High Quality Sound Sets Performance Standard for Portable Listening First introduced in 1984, this high quality portable stereophone set performance and comfort standards for personal listening worldwide. Over the years, much to the delight of devout Porta Pro enthusiasts, we’ve preserved the original design and performance that made the Porta Pro a portable music icon. Today the Porta Pro remains the headphone of choice for the discriminating listener. Designed for those with refined musical acuity, the Porta Pro continues to be the most requested headphone at koss.com. The Porta Pro features dynamic elements that deliver exceptionally rich, deep bass and a remarkably wide frequency response from 15-25,000 Hz to capture every nuance in your favorite movie or musical performance. Constructed from mylar, the elements are extremely rigid, minimizing mechanical distortion and ensuring exceedingly accurate sound reproduction. Neodymium iron boron rare earth magnet structures enable the Porta Pro to deliver greater volume so you can hear every note, even when competing against the sounds of a commuter train with a low-voltage MP3 or disc player. Oxygen free copper voice coils improve signal transmission and conduction for cleaner, clearer sound. Foam earcushions provide an open, hear-through sound that lets you keep in touch with your surroundings perfect to wear while running, at work, or while traveling. Whether you’re listening at home or on the go, the Porta Pro will bring the excitement of a live performance to any recording. The PortaPro by Koss is covered by Koss' No*Questions*Asked Lifetime Warranty.