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.
• 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.
• ESP9 — Koss ESP9 electrostatic headphones with E-9 energizer, a 1970s American studio monitor featuring dual-power operation and fluid-filled cushions.
• 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.