Kuòyīn guǎn / Kuòyīnguǎn (-)
original: 扩音管
Literal translation: 扩音: "amplification"; 管: "tube / pipe".
According to the specifications of the internet source (a factory), made of copper (铜 (tóng)).
汉英词典 (Hàn Yīng cídiǎn) / A Chinese-English dictionary. 北京 [Běijīng], 1985, p.401, 826 & 250 [tóng: p.689].