Koss

Explore 1 Koss vintage audio models — specs, production history, reviews, and market values in the VTA archive.

If you're talking about the birth of personal listening, you have to start with Koss. Before the SP/3 in 1958, headphones were utilitarian things for radio operators. John Koss, almost by accident, created the first true stereo headphones to demonstrate his portable phonograph. The moment people heard that spatial, immersive sound, the game changed. They didn't just sell a product; they created an entirely new category and a new way to experience music, which is their undeniable legacy.

The SP/3 started it all, but for collectors, the holy grails are the electrostatic models. The ESP-6 and later the ESP-9 were monumental. These were America's answer to Stax, complex, battery-powered beasts that offered breathtaking clarity. They proved Koss was a true innovator, not just a popularizer. Of course, the Pro/4 series became the workhorse, defining the sound of radio stations and home studios for a generation with their robust build and distinctive, warm character.

For a collector, condition is everything, especially with the vintage electrostats. Check for foam rot on the ear pads and headbands, and be aware that the original batteries for the ESP models are long gone, requiring some DIY ingenuity. The real thrill is finding a working pair. When you do, you're not just hearing history; you're hearing the ambitious, full-bodied sound that made high-fidelity personal.

Headphones

• ESP9 — Koss ESP9 electrostatic headphones with E-9 energizer, a 1970s American studio monitor featuring dual-power operation and fluid-filled cushions.
• KPH30i — On-ear wired headphones launched in 2017 as a modern retro-styled model with dynamic drivers and inline microphone
• KPH40 — On-ear wired headphones with detachable cord, part of Koss’s Utility Series and Retro Style Collection
• Porta Pro (1984) — An on-ear headphone introduced in 1984, known for its collapsible design and open-back dynamic drivers.
• PRO 4AA — Full-size wired stereo headphones introduced in 1970, designed for high-fidelity listening with a closed-back studio build.

Other Models

• Koss — Vintage Audio Equipment — Explore 1 Koss vintage audio models — specs, production history, reviews, and market values in the VTA archive.
• ESP-950 — An electrostatic headphone system introduced in 1990, built in the USA and marketed as the pinnacle of audio reproduction.
• ESP9 — Koss ESP9 electrostatic headphones with E-9 energizer, a 1970s American studio monitor featuring dual-power operation and fluid-filled cushions.
• HP/6 — A vintage on-ear headphone with in-line volume control, offered new in package and featuring replaceable orange foam cushions.
• K-6 — A twin-ear dynamic stereophone from Koss, developed and sold in the 1960s, part of the K series Slimline line.
• K/135 — A rare set of vintage over-ear stereo headphones from Koss, notable for their unique rectangular ear-pads with circular openings and coiled cable.
• K/7 — A rare on-ear dynamic stereophone from Koss, built for studio and live monitoring in the mid-1970s
• KPH30i — On-ear wired headphones launched in 2017 as a modern retro-styled model with dynamic drivers and inline microphone
• KPH40 — On-ear wired headphones with detachable cord, part of Koss’s Utility Series and Retro Style Collection
• Porta Pro (1984) — An on-ear headphone introduced in 1984, known for its collapsible design and open-back dynamic drivers.
• PRO 4AA — Full-size wired stereo headphones introduced in 1970, designed for high-fidelity listening with a closed-back studio build.
• PRO4AAA — A high-impedance dynamic headphone from Koss, notable for introducing the D-profile earcup design later used in modern models.