim and reality. Real bummer, that Peerless would have been a fantastic candidate for a low cost but high end speaker using all partsexpress parts.

[JonMarsh]

Hey Brandon,

I don't have a 3D printer - yet- though it's something that's been on my mind from time to time. It just keeps getting swamped out by higher priority stuff at the moment. So, while my main CAD program can read STL files, a STEP file is most useful, because I can import it, do a cross section and extract the profile, and then create a waveguide component structure suitable for CNC fabrication.

Steve and I did this back in late 2016/very early 2017, and had a pretty nice part using a profile I empirically created based on past experience, and the results were fairly encouraging- so of course, Dayton discontinued the RS28a. The replacement RST tweeters don't work nearly the same in the top octave or for consistency on and off axis. An important factor in the behavior in the top octave is that the RS28a DOES have an integral phase shield, which impacts the loading into the wave-guide, and for whatever happy accident or reasons, Usher did it right (by accident) for working with a waveguide.


The profile is sort of similar to the Dutch & Dutch 8C, though as far I know that didn't exist commercially back then.


I've got about 8 NIB of the RS28a, though... enough for a special "limited production" item?

:rofl:



So one of the lower priority projects is to build on that effort, with newer tweeters like the BlieSMa series. One thing I have a hunch about with them is that they work better in wide frequency range loading in waveguides due to the very narrow surrounds. I have a T34A in a Visaton waveguide that has flaws in the smoothness of response, but I think with a different profile would show a lot of potential- your work here confirms that. Tracking of the upper octave off axis is a biggie for me- one reason I don't think the Faital CD horns are comparable to Eighteen sound. But just look at the response of the SB TW29BNWG-4 off axis at higher frequencies. Big wide surround. I'm probably being simplistic, but sometimes a simple explanation has some truth to it.

[augerpro]

I attached 8" circular and elliptical waveguides for you to try. I hope you have luck with the T34A. The T25A dome has very different geometry than the -B, and didn't work out well with the waveguides I had made. CNC in plastic first

[Scottg]

All I ask is that you not post it on Diyaudio..

https://www.newark.com/audible-physics/220-cp/2-carbon-impregnated-paper-fullrange/dp/84Y8036?mf=147056&krypto=pfwhfZzK9FbtNPycefR347gv5ZhgSDf1CH23LhVc29uWOHEPCRS4fatSGUR%2FBGjfXhxkdL6Ukxwr0MbE7hjjxcyP%2BCWg%2BhGWAXV3TYnCvUleyiNwi6hIKueTZtne2Kh0KFhdKUucOYIPnO6usDuVIRVv9IdRynUd147vH36fQjx7x7kC4bTb177JEcDq3Yag8n60uSZUY61bm8plOizm1O66mjZKxc9GixgUX6CElP%2BCtLkU4r3g5fELlclMR%2FD8EAkuvhLa02qPq6j32DAxE9zT1dxrC22q2q72d8f6%2BWjkjdn9VX3jMb3c%2BOUh60YMTGAsqKU4%2B2k0K0bDxFbNeRFdYs1TLrtgqFsaeWfCY6HUOmUxWZYC03cxGXQ8DTMzvYdmSDPyyC%2FLMog3km6daXBG8ohqCsjgvO7oE7PUyWoPfd1hf0AQTuqDnBL4TIMDrT2EG3FKTiyZMsL2C7MAVixYDqYDyIbiVPaMElT%2FWCRE9fNFu7%2FSZY8SOlCGxmbNDytp1P0UkjQOCWHhgT5Wy3HOFc4Yk9MFzdH9q9q%2FIT%2FviBz4pg6xRq%2Bu9HMBnYJHBW6oqHLksz%2BWaN%2FOpeXz3h%2BEyjyNwpZBhtwwsEz%2FYnX9t0Kfl6jdrrKwCciDnuOmqSFMVtyduac0BejYKTgRXXStan6P6gaqxA18bpcvVPcsnSlpUkT1eQ2uvvOYK3Y9&ddkey=https%3Aen-US%2FElement14_US%2Fc%2Faudio-video

[augerpro]

Someone already did. Can we take this to PM so we don't sidetrack this thread?

[JonMarsh]

Someone already did. Can we take this to PM so we don't sidetrack this thread?

If you're responding to me with that request, certainly, no problem. BTW, I haven't had time to get to this, yet, an awful lot of other stuff in the task queue ahead of it.


Ah, I see, I think you're talking about the 2" full range.

[augerpro]

Yeah, I was responding to Scott

[augerpro]

Ok, here are the 8" waveguides for the T34B. Also included a new 6.5" elliptical mouth with a higher aspect ration (1:.83). Also included a new 6" elliptical waveguide for the T25B (used my new family of speakers). I've decided to revisit the circular mouth on the SB26 family. The first is a 6.5" model, and it looks good, I'll move on to the other sizes when I have time. I've updated my website to include the new designs.

[Evil Twin]

Clearly you are making interesting progress- several of these designs look quite useful for high order crossover points around 3kHz.

[DaveFred]

Just tossing my $0.02, I've never gotten a satisfactory (to me) waveguide setup working with the DA25, and have tried several approaches.

I think there are characteristics we/I don't yet fully understand (gross understatement) about how the the interface between a dome of a specific curvature with a specific size surround works with the immediate throat area of waveguides in the frequency range of 8-20kHz. That's always where I see the most "unexplained" or "unexpected" variation.

Note, what you're seeing with the T34B BlieSMa mirrors my own experience to an extent with the T34A; however, I'm using a different waveguide, maybe a bit less fall off, off axis out to 45 degrees. The very narrow surround is a GOOD THING in my opinion. As an example of why a wide surround is NOT a good thing,

But hey, I haven't been working this area much lately, still too busy trying to get settled with the relocation - that process will continue through the middle of next year, should close on the house in construction in March.

And I would redo this measurement after things get setup- but this gives an idea of the issues.


[ATTACH=CONFIG]31625[/ATTACH]



I rather prefer the results of a T34A with a cheap Visaton waveguide (148R)

Are these the results from the T34A in the 148R?