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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)

augerpro 7th May 2018 03:29 AM

I'll have to play with the shims again with the newest prototypes to revisit this, since your sims show some area for improvement.

I do notice though, that the examples with no/low step have quite constant directivity up to 10khz. While the others drop faster with higher frequencies much as a normal tweeter. Better? Just different?

How did the profile differ from my design C? Have you played with design G yet? I did experiment earlier with using an ellipse as a profile. Compete PITA to model. The results were decent, but that was with earlier, cruder designs, so maybe I need to revisit that also.

I also ought to look at rounding over that small step transition to the flare.

Gaga 9th May 2018 09:45 PM

Hi,

Quote:

I do notice though, that the examples with no/low step have quite constant directivity up to 10khz. While the others drop faster with higher frequencies much as a normal tweeter. Better? Just different?
Very good question. I do not know, but would be interested to get opinions here.

Quote:

How did the profile differ from my design C? Have you played with design G yet?
I'll post the differences and will give an update on design G soon. Did some simulations but had no time to summarize yet.

Quote:

I also ought to look at rounding over that small step transition to the flare.
Fully agree. That's on my to do list as well.

bwaslo 9th May 2018 10:39 PM

An opened-source design for a partially 3D printed horn
 
5 Attachment(s)
Here's my basic design for a Unity horn type 3D printed throat in case anyone wants to take on the task.

STL file for printing:
Attachment 679677


It's intended to use two (or one) 4" Celestion midrange TF0410MR and a 1" compression tweeter. A dome might work for the tweeter, but the midrange level would of course have to be greatly attenuated if so. The ends are designed to be extended with plywood to make any size horn you want to go for, adding woofers onto those panels for operation to below the 350Hz that the Celestions will work to. The plywood edges that meet the printed plastic piece have flat 90 degree edges for simpler cutting, but the edges where the wood panels meet each other will need angled cuts at least on two of the pieces.

The mouth end bevel cutting, if any, is up to the builder depending on how he wants it to end. More adventurous builders can put on a second flare (like in the SynergyCalc spreadsheet) or even a curved mouth expansion. This is how I was planning to use it:


(I'm probably not going to build these myself now, even after printing the the plastic pieces and getting drivers, since realizing that I have absolutely nowhere to use or store something like those!)

You'll need a printer with a print area of at least 300mm x 300mm x 200mm high. If you print it with the CD mount end down, it can be done without using supports. I printed with a 1mm nozzle and PLA filament to make for more reasonable printing times and a stronger part. You might be able to find a way to split the part to print on smaller printers, but you'd almost certainly need supports in that case.

If anyone uses this to make a horn, please post photos!

augerpro 9th May 2018 10:54 PM

Thanks Bill! A Unity/Synergy horn is definitely on my to-do list. Maybe next year. Have you quantified the differences with a curved mouth?

augerpro 9th May 2018 11:00 PM

BTW the SB29 fabric dome is the same diaphragm size as the TW29RN so I'll put that on the 8" guide and see how it looks. Also ordered the new Dayton RS28's and new SBA SB21 fabric dome. Small diaphragm, copper in the motor, fabric, might be pretty sweet.

bwaslo 9th May 2018 11:04 PM

Hi Brandon,

No, not really. But at the sizes I was planning to make, the more rapid flare for that would happen pretty far down the horn, so wouldn't do much until lower frequencies where room effects go all goofy anyway. So I wasn't worried too much about it. Doing that or going with a 2nd flare would make for shorter horn, though (a good thing based on horns I've played with, though there are some strong opinions out there to the contrary).

bwaslo 9th May 2018 11:17 PM

BTW, there will most likely need to be some "fillers" in the center of the midrange driver areas -- about 80mmD, 5mm deep or so disks that can be printed and glued there to take up some front volume. I left them off of the STL, intending to test first with some clay to figure how much. The similar horn throats made for the 3D printed NotAsSmallSyns horns I built used a very similar arrangement, though the mid ports had to be moved down a little way for these stubs so the tuning might vary a little -- I was trying to design something that would work with injection molding.

(edit: Tweeter end was designed to match the exit angles of DNA360 or DE250, btw.)

Rokytheman 10th May 2018 07:45 AM

Keep up the good work. For sure some interesting stuff to read about.

Gaga 10th May 2018 07:11 PM

Elliptical Waveguide TypeG
 
6 Attachment(s)
Quote:

How did the profile differ from my design C? Have you played with design G yet?
Here are simulations of design G with the new SB26ADC geometry (see post #80), with the step of design G and without the step, i.e. the SB26ADC membrane directly fitted to the WG contour.

Waveguide Type G looks like this:
Attachment 679839

The respective image within ABEC, WG TypeG with SB26ADC:
Attachment 679840

Horizontal radiation normalized to 0 (with step as shown above):
Attachment 679841

And the respective SPLs from 0 to 60(with step as shown above):
Attachment 679842

Just as a 'control', the simulations without step, i.e. with the SB26ADC directly fitting to the WG contour:
Attachment 679843

and
Attachment 679844

Pretty much the same effect of the step as seen before.

Next steps probably...
Quote:

rounding over that small step transition to the flare
...and variations of the WG contour.

bwaslo 10th May 2018 07:21 PM

1 Attachment(s)
Hmm. a helpful moderator seems to have reformated my post (#83 Open source Waveguides for CNC & 3D printing!), shrunk the pictures down to postage stamp sizes and swapped locations of the last two images!

If there's confusion, this one is supposed to be the "angled cuts on two of the pieces" image:
Attachment 685555


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