How to increase speaker/call volume? (cm11.2)
I'm thinking your phone is codenamed "evita" and the file you're looking at is here.  Maybe you could try kicking up those ":1:73"s to ":1:78" or another small increment, restart, and see if it's any louder.  If so, raise the number from 78 to 83 or whatever until you find the volume you like.

You can compare with this change for mako (Nexus 4) and this comment as well...  You might also Google for "msm8960 volume" to see recommendatiosn for other devices that use your qualcomm system-on-a-chip. 

I don't know for sure if this will work as expected, but you can report back and let me know if it does.