Waveguides for 3D printers and CNC's

[Steve Manning]

Probably 30-ish hours. I don't know about sanding these things, it's all new to me. I think the current situation is if you must have a smooth finish either use a commercial outfit and print in SLS nylon, or use a CNC. As technology advances hobbyist 3D printers will also get pretty smooth, but it's not currently there as far as I can see. I mean you could try a tiny nozzle which would enable higher resolution in the slicer, but print time would get much longer. I should try a test with .02 nozzle.

That's a chunk of time ..... I was just curious of how it would compare to my CNC. Thanks

[augerpro]

BTW since the Bliesma designs went so well, I didn't have to spend a ton of money. If I can reach my gofundme goal of $750 I'll buy the 3/4" Scanspeak d2104/7120-00 and 1" Scanspeak r2904/7000-05 and start working waveguides for those. I did a circular waveguide for the 1" Scanspeak ring radiator for the Monkey Box project and it came out well so I'm hoping it will be easy to do more variants. A big 8" waveguide to go deep might be a nice match!

[ergo]

Prusa Slicer started to support the progressively thinner slices at some point like I showed here here

Not sure what slicer Creality uses and if it has same option.... but with that enabled and printed in PETG the sanding after is similar to what one would need to do on hardwoood CNC. MDF on CNC would be easier to sand than the PETG plastic as the plastic gets harder.

Ergo

[Scottg]

..I think the current situation is if you must have a smooth finish either use a commercial outfit and print in SLS nylon, or use a CNC. As technology advances hobbyist 3D printers will also get pretty smooth, but it's not currently there as far as I can see..

https://www.youtube.com/watch?v=UwN4gL-my4w&feature=youtu.be&t=282

-with any filament though, you have to be careful about moisture content.


Note: "larger" SLA (actually LCD) machines are starting to get more affordable, I just got a pre-order on the Anycubic Photon Mono X, but even that will require an *"assembly" design for most prints. The Peopoly Phenom would work for most prints without assembly. Also, there are an assortment of different resin materials to choose from - Anycubic even has some out that are low VOC.

https://formlabs.com/materials/

*https://www.youtube.com/watch?v=FzCm1iTf8PA

Note that with resins, you can use the resin itself (same resin as the model) as the binder/glue provided the resin was clear enough for UV to enter-into the model for the binder/glue stage to set: making the piece monolithic including the material.

[augerpro]

The SLS nylon process I like doesn't use resin. It's actually powdered nylon that is fused by a laser. Very stiff and strong, and the layers can be imperceptible. Sort of feels like a 200 grit sandpaper surface finish though. I think HP makes the most popular model.

[Scottg]

Yup, I know about SLS. (..and nylon is very strong, though I'm not sure if that matters in this use-case unless it's a very heavy compression driver attached to horn/waveguide.)

I was just suggesting alternative methods for better quality prints from home.


You could probably also reduce the cost of *any print simply by making the rear a structural/bracing void and then filling-in with a cheaper material (like perhaps caulk).

*home or commercial SLS printer.

[augerpro]

I've updated my website to include the Bliesma T25B and newest versions for SB26 and SB21.

[augerpro]

19mm Revelator in da house!



A number of you wanted to know my slicer settings, but now that I've redesigned the phase shield and started printing face-up, there really isn't anything special. Layer height: .12mm, top and bottom layers: 4, perimeter shells: 4, max fan speed for bridging, random start points on perimeter. The main thing is to generate supports under the throat so that interface to the tweeter is round and flat. Filament brand makes a difference. I had a tough time removing Hatchbox supports from the phase shield, while eSun PLA+ supports come off with less effort and more cleanly.

[Bear]

I posted this over at DIYA, but I'll also post it here. In the spirit of "I'm an idiot with a little too much, and yet not enough, budget"....

My current project is a 6+1 (oh, no! not another one!) using the SB17NBAC and the SB26. I made a jig for routing the recess and the through hole. On attempt #1 and #2, I used top-bearing bits, but these turned out not to be stable when cutting very much material at all (ignore the use of the word "dado" in any of the cheaper bits). As a result, my bit ate into the jig, making it useless (not a smooth cut any more), and I had to trash baffles #1 and #2. For round #3 and #4, I was more careful with the bit, but I still got uneven results. In addition, I ended up burning the bits just a little.

The good news on round #3 and #4 is that after I bought a 1.25" guide bushing, cleaning up the through-holes was a snap. Not only did the guide bushing work as advertised, but it allowed me to use my 0.25" helical upcut bit, which is a LOT better suited for this than the trim bits. My jig is a little too short to allow the bushing to bear fully on top of it, so I increased the height to 1/2", which matches the height of my bushing. This is a trivial step to do in TinkerCAD.

