Koss K-6 (1960s)

A twin-ear dynamic stereophone from Koss, developed and sold in the 1960s, part of the K series Slimline line.

Overview

The Koss K-6 is a dynamic stereo headphone developed and sold in the 1960s by Koss Electronics Inc. It belongs to the K series, categorized as a Slimline dynamic type. Known by various names including "Koss K/6," "K-6 LC," and "K-6 XLC," it was also rebranded as the Realistic Custom Pros. These over-the-ear headphones were made in Japan and feature a brown color finish. While exact production years are not confirmed, the model was introduced during the 1960s and remained in circulation into the 1970s.

Specifications

Product type	Stereophones (headphones)
Frequency Response	10-16000 Hz
Power handling	60 watts per channel
Driver Size	89mm - 3.5''
Weight	516 grams
Original price	$26.50 (source unconfirmed)
Country of manufacture	Made in Japan

Design

The K-6 is an over-the-ear dynamic stereo headphone. Some units have been restored with rewiring and modern driver replacements, including 3D-printed driver mounts and removable cable modifications.

Context

The K-6 was part of Koss's early lineup of headphones and represents one of the company's foundational models from the 1960s. It was later rebadged and sold as the Realistic Custom Pros, indicating its presence in both direct and retail consumer markets.

Market

Units have been listed for $25 to $45 in recent sales. Some units appear non-functional after long-term use, with reports of failure after approximately seven years of ownership. Restoration efforts include rewiring and component upgrades.