An end fastener for attaching an end of an eyeglass retainer to the end of an eyeglass temple piece includes an elastomeric fastener body secured to the retainer cord or rope and having an internal bore extending into the body from an insertion opening. The thermoplastic material containing silicone exhibits good thermal stability, and resists build-up in the nozzle of an extrusion head or jetting head of a three-dimensional modeling apparatus. A control section controls the sound signal processing operation of the sound signal processing module based on the operation data set stored in the current memory. Each seat is contoured downwardly forming a seat depression. Here, it is provided that a control for the input signal correction and a control of the cylinder equalization are activated alternatively by an alternative circuit unit.