The AK T9iE is the third in-ear collaboration product by beyerdynamic and Astell&Kern. Specially tuned for Astell&Kern portable music players, the AK T9iE has an extremely neutral sound signature with soft treble, linear midrange and slightly elevated bass.The AK T9iE uses beyerdynamic’s patented high-efficiency Tesla Technology and is manufactured by hand in Germany, satisfying the highest standards to make the sound more natural, especially when playing back hi-res audio. The newly designed acoustic vent port allows for improved bass response and enhanced treble softness by specially engineered two-layer acoustic filter with integral earwax protection.The newly designed acoustic vent port has a slightly enlarged vent hole that is located in the middle of the cover plate which allows for a very deep bass that is extremely well controlled. A specially engineered two-layer acoustic filter is utilized in the sound outlet, which serves two purposes – protection from earwax and an acoustic filter element which produces very pure and neutral treble.The cable is made with 4N pure silver with silver plated 7N OCC to deliver the high in this combination; and the 7N OCC to bring the low. This hybrid construction of pure silver, silver OCC and OCC litz creates a unique harmony with no more sharp highs or too much bass.The design of AK T9iE highlights the Contrast of Surfaces and shows the delicacy and details of Astell&Kern with jewel-like carved planes on the exterior housing. The illumination from the PVD coating will reveal different reflections of light so that you see various shapes depending on the viewpoint. It also has an ergonomic design that makes them comfortable to wear for many hours of music listening.