The legendary Koss Pro4AA – full-range studio sound with serious isolation. Koss introduced the Pro4AA in 1970 as the first dynamic headphones with true full-frequency, high-fidelity performance. They are full-size professional headphones for broadcast and recording, brought back by Koss after strong demand.
Why customers choose it
Who it is for
Recording and broadcast engineers, audiophiles with headphone amplifiers, and collectors of classic Koss headphones.
Specifications
| Type | Full-size, closed, dynamic |
|---|---|
| Frequency response | 10 – 25,000 Hz |
| Impedance | 250 ohm |
| Sensitivity | 95 dB SPL/1 mW |
| Distortion | Under 0.1% |
| Cord | 8 ft coiled, single entry |
| Plug | 6.3 mm (1/4-inch) |
| Connectivity | 6.3 mm plug |
Good to know
- This is an open-box unit of the product described here.
- 250 ohm headphones sound best from a studio interface, mixer or headphone amplifier; phones may not drive them loud.
- Phones need a 6.3 mm to 3.5 mm adapter.
FAQ
Can I use it with my phone?
It has a 6.3 mm plug and 250 ohm impedance, so it is best with studio gear or a headphone amp.




































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