Microphone selection for belt tuning app  

Microphone selection for belt tuning app

I was becoming frustrated with my Core One + kit after it passed all self-tests and printed the keychain but had issues when printing the calibration cube in vase mode. I tuned the belts fairly close with the phone app, then used the built-in manual belt tuning. It didn't seem very precise as the oscillation spread over 6 Hz or more with the manual belt tuning. After much effort and many support chats investigating pulley tightness, gantry squareness, etc. I discovered that the phone app used my hearing aids as the microphone source. Hearing aids have basically no low frequency response, so the phone app wasn't reliable at all. In fact, what the phone app detected was the 2nd harmonic, which I dutifully adjusted to 96Hz.  What I saw with the built-in manual tuner was also a 2nd harmonic. Finally, when I was setting the belt tension for the 20th time, it occurred to me that I needed to turn off the hearing aids so the phone app would listen to the microphone in the phone that I positioned near the belt. 

What do you know, you really need to tighten those belt tension adjusting screws. They push back by the time you get to 96 Hz. And the manual belt tuner is super easy to see and very precise once you stop detecting 2nd harmonics. 

The ridges on the left are nearly gone when reprinting the calibration cube and I'm moving on to print other more interesting objects.

Cube printed in vase mode