All Grado headphones have a vented diaphragm design that incorporates a large air chamber. This design concept lowers the frequency resonance (distortion) of the diaphragm and extends bass response. The diaphragm is made of a low mass polymer, carefully formed to broaden resonant modes to reduce their amplitude. The diaphragm mass is determined with the compliance of the suspension in mind so that the desired low frequency resonance is achieved. The diaphragm's total mass is calculated to provide a full 20 KHZ bandwidth, while avoiding break-up at lower frequencies.
The Professional, Statement, Reference Series and along with the Prestige Series SR325is, SR225i and SR125i feature voice-coils that are wound from ultra-high purity, long crystal (UHPLC) oxygen free copper. The copper is slowly drawn through the die in extremely small increments and is annealed following each drawing operation. Ultra-high conductivity copper yields the clearest transmission and lowest coloration possible. The sound of UHPLC copper is smoother, cleaner and more dynamic. All use very high power neodymium magnets to provide maximum efficiency and better sound. Each headphone driver is made to Grado's high standards, then pair-matched for exact imaging. These headphones also utilize UHPLC copper in the connecting cable.
All metal work for the PS1000 and SR325is is machined from a special non-resonant, very hard alloy. Grado utilizes a special processing method to increase the material's porosity. This complex treatment insures that the earphone chamber has no "ringing" which might obscure detail or add coloration.