1. A textile processing assembly for texturing and heatsetting a moving length of ply-twisted yarn, said textile processing assembly comprising:(a) a pair of feed rolls adapted for engaging and moving the yarn downstream away from a supply creel;
(b) a textile stuffer box downstream of said feed rolls, and comprising:
(i) a housing assembly having a yarn entrance and a yarn exit, and comprising cooperating chamber-forming surfaces defining a multi-stage internal crimping chamber for receiving and accumulating the ply-twisted yarn between the entrance and exit of said housing assembly, said crimping chamber comprising an upstream fixed-volume stage and a downstream adjustable-volume stage;
(ii) means for selectively adjusting a volume of the downstream adjustable-volume stage of said crimping chamber, thereby controlling axial compression of yarn accumulating inside the upstream fixed-volume stage of said crimping chamber, wherein said means for selectively adjusting a volume of the downstream adjustable-volume stage of said crimping chamber comprises an elongated chamber gate extending linearly between opposing terminal end edges and a removable gate weight, said chamber gate being pivotably mounted to said housing assembly at an intermediate fulcrum point of said chamber gate, and said fulcrum point dividing said chamber gate to form an inside-the-chamber first end defining at least one of said chamber-forming surfaces adjacent the yarn exit of said housing assembly, and an outside-the-chamber second end comprising a removable gate weight, and said first and second ends of said chamber gate being integrally formed together as a single elongated structure, and said gate weight being selectively positioned along the outside-the-chamber second end of said chamber gate to adjustably increase and decrease a resistance exerted by said chamber gate, whereby selective adjustment of the gate resistance operates to control axial compression of yarn accumulating inside of said crimping chamber;
(c) a climate chamber downstream of said stuffer box, and adapted for heat-setting the ply-twisted yarn;
(d) means for conveying the yarn downstream from said stuffer box and through said climate chamber; and
(e) a take-up winder downstream of said climate chamber for collecting the processed yarn.