I wanted to ask a general question about isolation and CIEMs. I had a bad experience previously with CIEMs. They were hollow acrylic and the fit was fine, but they only extend to about the first bend of ear canal. The isolation was disappointing (worse than some of my universals). The audiologist is one who is recommended by JH Audio, Noble Audio etc and the ear impressions he taken extended to the second bend. Well, the company would not do a refit, because they said they do not make the canals to the second bend for reasons of comfort.
So my question is that provided the impressions are good and the fit is correct, which provides better isolation - hollow acrylic shells that have long canals (say to the 2nd bend) or shorter canals but with filled acrylic shells? I’m trying to pick a CIEM and if the sound signature is more or less the same, the best isolation would be the decider.