This is what the through-hole looked like after machining with trim and dado bits. The rebate was relatively clean (aka usable), but the through-hole was jagged. Double-sided tape is pretty much mandatory if the jig is going to take any lateral force.



This is after running a 0.25" spiral upcut bit around the jig with a 1.25" guide bushing. This was what I had hoped to achieve with the jig. For round #5 (cabinet #3), I'll cut the through-hole first using the guide bushing, and then use a 0.5" rabbeting bit to cut the rebate.




Here's a zip file with my jigs for the 4" and 5" SB26 waveguides.

SB26 Routing Templates.zip

[Steve Manning]

Nice Bear ..... I did something similar when I did the Minerva's. One suggestion, if you haven't already, get yourself a spring washer for the guide bearings. Like I used here .... https://www.htguide.com/forum/showth...hlight=minerva, post 368.

It will save you, trust me.

[Bear]

Nice Bear ..... I did something similar when I did the Minerva's. One suggestion, if you haven't already, get yourself a spring washer for the guide bearings. Like I used here .... https://www.htguide.com/forum/showth...hlight=minerva, post 368.

It will save you, trust me.

Thanks, Steve! I've got one more baffle to do tomorrow (shop slots were filled this weekend), so it's doubtful whether I can snag a spring washer in time. Otherwise, I'll use caution and have that for the next time. Do you have a part number or description from MLCS? If not, I can start dumpster diving to find the right one.

Speaking of your Minerva build.... Since I'm going with a small, sealed cabinet (designed specifically for no lower than an 80Hz cross to a sub), I don't have a lot of room for crossovers in the cabinet. I'm going to use 4 pole SpeakOn connectors to link the cabinet with an external crossover box, similar to how you had your crossovers in the stands connect to the Minerva speaker cabinet. Any tips/tricks there are also greatly appreciated.

https://www.htguide.com/forum/showthread.php?43049-Minerva-Monitor-quot-Patience-my-ass-I-m-going-to-go-build-something-quot&p=626754&viewfull=1#post626754

[Steve Manning]

The bushing spring is item #9044, https://www.mlcswoodworking.com/shop...mpguide_anchor

As far as tips on the stand ..... threaded inserts are your friend. It lets you build the crossover on a separate board and then mount it inside the stand when your ready. Their a little more work than just gluing everything together, but if there's an issue it makes it so easy to take things apart.

Those SpeakOn connectors are nice as well.

Do you have a design for the stand yet?

[Bear]

The bushing spring is item #9044, https://www.mlcswoodworking.com/shop...mpguide_anchor

As far as tips on the stand ..... threaded inserts are your friend. It lets you build the crossover on a separate board and then mount it inside the stand when your ready. Their a little more work than just gluing everything together, but if there's an issue it makes it so easy to take things apart.

Those SpeakOn connectors are nice as well.

Do you have a design for the stand yet?

Thanks for the part number. For the immediate future, I'm going with some cheap, powder coated stands from PE, and then I'll build some small boxes for the crossovers. Realistically, the first few prototypes will be done inside my miniDSP 2x4, and then drop that to analog once I'm close to final. I'd expect to worry about stands sometime in May. Which year that May will occur is a secondary question.

[Dave Bullet]

Hi Brandon, Have you given any thought to less infill (to reduce cost) and opening up the tweeter mounting aka Visaton WG148 so you can nut/bolt mount the tweeters? instead of screw in? (might open up material choices for those less brittle and allow remounting without wear and tear)

[augerpro]

Infill is up to the printer, it's not something I have anything to do with. I'm not familiar with Visaton mounting system. What are they doing?

[Dave Bullet]

Excuse the terrible photography. I think your model has 100% infill? I'm not sure how much less the Visaton WG148R is as shown. There are sites that will hollow out an STL. It made a 60% cheaper quote for me on one of them by doing so. I never proceeded because I decided it might be a little weak

AS you can see there are threaded inserts. but these could simply be holes to support thread and locknut applications (clean through the guide underplate or whatever you call it that mounts to the tweeter dome assembly / faceplate)

[augerpro]

I see. Interesting idea. I suppose it could be done easily enough in the model for a specific nut that can be glued in.

There is no infill spec in the .stl or .step file, they are just surface models. The person printing it sets the infill in the slicer software. I have been using 30%, but would probably go more for a final product to be used in actual speaker.

