密閉 みっぺい がたヘッドホンではありませんでした
mippeigata heddohondewārimasendeshita

Noun
Desu Copula

The polite, past negative form of 密閉型ヘッドホン

1. Were not closed-back headphones.; Was not a closed-back headphone.

Past/Perfective
Negative
Polite
Formal Register