Since creation of F-15 we have always been thinking about all possible upgrades, after years of development and experiment, we can now proudly present to you Fast-15, a new member of Fast series. This model is optimized in detail and soundstage, giving a more present imaging and fuller sound body. The bass is deeper and more elastic that the energy can be released and pulled back quickly and easily. This model also has high end extension that rolls off up to 18kHz, giving a more vivid and swift sound experience. It uses the same basket as F-15 and can be direct upgrade by replacing the driver unit.