On 3/19/20 2:09 PM, John Leonard Main wrote:
Hello chaps,
Hi,
(sorry, just now I get a minute to follow up on this)
As all my work has now been cancelled, thanks to Covid-19, I have time on my
hands and a new 3D printer to play with. I’d like to experiment with building a
couple of the SpHEAR microphones, but I can’t seem to work out how to download
the SCAD files so that I convert them to .STL format.
Has anyone done this? Got the files to share? Any info gratefully received.
I think it is clear from the rest of the thread, but just in case, this
would be the starting point:
https://cm-gitlab.stanford.edu/ambisonics/SpHEAR/
Thanks, and remember to wash your hands…
Doing that (and also working from home here in California).
...
Maybe this is all obvious, but just in case here it goes...
The _text_ in that git repository front page is _completely_ out of
date. I apologize. Always something more important to try to do, and
always swamped with too much stuff[*]. The three relevant papers I wrote
about this black hole for time are in my web site
(https://ccrma.stanford.edu/~nando/publications/).
However, the warnings in the git repository text that it is all an awful
amount of work are still true, and even more so for the eight capsule
design :-)
Which capsules do you have access to? While the design claims to be
parametric I have not actually tested that in a long time so this might
be a lie (the connectors between capsule holders in the v1 design are a
possible point of failure if parameters are not "reasonable").
For the 3d printing part of the project, the sequence would be, use
OpenSCAD to open the proper file, select which part you want to make and
render it to an stl file. After that it depends on the 3d printer you
have access to and what it wants, so far I have printed on Ultimaker
printers so I use Cura as as the "slicer" to create a gcode file which
is what those printers use.
The file "Octathingy_EM200.scad" would be the starting point for 14mm
capsules (EM200 from Primo). I think I have pushed all relevant changes
in my git to the master, let me know if you have problems. Depending on
the printer you may need to tweak some numbers ("fit" tolerances) so
that everything snaps together nicely and/or use a small file or Xacto
knife to deburr(sp?) edges (keep in mind I don't know how much
experience you have in 3d printing so maybe I'm saying things that are
obvious to you).
Different "parts" in that file are prefixed with a "*" which tells
OpenSCAD to ignore that whole section of code. So, remove one of those
"*"s, press F5 and you should get a pre-render of the chosen part (F6
does the final rendering from which you can export an stl file). I
believe this is all taken care in that file, but some parts are flipped
180 degrees with respect to their spatial orientation in the finished
microphone. I know, all very primitive.
More details that may impact the 3d print. There are two choices for the
printed circuit boards that house the phantom power interfaces, one,
bigger, single layer, but something I could make using a small mill we
have in the MaxLab (our small fabrication lab), the second one, smaller,
is double sided and I make them in short runs through a commercial
company. Both boards depend on specific components (detailed in a
spreadsheet) that match their dimensions and can fit in the body as
printed (electrolytic and mylar capacitors in particular) - the whole
thing squeezes together with not much room to spare.
Probably obvious again, but once you have the whole thing assembled and
wired you have to measure and calibrate it (but you knew that, of
course). Still working on the calibration part, I could use help with
that...
Did I mention it is an awful amount of work? :-)
I'm happy to help...
Best regards,
-- Fernando
[*] even "music", see videos here:
https://ccrma.stanford.edu/~nando/music/resurrections/
https://ccrma.stanford.edu/~nando/music/resurrections/video/
(binaural soundtrack captured from the center of the hall with one of
the Octathingys in 2nd order and rendered with the Resonance binaural
renderer...)
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