[Entlin]

Exactly, many people cannot differentiate front/back and up/down with general purpose HRTF, something that is much better with a custom HRTF.

For basic experiments, put 2 small microphones into your ear canals, hit record, then go for a walk. The result will blow you away :-)

To record your custom HRTF, get an anechoic chamber, put 2 small microphones into your ear canals, then record impulse responses from all directions. Not quite as simple.

Good luck! Post your results here!