Share your experience!
The bass always disappears after plugging in my audio device into the earphone jack. I was given advice to start the phone in safe mode but it hasn't solved the problem. Restarting the phone normally only provides temporary relief then after a few seconds of playback the bass is gone
I suggest that you try to repair the phone software using PC Companion..
Before repairing your device you may want to backup your information first. Check out this topic for more information on how to.
How to backup?
If the issue should still remain I think that this needs to be examined and fixed at a repair center. For more information about how to submit your phone for repair and where, contact your local support team.
I have done the repaire and the problem still persists...
I think I found a solution to it... While the music plays unplug the audio jack and then plug it back in. It should help somewhat... But it is just the irritation of having to do that, still, just puts you off from listening to music entirely.
This didn't solve the problem
Hi there,
Same issue here on a Z1 C6903.
I think there's no use in contacting a repair center as the problem appeared since the lollipop Update.
It's some kind of software bug, not related to material at all.
All u can do is waiting and praying for sony to solve the issue in the next update.
Really, this phone was great when i bought it, but now I'm really disappointed by the "quality" of sony/google softwares.
I'm still fan, but magic is gone !!! 
So the 5.1 lollipop update hasnt fixed this issue yet...