PhonoPhi
Headphoneus Supremus
No numbers, just some words - so typical."I started engineering calculation and experimentation, assuming at the beginning I could easily prove that skin effect could never affect sound quality. However, before long I was forced to realize that it was not so easy. In fact, I had to recognize the fact that sound is changed by cable, as a result of the very experiments by the discoverers in front of me, so that I was compelled to research it seriously. Skin effect is a part of eddy current nature, and although it is not possible to measure it at audio frequency range, it can be calculated electromagnetically and the calculated result can be verified by several methods. Therefore I did listening tests myself and asked many people for double blind tests, making many cable models that had different eddy current loss. These listening tests made me sure that skin effect has a rather large role in the sound differences." ~ Paragraph from Mogami's 2019 Catalogue, despite their rigorous measurements and technical backing
For IEM cables with few volts and milliamps (for few milliwatts total) - there are no any justification and no evidence for any effect in the audible range of 20-20,000 Hz.
But given that it is highly profitable to sell $100+ cables - many odd things are out there