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augerpro 30th January 2018 08:44 PM

Open source Waveguides for CNC & 3D printing!
 
6 Attachment(s)
I've been working on a waveguide project where I would develop high performance waveguides for some popular tweeters, and than share the files for anyone to print or CNC as they are able. The discussion started here: 3D printed waveguides - Techtalk Speaker Building, Audio, Video Discussion Forum for more details. The short summary is starting with the SB26ADC and a 5" waveguide, I varied flare radius, phase shields, depths, etc. I've started to find some best practices (at least with this dome/horn combo) and all future guides will have elliptical mouths, and with and without phase shields. I then skipped to 8" designs to verify those best practices scale, so anything in between should be trivial to design and still have the expected performance. Tweeters that I'm currently designing for are: SBA SB26ADC, SBA SB19ST, Satori TW29RN, and Transducer Labs N26C-A.

To get some frame of reference, here measurements of the Kef Reference 5 prototype, and Revel Concerta2 (which I suspect also uses the SB26ADC):

Attachment 672999

Attachment 673000

Here is my "C" waveguide with SB26ADC, with and without phase shield:

Attachment 673001

Attachment 673002

Quite good results I think, better than Revel achieved with the same tweeter! Anyway, the reason I am posting now though this project is still in its infancy, is I've connected with a couple gentleman with the ability to model waveguides. This could speed things up considerably, as waveguide design is extremely iterative otherwise because 90% of the performance happens at the dome/throat interface and this is not easily modeled.

We've started with verifying that the sim can accurately predict reality. With as close a representation as possible of the dome here are the results:

Attachment 673003

Attachment 673004

Extremely encouraging! I'd like to do some additional verification - particularly of the 8" guides I've started working on - and then I hope to push the sims to the max, and start producing some really excellent guides for popular tweeters.

augerpro 30th January 2018 08:49 PM

BTW I should add some background on measurement conditions. I use MLS signal with a 6ms gate to remove the first reflections. Measurements were at 1.5m or so, with a calibrated mic. The baffle was not the big baffle I used for measurements at my drivervault site, but 2'-ish by 3'-ish rectangle with the driver offset. Sim showed quite smooth response to about 1khz, but I suspect diffraction is starting to creep into the measurements <4khz and are significant closer to 1khz. Angles are 0-60 in 10 degree increments.

augerpro 30th January 2018 08:54 PM

2 Attachment(s)
Some examples (the mouths are round to facilitate easy mounting on my baffle with just a circle cutout, actual print files are elliptical flanges):

mlee 30th January 2018 09:03 PM

Fantastic work! Those guides look great too, are they 3D printed? This is a great concept, subscribed even though I doubt I have anything to contribute. I do have access to a 3D printer so maybe I could do some testing if required. Best of luck!

augerpro 30th January 2018 09:10 PM

Yes they are printed via laser-sintered nylon. Resolution is excellent and the strength is fantastic. Hard to photo though.

Rokytheman 31st January 2018 11:45 AM

Very interesting. Keep us opdated :-)

Would really like to try a waveguide with one of the SB tweeters.

S4m 31st January 2018 12:57 PM

Wow! As Roky said, very interesting :)

fatmarley 31st January 2018 01:21 PM

Cool project and very kind of you to share the files.

jcarr 31st January 2018 01:55 PM

Kudos for a project that could be very useful for many!

Zonneschimmel 31st January 2018 05:21 PM

Subscribed. I have a pair of 26ADC and Satori TW29RN and some friends with 3D printers :-).

Not sure if possible but I would be very interested in (and even pondered trying to sim it myself) a Seas DXT type waveguide.


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