Did you know that stereo headphones for personal music listening, were invented right here in Wisconsin? In 1958, John C. Koss, and engineer Martin Lange, Jr. invented the Koss SP/3, as an accessory to a new stereo portable record player. The headphones were a smash hit, and proved more popular than the record player! If … Continue reading Koss Pro4/AA Headphones resto-modded into great DJ Headphones!