Of course normal computer headphones or speakers aren't a great test for this, since their frequency response rarely goes that high. Especially the samples >20k

Of course normal computer headphones or speakers aren't a great test for this, since their frequency response rarely goes that high. Especially the samples >20kHz, since that's beyond the normal range of human hearing. Even high-quality headphones won't play high-frequency sounds, the -3dB (half power) cutoff is generally about 20kHz. Having it higher can allow the headphones/speakers to produce unpleasant harmonics, so good devices are built to damp out such high-frequency resonances.