noun
open-back headphones
Headphones with open ear cups that allow sound to pass through, providing a more natural soundstage but less noise isolation. Often contrasted with 密閉型ヘッドホン (closed-back headphones).
See also: 密閉型ヘッドホン
開放型ヘッドホンは音漏れしやすいが、音場が広く感じられる。
Open-back headphones tend to leak sound, but they give a wider soundstage.
スタジオでは密閉型、自宅では開放型ヘッドホンを使い分けている。
I use closed-back headphones in the studio and open-back ones at home.
Compound of 開放 (かいほう, 'open') + 型 (がた, 'type') + ヘッドホン ('headphones'). A straightforward technical term.