DIY Spinorama Jig

[Toids_DIY_Audio]

I just found the one I was thinking of.

https://www.diyaudio.com/community/threads/automatic-polar-measurements-using-arta-stepper-motor-and-tic-controller.387325/

and here

http://nicholasmart.in/measurement_platform/

• This reply was modified 1 month, 2 weeks ago by  Toids_DIY_Audio.

diyaudio.com

Automatic Polar Measurements using ARTA, stepper motor and Tic Controller

I have been in the process of researching and preparing to build an automatic measurement table for a while as making a large number of measurements manually is no fun and very time consuming. I came across a great website … Continue reading

[TVOR-Ceasar]

When you think about it, the speaker should be rotated about the main vertical axis, and the combined Z axis, in order to keep the alignment as close as possible to the same distance from the mic. Therefore, a short front with a larger arc in the rear where the 10 degree notches can be placed, along with the latch to lock into those notches. I would do a foot activated latch, just a “L” you can step on to unlock. That’d save the back from excessive bending.

[Toids_DIY_Audio]

That is an interesting idea. I like that.vI also thought about just turning the volume knob up a little until it matched. That wouldn’t be too hard. The amount of volume adjusted shouldn’t really affect the response.

[TVOR-Ceasar]

Now that I think about it, wouldn’t it be easier to rotate the mic on it’s own degree arm? Maybe something like below.
Click description for main dimensions.

Make it as a sandwich, with the pivot between you could then put some felt on the top and bottom of the arcs, and thin plastic on the arm for ease of movement.plus, a 1/2 sheet of ply or MDF would be all that’s needed as you could cut all pieces, even spacers, from that one sheet.

[Toids_DIY_Audio]

This is the reason forums are so powerful! You’re absolutely right. It would be easier to just move the mic. It would be nice to table to allow the mics to be extended closer or further from the speaker. That way, depending on the size of the speaker, you could move it closer to remove more room reflections, if making measurements indoors.

I think I’m gonna try to make something up in the next week or two based off of your design. See if there’s anything that were missing or forgetting.

[TVOR-Ceasar]

Those 4 holes near the plunger are for some sort of mount – I envision a locking articulating arm for the mic, so it can go forward, backward, up, down, all in a straight line. They are just placeholders. The notches are 3/4″ wide, 1″ deep, with centers on the degrees marked. I figured the plunger could be a 3/4″ dowel with the last inch sanded down just enough to fit snugly.

I could do a lot more, get the Thickness set up, do the bottom piece, move the arm so it can be cut out, etc.

I have this in CAD as 2D for the moment. To Scale, 1″=1″ Not sure what type of file you can use. DXF? STL? EPS?

“”Edit- I just saw the 90 degree requirement. I could add the rest in and redo that.

Question – if you were to cut a 1/2 sheet on your CNC, cutting out the basic 24×36 shape, what would be left over? 23-1/2″? 23″? Just trying to get an idea for the bottom half of the “sandwich”.

[TVOR-Ceasar]

Have you thought about this any more? I have.

Taking into account all your previous requirements and thoughts on how things can be done, I have mentally designed an alternative to the semi-disc out front, and placing a disc underneath in the back with the V cuts on degree. Then, still using a long arm with the pivot at the front, like above, using a long dowel or similar with ramp cut /stop on the underside that a steel ball or marble.could ride in to protrude up into the V to hold the arm steady. Then, if you would need it, you could have a small semi-circle support out front, not solid, but open like a cheap student protractor, to give some additional support to the mic end of the arm. I don’t have time to sketch anytime up at the moment, so.i hope this is explanatory enough to get the idea across.

[TVOR-Ceasar]

I was working on a different version that would use the V-Carve. It was originally going to be an arc underneath, behind the pivot point, but I soon realized that the length of the arm both ahead and behind the pivot would weaken the platform that the speaker would rest upon. SO I reduced the arc out front to make the reflective area much less, and even cut out a semi circle inside to reduce the reflections even more. That semicircle and slight lip past the pivot point are where the V-cuts will be, all part of the actual top cover / speaker base. I got about 3/4 of the way through the arm before I had to stop designing for that session. I like the looks and style of this one a lot better.
The hard part is designing the mechanism. Vision and theory is all there. getting all the details just right, well, that’s the thing isn’t it. Good thing the materials (wood) isn’t that expensive.
You know, if the V-cut system doesn’t work out, a similar system to the first would work quite well, especially if you were to go with a slightly smaller dowel and cuts to accommodate the smaller radius.
After I get the Top views finished, then generic Side views and then onto the articulating arm.

**Yeah, my Dad was a mechanical drafting teacher who also worked summers in a local machine shop drafting design plans. Always had this stuff around, plus I draft Civil plans , etc. in my job. I guess it is in my nature.

[Toids_DIY_Audio]

That is another good idea. I am also working on a design. I am not sure exactly how it will work, but I am excited about it. Very similar to what you are doing. I do like the idea of moving the microphone and not the speaker, since the speaker is so heavy.

[TVOR-Ceasar]

This is my secondary thought. I like the looks of this one a bit better.

The main body from the 90° mark is 24″ x 24″, with lots of support underneath, yet enough room for the boom to turn freely from lock to lock (180°). The Diamond shapes would be on the bottom side to enable the locking of the boom at those points. I am evaluating whether it would be better to use something like this with a steel ball on a ramp system, or a plunger type of system with something like a 3/8″ dowel (up/down) plunger attached to a pivot/link, and if that would be the case, then a hole would be better than the diamond shape.

As you can see, the arc area is like the type of protractor you’d have used in school – open in the middle. Less reflective surface to deal with.

Choices, choices.