Наушники — Koss QZ99

The QZ99 from Koss is a closed over-the-head headphone on a cable that blocks outside noise by passive means alone. Koss states that it was first developed for people listening to racing radio scanners and for metal detector users, two groups that need to follow a weak signal against engine noise or outdoor wind. Its list price from the Milwaukee maker is USD 64.99, and the Koss Limited Lifetime Warranty covers it.

Key specs that matter

Frequency response on the QZ99 spec sheet runs from 40 Hz to 20,000 Hz, with impedance at 60 ohm and sensitivity at 102 dB SPL per mW. The drivers use neodymium magnet structures. A coiled cord with single entry stretches to 2.4 m and ends in a 3.5 mm plug, and a 3.5 mm to 6.3 mm adapter is packed with it. Two controls are built in - a volume control mounted on the earcup and a switch that toggles between stereo and mono.

Engineering and use context

Noise reduction here is achieved without batteries or electronics. Closed Pneumalite ear cushions and an extra-secure headband press the cups firmly around the ear, and Koss says this seal is intended to shut out ambient noise. The cups are high-density composite shells with thick circumaural sealing cushions, carried on an adjustable steel-reinforced sliding headband, and the wipeable shells can be cleaned between users in shared settings such as classrooms. Because no power is involved, there is nothing to charge in the field and no electronic noise floor added by a cancellation circuit. The stereo and mono switch addresses a real problem with scanners, detectors and many radios, letting a single-channel feed be heard in both ears. The earcup volume control lets the user trim level without reaching for the source, useful when a scanner sits in a car or a detector control box is strapped to the arm. The long coiled cord reaches across a vehicle cab or down to a hip-mounted unit while staying compact when not stretched.

Pairing

Given its high sensitivity, the QZ99 reaches loud levels from the small headphone outputs of scanners, detectors, handheld radios and phones. The supplied adapter connects it to home receivers, instruments and mixers, and the passive seal keeps working in noisy spaces where no mains or battery power is at hand.

Alternatives

The Koss Pro4S Studio is a closed full-size wired headphone from the same maker with aluminium earcups and a detachable coiled cord.