On 09/17/2016 11:24 AM, Bo-Erik Sandholm wrote:
Octathingy is probably 2 Tetra mics joined so we have
Front Left Up, front left down, front right up, front right down
Back Left Up, Back Left Down, Back Right Up, Back Right Down.

I think it can be called a second order mic, i believe it was presented at
aes a few years ago...
It is designed by 2 of our veterans from sursound, but my memory fails me
at this moment ,:-)

Eric Benjamin and Aaron Heller (they have been incredibly helpful and supportive!), and yes, 2nd order horizontal and better first order overall, can't wait to test drive it (I was doing the full design for a real one including the housing for the interface electronics two weeks ago)... See attached "picture" (the capsule assembly is pushed into the slots in the mount)...

-- Fernando


On 17 Sep 2016 19:56, "Stefan Schreiber" <st...@mail.telepac.pt> wrote:

Fernando Lopez-Lezcano wrote:

Hi all,

I've been working on this project since November 2015, and at the time I
thought I would be done by Christmas, hence the subject line... (I was very
naive). The main motivation of the project was to have easy to build and
cheap microphone arrays for my students to use in class (@ CCRMA,
Stanford)...

So, you can choose what you can use this for: Ambisonics themed Xmas tree
ornaments, 3d puzzles of platonic solids, big earrings for your loved ones
or, perhaps, microphone arrays.

I've been working on designs that are 3D printable as flat pieces on
cheap or medium priced printers and are assembled and glued together like
3d puzzles, starting with a regular tetrahedral first order microphone and
then moving on to Eric Benjamin and Aaron Heller's Octathingy (8 capsules)
and a few more "platonic solid" designs (12 and 20 capsules, these last
just to test the concept of even bigger 3d puzzles - it works).



It is a bit frustrating to read about (probably)  interesting projects
which are< completely unintroduced >.

https://ccrma.stanford.edu/search/node/Octathingy

Didn't find any real info. Is this supposed to be some 2D design? If so,
Orange Research Labs also had some prototype, and also some 12-capsule (2nd
order-3D) prototype but which seems to be to big. (Capsule distances on
sphere implied an spatial aliasing limit of about 4.5kHz, which would be
(too) low for any serious recording.)

So, < before > talking about 3D printed holders: What actually IS an
8-capsule Octathingy?

Waiting for some enlightening infos...     :-)

Best

Stefan



All models are written in Openscad (a 3d modeling programming language),
with most of the dimensions being parametric - the models are, after all,
just software.


What does this mean? "Parametric dimensions" for some 3D printer???

I spent a couple of weeks doing plain old geometry on paper to try to get
everything to fit just right...

I wrote a paper on the progress of the project so far for AES SFC (which
I regretfully was unable to attend), you can find it for now in my web page
- jump to the publications link[*]. I have a first working prototype
(calibration and measurements in the paper), I'm currently working on two
more and looking forward to testing the 8 capsule design.

A lot of work ahead (coding and hardware design, documentation, etc).
This turned out of be a black hole for any time I can throw at it.
Contributions welcome...

GPL Openscad code and Creative Commons licensed 3D models are available
here:

   https://cm-gitlab.stanford.edu/ambisonics/SpHEAR/

(there is also a low volume mailing list available, so far 0 messages :-)

You can also find a Kicad PCB design for the phantom power interface for
each capsule (they fit into the body of the latest design) and the
preliminary calibration software (GPL, written in Octave) for the
tetrahedral design. But of course everything needs better documentation.
Take a look, I included a few more pictures...

If you are tempted to build one be forewarned that it is a LOT of work :-)

Many in this list helped a lot (you know who you are, thanks!!), I would
not have gotten this far by walking alone.

Enjoy!
-- Fernando

[*] https://ccrma.stanford.edu/~nando/

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