7. What are the differences between the 2 sizes of sound tubes? And how to change it?

The FD3 comes with 2 interchangeable sound tubes. While the outer diameter of the sound tube remains the same, the inner diameter differs for each sound tube.
The red small inner diameter tube (preinstalled on the FD3): balanced tuning with soft sounds.
The black large inner diameter tube (included in accessories):higher resolution in high frequencies.

[How to change the sound tube]