Pros: Great midrange, good transient response
Cons: Lack of extension, small soundstage, a bit muddy
The review is written of a modified Yamaha YH-1 which is very similar to the HP-1 but they might not sound completely the same.
Despite the supra-aural phones, the headphones are very comfortable thanks to their light weight.
The main attraction of these headphones is the midrange which is very involving and "human".
Unfortunately they are not up to today's technical standards of clearness, soundstage (although the separation is quite good) or extension but nevertheless they are pleasant to listen to. Feeding them a healthy amount of power is recommended as they will sound faster and more powerful, while they lack low bass the rest is quite nice.
Sometimes they pop up on the market for under 50$ and at that price they are great value while the plastic pieces of headpad are prone to break they are not too hard to replace and the rest seems very durable, they stand the ravage of time really well, they could be a nice addition for a vintage hi-fi system for instance.