This is a set of quad driver custom IEMs that I recently completed for a friend of mine. Drivers used are a Knowles GVs. If you're interested in a DIY, I'd be
DIY dual drivers clear sound extra bass HiFi In-Ear Headphones IEM for monitor | eBay
DIY upgrade clear sound extra bass HiFi In-Ear Headphones IEM for monitor | eBay
DIY custom in ear monitors - how to build custom in ears - uv resin - english subtitles - YouTube