Need a built-in ROOT!

1. Install any Root Explorer.
2. Go to the path / system / etc / There we find a file called mixer_paths_wcd9326.xml. Long tap on the file - open it in the Explorer text editor. Find the line <ctl name = "RX HPH Mode" value = "CLS_H_LP"/>
We edit it to look like this: <ctl name = "RX HPH Mode" value = "CLS_H_HIFI"/>
We do the same in the file mixer_paths_wcd9335.xml.
3. Now we are looking for files named mixer_paths.xml and mixer_paths_mtp.xml in them. Edit the line < name = "RX HPH Mode" value = "NORMAL" />  To look like this <ctl name = "RX HPH Mode" value = "HIFI "/>
4. Do not forget to save changes before exiting from editing. We save.  5. Reboot the phone.
The sound will be more "deep" and with good bass.