I followed this eartip rolling instructions http://www.head-fi.org/products/nuforce-primo-8/reviews/11187#comments-title and fitted the Primo 8 with a combination of the smallest tips + JVC Spiral tips.... The sound did improve but I either must have unusual ear canals or I got spoiled by by my other cans of HD650, PM3, H6, THX-00, ... Fitting is definitely a factor as if I pressed against my ears to get a tighter seal, it improves again. However the Primo SQ is still not natural, it sounded "off". I only had about a hour so I will try to burn them in longer unattended. I also have a few other amps including tubes to try but those impediances are not right for IEM. The adventure continues to correct my own operator errors or compensate my ear canal defects.