Koss K/7 (1975)

Name: Koss K/7
Brand: Koss

A rare on-ear dynamic stereophone from Koss, built for studio and live monitoring in the mid-1970s

Overview

The Koss K/7 is a dynamic stereo headphone released in 1975. It was sold under several similar names, including "Koss K-7" and "Koss K/7 K7 Dynamic Stereophone." Koss designed it for professional use: DJ work, live monitoring and studio monitoring. It is an on-ear design with a double housing, and it was originally offered in beige. Documentation is thin. Surviving units are labeled rare vintage items, and some have turned up in mint condition with the original packaging.

Specifications

Frequency Response	10Hz - 18,000Hz
Impedance	100 ohms at 1kHz
Weight	425gms
Total Harmonic Distortion	less than 1% at 1kHz, 100dB-SPL
Driver type	Moving coil stereo headphones
Color	beige
Model / part number	model K7, P/N 13-3714, F/N 74
Suitable for	DJ, Live Monitoring, Studio Monitoring

Design

The K/7 is an on-ear design with a double housing. That suggests the aim was isolation and a rigid structure for monitoring use.

Context

The K/7 came out in 1975. It belongs to a generation of professional-grade headphones built for durability and accurate audio reproduction in live and studio environments.

Market

Listings from 2025 show Koss K/7 units selling for $40.00 on Mercari, $88 on Facebook Marketplace (Citrus Heights, CA), and C$41.51 on picclick.ca. One was described as fully working and in mint condition with original box.