[augerpro]

Here's an update of new designs for the T25B, SB26, SB21SDC and SB21RDC, Peerless OT19, ScanSpeak Revelator D2104/7120.

[augerpro]

So I was playing with ABEC and modeling 6" waveguides for the T25B. I wanted to see how a circular mouth might behave even though everyone here preferred the closer CTC of the elliptical mouth. First plot is the 6" vD from a couple posts above and the ABEC model of that waveguide. Following that is a 6" round waveguide with a profile of constant radius, the same radius in fact as vD's horizontal radius. Then I modeled another 6" using an OS profile.

[Paul Ebert]

Has anyone started working with the T25B in the waveguide? I'm wondering how low it can be used. I'm looking for a good match to the PTT6.5 and hoping to cross it at 2k or below. I don't think the stock T25B works very well that low, but perhaps in a waveguide it might?

[augerpro]

I did a demonstration of the T25B here: https://www.htguide.com/forum/showth...l=1#post637137

I think aimed for 1800hz in those examples and they'll do that, but probably not much less.

[Paul Ebert]

It looks to me that the waveguide boost is around 10 dB between 2k and 3k. Is it safe to assume that the distortion in that region would be reduced by that amount when the crossover is added? If so, that would be very welcome! It might make the T25B a good match to the PTT6.5 with a crossover target of 2k. That would save quite a bit of cash compared to the T34B.

[augerpro]

It should be at least 10 dB lower distortion. Hard to say how much since it is by nature non-linear.

[augerpro]

Small update of 8" waveguides. I've noticed there is something about big waveguides that make problematic tweeters work well. Not sure if it is the mouth size or depth. I'll get the files uploaded to my website by the end of the weekend for this and the last batch of testing since they all came out well.

[augerpro]

My website is updated with the newest results and files. BTW if anyone has good pics of their waveguide, I'd like to include more on my website.

[hifi-alex]

Do you think that the Bliesma T25A-6 (AlMg version) would behave similar to the T25B-6 in your waveguides?

Cheers,
Alex

[augerpro]

Do you think that the Bliesma T25A-6 (AlMg version) would behave similar to the T25B-6 in your waveguides?

Cheers,
Alex

I'm not sure, I have heard the dome geometries are a bit different. If you have them and want to send me one I can measure it.

[hifi-alex]

I'm not sure, I have heard the dome geometries are a bit different. If you have them and want to send me one I can measure it.

Not yet and I'm afraid shipping costs over the ocean and back might be too high

[Bear]

I'm not sure, I have heard the dome geometries are a bit different. If you have them and want to send me one I can measure it.

I grabbed two T34As and a T25A from Solen during the sale. PM me your deets, and I'll send you the T25A once it arrives next week.

[Concillian]

Got one of my test boxes finished last weekend with 2 baffles so I could mount my SB26ADC with the standard faceplate flush mounted and with the 8" version C waveguide flush mounted. Baffles did not have the woofer hole cut out yet, but had the woofer rebate cut.

I am using a Hypex Fusion FA253, so the DSP makes testing a breeze. I mounted the tweeter in the waveguide baffle and put that on the box, then EQ'd flat from 700-12,000 Hz (a shelf on both ends with one small PEQ at 10kHz), then applied an LR4 @ 1000Hz.

Then I swapped the baffle and re-mounted the faceplate and measured the flat mounting with the exact same tweeter, but with no EQ and the same LR4 @ 1000Hz. Measured with REW & UMIK-1 no gating at about 1 meter to the baffle (not 1m to the dome, so the WG mounting was slightly further away.)

Here is frequency response for both showing similar levels until 12k with a 3db difference for a bit above that. The flat mounted was run 3dB higher volume on the Hypex amp, so I guess I should EQ flat out to 16k instead of 12k, but whatever, this demonstrates what I wanted to see well enough.



Distortion Performance looks ridiculously good for both given the low XO and high SPL level. I was surprised how good the distortion was without the waveguide. I have not checked the UMIK against another reference for SPL, but my ears and family confirm it was loud enough that 100dB seems quite a reasonable estimate.



I was planning XO in the 1400-1700Hz range @ LR4 to an 8", this data seems to confirm that's totally reasonable. I thought others in this thread would be interested in this information.

[xandresen]

My website is updated with the newest results and files. BTW if anyone has good pics of their waveguide, I'd like to include more on my website.

