I think Ativ S sound speaker isn't specially louder. Not bad either. The quality of it is quite good for a phone however... It may be limited by software to protect it. Or you may need to clean the speaker, I had to do it once. Since the speaker is magnetic, it attracts tiny metal dirt which affects the sound over the time. Cleaning it isn't very hard check in YouTube how to access it. In summary you have to remove the back, remove the sim, microsd and unscrew every screw you can see on the back, then remove the lateral bezzel previously heating it with a domestic heater (The same you use for ur hair works). I think this should be do at least once a year to clean the whole phone. Mine got the charging port broken and I had to replace it. I think it was due to the accumulation of conductive dirt.
Sry for my english.