Enter code *#0523#
Press the key '#' several times until you get a menu.
Press volume-down button to go to next menu page until you get a menu where you have the option:
[3] SPK Config
Pres '3' key
I suppose it should be done here but no idea witch one of the offered params is what you need.
Good luck and post your results!
NOTE:
See you have an option:
[2] Dump Params
If you use it you get this message:
A dumped file is
/SystemFS/Driver/
SPK_Data_Load.txt
>>> Dumping complete
No idea what that file has but you can get it using BitPim utility + Qualcomm USB driver