The new pro4aaat follows in a long line of koss stereophones designed for the broadcast professional the latest titanium version features a sound of koss that every discriminating listener is sure to enjoy the pro4aaat features titanium coating on 2 mil mylar diaphragms for a frequency response of 10 25 000 hz oxygen free copper voice coils improve signal transmission and conduction for accurate sound computer optimized ferrite magnet structures provide deep bass and treble clarity closed