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Multi-Way Conventional loudspeakers with crossovers

Open source Waveguides for CNC & 3D printing!
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Old 8th June 2018, 10:35 AM   #101
jzagaja is offline jzagaja  Poland
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Open source Waveguides for CNC & 3D printing!
Ask winbocn03 on Skype, they want 65$ per waveguide plus shipping.
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Old 8th June 2018, 11:06 AM   #102
jazbo8 is offline jazbo8
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Will do, thanks.
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Old 24th August 2018, 04:44 AM   #103
augerpro is offline augerpro  United States
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Update! I'll post results over the next few days as I progress. This post will be all SB Acoustics: SB26ADC, SB21SDC, and SB29SDAC. I also will have results for the CSS LD22, Dayton RST28 A & F, and SB19ST over the next few days.

Couple reminders, all of these have elliptical mouths. Measurement conditions are MLS with 7ms of reflection free signal, NO smoothing. The spikes you see around 24khz are artifacts of the sound card cutoff causing some crazy FFT math. This isn't my old monster baffle, so baffle effects start to show around 3khz and below. The most obvious sign is the waviness of response and ripples and dips that flip around according to angle. Anechoic response would be smoother and SPL would drop as you move off axis.

First up, version G for the SB26:
zd1kTeC.png ozyO0pC.png

I would say we're done here, but for the heck of it I designed one with an oval throat, vertically aligned. I don't have measurements yet of that.

Unless you can design a phase plug similar to a compression driver, the key to a smooth top octave is to make the throat small, the closer you can get to an inch or so the better. That is why I was excited to see SB's new 21mm tweeter with fabric dome (no phase shield needed) and copper shorting ring! Results were very satisfying:

noc1atP.jpg emRdPeM.png Ad1aN7m.png SurE12q.png

I have one last waveguide to test with SB19ST but with the above results and the fact that the SB21 has a shorting ring, makes me think spending more time on the SB19ST is unneeded.

Next is the big fabric dome SB29SADC. I reused the 8" waveguide from the TW29 tests I did. The SB29 looks a lot better, but still that big throat causes some issue. Still the directivity would probably match an 8" woofer well 1-1.5khz and you would have a smooth upper midrange and lower treble.

VEzfO1x.png
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Last edited by augerpro; 24th August 2018 at 04:46 AM.
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Old 24th August 2018, 06:56 AM   #104
Mawes is offline Mawes
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Very nicely done Augerpro. I bet you spent many hours on this project. Would you mind posting screen of G-version 0, 30, 40 and 50 degrees with 50dB scale?

Are the wg-drawings public?
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Old 24th August 2018, 04:01 PM   #105
augerpro is offline augerpro  United States
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Here is the .stl: Dropbox - 5x.75 G SB26 v5.stl

Here is the scale in 3db divisions:

Click the image to open in full size.
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Old 24th August 2018, 08:33 PM   #106
augerpro is offline augerpro  United States
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Today's update. First up the CSS LD22. When I was given the throat diameter I knew there would be top octave trouble, and this is exactly what we see. The good news is now that I have this in hand, I can tighten up the throat quite a bit, at least to 1.31" used in version G of the SB26 guide which is looking quite good now.

Click the image to open in full size.

Next is the new Dayton RST28A and F. Lot's more to experiment with: using the standard faceplate the throat is huge, and I have my doubts about the phase shield being so far away from the diaphragm. Improvements in both areas in future versions.

Click the image to open in full size.
Click the image to open in full size.

Up next is the SB26 version G, but I made the throat slightly oval. Imagine it being about a 3/32" longer in the vertical dimension. Forgot to do no phase shield measurements.

Click the image to open in full size.

Earlier in my experiments I played with phase shield shape and size. Eventually settled on a round .25" diameter phase shield. But since those waveguides were so different -all were circular mouths- I thought I'd revisit phase shields to see if the earlier results held with these current, more optimized, designs.

Click the image to open in full size.

And last, the SB26 version G with no phase shield (and with and without a shim at the throat):

Click the image to open in full size.
Click the image to open in full size.

6" and 8" guides for SB26 and RST28 coming soon.
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Last edited by augerpro; 24th August 2018 at 08:35 PM.
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Old 24th August 2018, 10:47 PM   #107
Gaga is offline Gaga  Europe
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Thanks for the update and for posting all these measurements - very interesting!

I just realized, that some images I posted earlier are barely readable after resizing (e.g. post #80). As you are still evaluating the impact of adding a 'step' or 'shim' at the WG throat, I add one image showing simulations of a WG (V2, VarC-related) with steps (or shims) from 0mm to 5mm.


Open source Waveguides for CNC & 3D printing!-wg-0-5mm-step-jpg
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Old 25th August 2018, 01:03 AM   #108
augerpro is offline augerpro  United States
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Quote:
Originally Posted by Gaga View Post
As you are still evaluating the impact of adding a 'step' or 'shim' at the WG throat, I add one image showing simulations of a WG (V2, VarC-related) with steps (or shims) from 0mm to 5mm.

Yep, I've noted when I use shims in the plots. Most of the designs include about .015" to get a good seal, IIRC. So the shims noted would add to that.
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Old 25th August 2018, 05:59 AM   #109
jazbo8 is offline jazbo8
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Quote:
Originally Posted by Gaga View Post
I just realized, that some images I posted earlier are barely readable after resizing (e.g. post #80). <snip>

Click the image to open in full size.
In fact, this image does not resize properly, where as the earlier one does. Which browser are you using?
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Old 25th August 2018, 07:02 AM   #110
Mawes is offline Mawes
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Originally Posted by augerpro View Post
Thank you, much appriciated
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