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 that Koss Electronics Inc. developed and sold in the 1960s. It belongs to the K series and is categorized as a Slimline dynamic type. It goes by several names, including "Koss K/6," "K-6 LC," and "K-6 XLC," and it was also rebranded as the Realistic Custom Pros. These over-the-ear headphones were made in Japan and have a brown finish. Exact production years aren't confirmed. The model came out in the 1960s and stayed 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 replacement drivers, including 3D-printed driver mounts and removable cable modifications.

Context

The K-6 was part of Koss's early headphone lineup and is one of the company's foundational models from the 1960s. It was later rebadged and sold as the Realistic Custom Pros, so it turned up in both direct and retail consumer markets.

Market

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