Koss has introduced the A/550, a new over-ear headphone model that brings an open-back design to the company’s mid-range Auditor series. With a weight of just 10.1 ounces (287 grams), the headphones are built to deliver a wide, spacious soundstage while remaining comfortable over long listening sessions. The design also accommodates balanced audio connections through a user-swappable mini-XLR cable system.
Asymmetrical Design and Materials
The A/550 carries forward the series’ hallmark: an asymmetrical ear cup shape engineered to enhance stereo imaging and overall sonic transparency. Each open-back earcup is fitted with magnetically attached, ultra-soft cushions covered in breathable velour, while the headband uses an auto-adjusting sling wrapped in vegan leather. Koss describes the tuning as a balance between revealing fine detail and maintaining a smooth tonal character suited for relaxed, fatigue-free listening.
Internal Components and Connectivity
Inside the ear cups, multilayer polycarbonate diaphragms drive a frequency response spanning from 12 Hz to 22 kHz. The impedance is rated at 54 ohms, with a sound pressure level of 92 dB. For out-of-the-box use, a 6.5-foot (2-meter) mini-XLR-to-3.5 mm cable is included, along with a 3.5 mm-to-6.3 mm adapter for broader compatibility with traditional unbalanced outputs. Users who prefer a balanced audio path can supply their own optional cables via the mini-XLR connector on the headphones.
Company Legacy and Market Position
Koss has deep roots in personal audio history, having manufactured the SP/3 in 1958, widely recognized as the world’s first stereo headphones. The brand has since maintained a visible presence with enduring designs like the ultra-light Porta Pro, which has achieved cult status among portable hi-fi enthusiasts. The A/550 arrives as the latest hi-fi model in the Auditor range, aimed at listeners seeking open-back acoustics and flexible wired connectivity at a mid-level price.