I have always wondered how custom IEMs (including generic ones that share the same design philosophy) are tuned. Recording artists use them, so they must be really good. But how good? In order to be a good studio-monitoring headphone, a product must meet the ITU's criteria; However, I've never heard JHAudio, or Ultimate Ears mentioning anything about a flat diffuse-field. So I asked JHAudio:
"Are your IEMs made for a studio monitoring purpose, IOW flat-diffuse field referenced? Or just electrically linear?"
And I received an answer:
So it was the latter. No wonder Ultimate Triple.fi 10 pro's vocal range is receded. I'd like to thank JHAudio for taking time to answer my question.