I've just resurected my HD414's and bought some new foam pads. Just need someting that can drive 'em properly, phone or tablet just hasn't the omph required for Hi-Z headphones.
They do have nice round gold plated asymetrical bi-pin connectors. More recent Sennheiser head phones have flat pin tinned(?) connectors that are none too reliable.
I still have the HD 414s I was issued with at the BBC in the '70s. They didn't ask for them back when I left. ;-)
Useful thing with them being high impedance is they can be used on a normal power amp output in place of speakers. With care, obviously.
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