Luckily for all, the firmware is optional, so for anyone having strong opinions before even trying it, they can relax and continue their way. It just so happens that so many people heard changes even just from a firmware version to another, especially when it comes for the Sony OS players.
Sound changes also must always be frequency response related, there is no other way that sound can be altered.
I must be fooling everyone I guess, appealing to their self deceipt inclination. It's not like if anyone from Sony would admit that they can do this, that Sony won't be judged for it by consumers.
#BadMrWalkman
I won't continue this thread of discussion, there is no end with you anyway. Have fun.