Koss KRD-711

Not much is documented about the Koss KRD-711 beyond what Koss itself said in 1971 advertising. It was a lightweight headphone, sold as the "Red Devil" - a "little devil" that delivered the exciting sound of Koss with uncommon range and clarity. An ad in High Fidelity (May 1971, p.11) gave the frequency range as 10-20,000 Hz and the weight as 12 ounces.

Koss's trade ads in 1971 pitched the KRD-711 for studio applications, at $29.95. They claimed it was comfortable, practically blowout-proof, and presented no impedance matching problems. That's about all the surviving record gives us.

- Weight: 12 oz

- Frequency range: 10–20,000 Hz (manufacturer claim)

- Price: $29.95 (1971)

- Marketing nickname: "Red Devil"

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