Abstract: Processes and apparatus are provided whereby the morphology of bulked continuous filament (BCF) yarns can be variably controlled. More specifically, according to the present invention, the BCF yarn is melt-spun, drawn and textured, most preferably in a one-step spin-draw-texture (SDT) process, wherein prior to texturing, the yarn is subjected to a differential temperature condition. Most preferably, such differential temperature condition is accomplished using the duo rolls employed in drawing the BCF, such that one of the rolls is maintained at a greater temperature as compared to the other of the rolls. Most preferably, it is the upstream-most roll (relative to the general conveyance path of the filament toward the texturizer) which is the hotter of the duo rolls.