I just finished a strange transaction for an amplifier and tossed in was a pair of Yamaha HPE-5 headphones. In the hour or so that I've had them, there does not seem to be any info online concerning that model that I have seen. Are they a legitimate stand alone headphone or were they included with some sort of portable device? Can't try them yet, but they look and "feel" somewhat OK. Years ago I had some Koss PortPro's I quite liked and this Yamaha pair kind of remind me of those.
FWIW, just now happened to find an expired e-bay listing showing the box they came in. Says for Yamaha keyboards and the retail sticker - $64.95.
The PortaPro's I had were first generation,. I believe they were smaller than modern iterations and had that sort of "D" shaped piece that sat on your ears. The inside surface was lined with closed cell foam of some kind and it liquified over time. I used those more than any other 'phone's I owned.
One feature of the Yamaha evident from the image is the choice of using them open or closed. Have not seen that before (but then, I don't get out much) and found that intriguing.
