Sennheiser IE 900 Audiophile in-Ear Monitors – TrueResponse Transducers with X3R
What refines the X3R technology is its three Helmholtz resonator chambers and acoustic vortex which smoothens masking resonance. The three resonator chambers are precision-drilled into the elegant aluminum chassis of the IE 900 and placed between the diaphragm and the nozzle.