I tried ordering the 5x.75 waveguide for the SB26 using the latest .STL files from SomeSonus, sending them to 3dHubs.com. They can do the HP nylon process which I plan to use.
Their analysis of the files gives a manufacturability error, with and without the phase shield:
"Mesh integrity
0 non-manifold edges
0 boundary edges
362 intersecting faces" (number varies between w/ps and no/ps files)

The .STEP file for the waveguide without phase shield does not give an error at 3dHubs. Good.

However the SomaSonus website does not have a .STEP file for the 5" with phase shield and I would prefer the phase shield.

Final thought. I sent the .STL file to a cheap vendor who has no analysis and they made PETG prints that were so bad they didn't even ship them, just sent photos and gave me my money back. Don't know if the file errors had anything to do with that.

Any suggestions?

Thanks.

I did get a 3D print of the routing template from another vendor in a much cheaper PETG process. looks usable.

[augerpro]

I just printed the 5" vJ on my home printer and it printed fine. The mesh model looks good, no surfaces on the inside of the body. I've found all that can be good and 3dhubs will still pop up a errors, but it prints fine. Xometry doesn't give any errors. PETG is harder to print with and your low cost printer was probably a hobbyist.

I'll get .step files up for everything, but that will be awhile with the new job keeping me busy.

[augerpro]

i.materialise.com didn't throw an error. Prices are cheaper there too.

[xandresen]

i.materialise.com didn't throw an error. Prices are cheaper there too.

I got quotes from Xometry and i.materialise without errors for the .stl file.

Thanks for your help, and the enormous work to create these designs!


Finish (nylon/polyamide)
i.materialise offers a polished and dyed black finish for only $4 over the dyed black finish.
I'm not going to risk the polishing for my parts with the delicate phase shield.

[augerpro]

Great! Be sure to post some pics when you get them. At those prices and with all the finish options, I really like what i.materialise offers.

[augerpro]

Finally done working out of town, so now I can get some testing done and answer all the questions piling up.

I've started some designs for the Scanspeak D3004/6600 and R2904/7000. These will all be 6.5" width mouths and greater as I've found these large diaphragms just don't behave well in small waveguides. And with the extended low response and great HD behavior, it just makes sense that most people would be looking to cross these tweeters low. I'm also going to revisit circular mouths. When I first started testing performance went up a lot when I switched to elliptical mouths, but other design properties were still unrefined and so I want to make sure elliptical is still the way to go with my current knowledge. Also, I've seen some people get reasonable results with tweeters I've used on circular waveguides like the Visiton, and I want to understand why that is.

First up are the 6.5" waveguides:













The circular mouths are looking pretty good. I'll need to continue this investigation and create versions for the other tweeters I have once I nail down some best practices. Another thing to note is I'm going to improve the tweeter/waveguide interface. Right now there is a bit bigger gap than I'd like right at the throat.

[augerpro]

Almost forgot I did a circular guide for the T25B. Here is a 6.5" followed by the elliptical version from a few months ago.

[Reet]

Just want to say thanks a lot for your work in designing these waveguides and making the models freely available. I had a friend print a couple waveguides for the CSS LD22 and although the prints were pretty rough, after some sanding and paint they look pretty darn good. Hopefully I can find some time to put them to use this fall.

Just an FYI for anyone reading, if you ask CSS nicely they'll sell you the LD22 "unassembled" with the faceplate unglued.

[Bear]

I did get a 3D print of the routing template from another vendor in a much cheaper PETG process. looks usable.

The most reliable results I achieved used a guide bushing, but then you need to have the height of the template be tall enough to fully accommodate the height of the bushing. Making the template drawing is a trivially easy step with something like Tinkercad. Turn the existing waveguide drawing into a negative space shape, then intersect.

After you make the through-hole, then come back with a rabbeting bit to create the recess. The fit wasn't as tight, but the process was more confidence-inspiring.

[Bear]

Almost forgot I did a circular guide for the T25B. Here is a 6.5" followed by the elliptical version from a few months ago

Let me know if you're still interested in the T25A for comparison. I boxed mine up, but it never made it to the UPS/FedEx store for shipment.

[augerpro]

Let me know if you're still interested in the T25A for comparison. I boxed mine up, but it never made it to the UPS/FedEx store for shipment.

Heck yeah send it!

[Bear]

Heck yeah send it!

I'm traveling through the weekend. Let me get back home, and I'll try to get the box to FedEx this time....

[augerpro]

I've updated the T25B files at my website to include the new tweeter interface from a few pages ago.

[augerpro]

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.

[augerpro]

I've also started working with the Peerless DA25TX00 "corundum" dome tweeter. The first results aren't worth posting but confirmed my fear that the challenging throat interface is going to be critical to do exactly right.