High-end equipment, usable only by high-end (and mostly young) humans.
Recently I bought a new amplifier. Much more recently I took a hearing test. If I had done the two in the opposite order, I would not have wasted over Rs.40,000 on an amplifier which, according to the rules of audiophilia, has, of course, no tone controls.
Even those with perfect hearing do not necessarily listen in perfect rooms.