Take the high frequency test
I heard 18kHz, in fact at the ENT and audiologist's office I heard 19k. I was told I have the hearing of an 18 year old, btw I'm 60.
I have hyperacusis, which means I'm so sensitive to high frequencies that they can cause head pain.
That's why I need a HiFi rig to produce the true tone of an instrument with no distortion at the top-end. The trend to tip-up the highs on speaker designs and digital remasters makes it nearly impossible for me to listen to a bright system or many early digital recordings.
Attending live classical performances has not been a problem for me since higher register instruments are producing their natural timbre with an unlimited ceiling.
This is why I agree with
@georgehifi that a speaker needs to be designed to 20k and above. This allows accurate reproduction of the fundamental high frequencies plus the harmonics/overtones.
