I tried the music playback from my Fenix 5X+ and compared it with:
- cable playback from an iPhone6S on Shure E5c and Westone UM2 headphones.
- BT playback from the same iPhone6S and from the 5X+ with a Griffin BT adapter on the Shure E5c and Westone UM2 headphone.
- BT playback from the iPhone6S and 5X+ on a Naim Mu-So Qb.
The sound quality from the Fenix 5X+ is in all cases lower and not really good.
Since the sound quality from the 5X+ is worse for all playback devices, I think that the problem comes from the 5X+ and not from the Griffin BT adapter (the older Shure E5c and Westone UM2 do not have removable cables like the current Shure SE535 and Westone UM 20 pro and aren't compatible with the Shure or Westone BT adapters).
What are your experience with the Fenix 5X+ music playback quality compared to some other source devices ?