Headphones — Koss BT221i Bluetooth

The Koss BT221i is a wireless Bluetooth headphone built around pivoting ear-clips rather than a headband, a form aimed at active use. The clips pivot to find a secure fit and seal on each ear, and the housing is sweat resistant, so the set suits workouts and commuting as much as casual listening at a desk.

Key specs that matter

Connection is Bluetooth version 5.2, and the battery is rated for more than 18 hours of playback with USB-C charging. Sensitivity is quoted at 101 dB SPL at 1 kHz and 1 mW. The listed frequency response runs from 50 Hz to 18 kHz within 10 dB.

Engineering and use context

Buttons on the cable with a built-in microphone handle play and pause, volume up and down, and answer or end calls, so the phone can stay in a pocket. A cable management clip keeps the lead between the two earpieces tidy while moving.

Pairing

The BT221i links to a phone, tablet or laptop over Bluetooth, with no external amplifier or DAC required.