3D printed waveguides

[augerpro]

Roland (Ro808) connected me with another gentlemen that can model waveguides. We have started with simply modeling my elliptical C from a number of pages ago, to make sure the sim correlates well with my measured results. Here are the results. This is with no phase shield included. My elliptical C:



Christoph's sim:


Overlay:


This is better than I could have hoped! Hopefully Christoph will be able to share his effort and we can formulate good designs int eh sim first, and just print the best to verify!

[philthien]

That is really pretty remarkable.

[scottvalentin]

Wow - that is about as good as you could possibly get! Outstanding!

[DanP]

That's a pretty darn good correlation!

[bcodemz]

Wow that's a really good correlation. That sim tool would be incredibly useful for waveguide design.

[ergo]

This looks really great!
I've tried to look for suitable simulation tools for a while and have not seen one in reasonable hobby price range. Is this done with some fancy tool like Comsol Acoustics module or such or is this something from DIY domain too?

[augerpro]

ABEC from what I gather. Going to try it myself and see what I can do with it.

[natehansen66]

Awesome! Think I may know who Christoph is. Impressive results. Would it be possible to rescale your graphs? It's difficult to see detail on that huge scale SE likes to show.

[augerpro]

Nate> I just ran across a thread you started and yes, he is Gaga. I'll probably keep publishing initial results with the scale like it is for consistency, and I like it, sometimes people get so close it is hard to make sense of all the squiggles. But if someone wants to see a smaller scale of any particular design (or plot the info differently) just let me know, easy enough.

[augerpro]

Here are results for the SB26 5" waveguide version F, and the SB19ST 5" waveguide version A. I'll get the TW29RN and N26CA out over the next couple days.

SB26ADC:



The midband is much smoother over previous results due to the .02" lip I incorporated after shims and putty showed the faceplate was not sealing well against the mouth of the waveguide:


Speaking of sealing, in actual use you want to seal a couple gaps on the tweeter that do not seal like you might expect. I would use blue tack putty, easy on ,easy off:




The SB19ST:



Unsurprisingly the phase shield was slightly worse with a fabric dome. OTOH I didn't expect that on axis dip even without phase shield. I believe the shape of the dome requires another look at throat angles as this a small diameter but tall dome. Nearly a 180 degree hemisphere. I'm *guessing* I need to relax the throat angle some.

One thing I've noticed so far is that everything looks much better on the 8" waveguides (results coming soon). I guess I assumed that a little waveguide would cause little problems, but that does not appear to be the case. In fact just going to say, 6" wide waveguides might solve a lot of the top octave issues I've had to solve. But I had to start somewhere!

[Mike220]

Amazing work on this project Auger i have thoroughly enjoyed this thread and its made me want to try a few guides in my next builds.

[augerpro]

Here are the results for SB26ADC on the 8" waveguide. Note, I usually measure with and without phase shield, sometimes with a shim between mouth and tweeter, and sometimes check vertical responses on more promising/new designs. All of this is noted in the screenshot.

[augerpro]

Much awaited results on the Transducer Lab N26CA! Probably the best of the bunch on the troublesome 5" waveguide. I think the squiggle around 10khz is a similar to issues I had with the SB26, might just need a small lip and/or some tape on the mounting face to stop vibration. Wish these weren't NLA, moving up in size will probably make some beautiful plots.

[augerpro]

Here is the TW29RN on both 5" and 8" waveguides. With pinned center it's no surprise the phase shield does nothing. The top octave has me miserable. The difference version A and B is slightly different wall radius.

[augerpro]

For anyone unfamiliar with the natural response of a horn loaded driver, here is the N26 after some simple filtering to flatten the "tilt":