You’re right- the mounting can have an impact on the amount of vibration imparted on to the flight controller with this setup. In order to make sure that the conditions are as close to identical between the tests, we would need to mount them all to the same plate at the same time.
I decided to run the tests again, but this time I mounted 2 flight controllers at a time to the speaker and compared the two (see pic). I bonded the flight controllers together to ensure there was no relative motion between them, so I think this is as close as possible I will be able to get to a direct comparison between flight controllers.
The tests I did were: Pixhack V3 vs. Pixhack V5+; Pixhack V3 vs. CubeBlack; Pixhack V3 vs CubeOrange. I compared all to the Pixhack V3 because a) it’s the best at removing low frequency vibrations and b) it was the easiest to mount to.
These are the results of those tests:
These results are largely in line with the original results I gathered and the experiences people have had with these flight controllers. As expected, the Pixhack V3 is again the clear winner. The Pixhack V5+ isn’t too bad either. The CubeBlack has a bad resonance at ~90Hz and the CubeOrange has a bad resonance somewhere between 60Hz and 90Hz. It’s worth noting that at higher frequencies the Cubes do much better.