Some people's speakers/headphones might not actually be producing >16KHz depending on the quality and configuration of your setup.
My hearing is a bit odd - I can still hear 19-20KHz at 34 though only just but some intermediate frequencies i.e. 17KHz have entirely gone - probably due to exposure to high levels of sound from a mixture of work and nights out.
I've got a decent Mid-Fi setup I think.
Currently using my SoundMAGIC HP200's 'phones running from a Xonar DX and powered by a Fiio A3 amp.
Might try with my DT990's later, they're upstairs at the moment, and I'm idle
