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-   -   Open source Waveguides for CNC & 3D printing! (https://www.diyaudio.com/forums/multi-way/318190-source-waveguides-cnc-3d-printing.html)

Shaun 1st September 2018 08:21 PM

Quote:

Originally Posted by augerpro (https://www.diyaudio.com/forums/multi-way/318190-source-waveguides-cnc-3d-printing-post5527245.html#post5527245)
SB26ADC in 5" G and SB21SDC in 5" A in .STEP format, which should be easier for the CNC people:

Dropbox - 5x.75 G SB26 v5.step
Dropbox - 5x.75 A SB21 v5.step

And SB26ADC in 8" C, .stl and .step:

Dropbox - 8x1.5 C SB26 v3.step
​​​​​​​Dropbox - 8x1.5 C SB26 v3.stl

Thank you for sharing your excellent work. Would you mind also making available the stl files for the two 5 inch waveguides?

augerpro 1st September 2018 08:55 PM

They should be posted a few posts back.

ScottG> That does look interesting, thanks! I wonder how the dimensional stability is?

ScottG 1st September 2018 09:57 PM

-depends on the resin and its hardner (..assuming it has fully hardned).

You could use almost any resin really that fits your needs. Smooth-on is best for it's specialty products but particularly for it's form material.

The most obvious resin from them would be this (..and it has its technical detail at the right of the page):

EpoxAcast™ 650 + 101 Hardener Product Information | Smooth-On, Inc.


-as far as cost is concerned though, I'd probably experiment with cheap gallon epoxy and hardner and use urn-sand as filler/media. Once you get the balance right it should be very inexpensive overall. Consider a large form with multiple waveguide forms - like a super-sized silicone cookie sheet, and a resin mixture with a lot of urn-sand (as a percentage of the resin's volume) and I'm guess that the total cost would be less than $5 to produce each waveguide (for materials), ..and more likely half that. You could do it even cheaper with cement (as opposed to resin), but cement shrinks and is prone to cracking (and it probably wouldn't bond well to the phase-shield).

Note that the gallon unit of the Smooth-on is still a good price, but remember that it already has its sand filling included - so a lot of the volume is cheap sand, NOT resin:

Buy EpoxAcast(R) 650 and EpoxAcast(R) 650 BLACK Mineral Filled General Purpose Casting Epoxy from Reynolds Advanced Materials

ScottG 1st September 2018 10:24 PM

-oh, one other thing I should point out with resin's is UV stability/yellowing.

Some have enough, some don't. so it makes the search a bit more difficult. Though of course there are additives for this. (..and the hardner is typically the source that yellows the most.)

Bare 1st September 2018 11:21 PM

What ! No JBL " ButtCheeks " ?

next667 2nd September 2018 08:46 PM

How do you actually fix tweeter to wg?
Remove screws, take off face-plate, center the wg onto 4 extruded cylinders (protrusions), or are those just spacers?...
How does it actually hold together? Tape?
Final step is sealing with putty?

augerpro 3rd September 2018 02:32 AM

Quote:

Originally Posted by next667 (https://www.diyaudio.com/forums/multi-way/318190-source-waveguides-cnc-3d-printing-post5534264.html#post5534264)
Remove screws, take off face-plate, center the wg onto 4 extruded cylinders (protrusions)

Exactly:

https://i.imgur.com/drhP694.jpg?1

mbrennwa 14th September 2018 11:28 AM

Waveguide newbie...
 
I am new to this thread and to waveguides in general, but I do understand how waveguides can do good things for tweeters.

I am currently juggling different ideas related to the Open Source Speaker design over here, and I believe a tweeter + waveguide might be interesting for this project. To get myself into waveguides I got myself a few Visaton waveguides (they were cheap) that I might stuff onto some ScanSpeak 6600 tweeters that I have in my parts box. Those parts don't quite fit, but I will solve that somehow (using the tried and tested MacGyver approach) so that I can have a play with it.

I don't expect this to be the final/best solution, and I actually prefer Be dome tweeters like the ScanSpeak 6640 or the Satori TW29BN. From screening this thread I tend to believe that those tweeters don't play well with (custom?) waveguides. Is that correct? Why? What makes a tweeter a good tweeter for waveguides?

augerpro 14th September 2018 04:43 PM

It's not really anything to do with the dome material. It's the size of the dome that is the issue, and all of these Be tweeters just happen to be on the larger side - 29mm. And with very large surrounds making the throat even wider and pushing the reflections/nulls down in frequency into the 10-20khz area. If you could get the diameter at the outside of the surround to 1.3" or so, you would be in good shape.

mbrennwa 14th September 2018 06:04 PM

Quote:

Originally Posted by augerpro (https://www.diyaudio.com/forums/multi-way/318190-source-waveguides-cnc-3d-printing-post5545723.html#post5545723)
It's not really anything to do with the dome material. It's the size of the dome that is the issue, and all of these Be tweeters just happen to be on the larger side - 29mm. And with very large surrounds making the throat even wider and pushing the reflections/nulls down in frequency into the 10-20khz area. If you could get the diameter at the outside of the surround to 1.3" or so, you would be in good shape.

I see... but: the ScanSpeak 833000 seems to do pretty well in a waveguide. The 833000 is specified with an (effective) dome diameter of 32mm, whereas the ScanSpeak 6640 and 6600 have a smaller dome specified at 30mm. Is there hope?


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