I bought my HD414s in 1973 and they still work great! I've replaced the foam ear pads many times, Sennheiser still sells them. I also replaced the cord with a 1/8" mini plug. Bass response is not as good as an over the ear phone, but it's great for an open ear set. The high impedance makes it...

The world’s first open headphones. First released in 1968. With more than 10 million units sold, the HD 414 remains the bestselling headphone ever.