In developing the IE 900, we faced a fundamental choice. The inherent compromises multi-driver systems require (phase issues and the resulting distortion in overlapping frequency bands) made the decision easy. There would be a single dynamic driver only — of the highest quality, of course.
To get exactly the sound we were looking for, we designed a sophisticated system of three Helmholtz resonators — the X3R. It’s milled right into the solid aluminum housing of each earphone. These tiny channels eliminate resonance peaks which, in less advanced products, can color the sound signature and alter the feel of your music. In addition, a complex structure in the nozzle of each earphone — the Vortex — swirls acoustic energy in these frequency bands to smooth out peaks.