I just got a good listen on these headphones at a friends and thought I'd share my quick thoughts just in case anyone is interested in a vintage pair of ortho headphones. I did this listening while going back and forth between the YH-1 and my HE-500s. I've heard of these going for $60, but I only found a couple in the $100-$150 range. As far as I could tell there was nothing wrong with the pair I was listening to, but becuase of the age I wouldn't be surprised if not all YH-1s sounded the exact same.
Source was iPod5.5g LOD to Fiio E11
Build + Comfort
Dang these things are light. They're lighter than many of the good headphones out there, but still have the orthodynamic technology. They pull this off by having almost a non-existent (weight wise) headband. The build quality doesn't feel super-sturdy, but they have survived over 30 years, so that's a good sign. They are on-ear, but there is so little clamp that I didn't find them at all uncomfortable. Because of the small amount of clamp, I wouldn't want to use them while moving around much as they would probably fall off my small head.
My first thought was, "these things sound great!" They had a nice smooth presentation with beautiful mids and plenty of bass. The quick is that this has a "\" shaped response, so above flat bass, and reduced highs. These cans have a good sound, but certainly are not flat.
As I listened on, I noticed a lack of treble. The treble is there, and I could still hear every instrument without issue, but the micro detail wasn't present. Since the treble is recessed a bit, certain instruments that have their detail or texture in the highs (snare drum, trumpets, etc.) sounded a bit off. This issue isn't a deal breaker at the price point, but if you like bright or sparkly or detailed headphones than these are not for you.
The mids are just wonderful and sort of lull you to sleep becuase they are smooth and keep the focus of the music in the place we naturally want to focus. While comparing these to the HE-500, I noticed that the texture of the instruments and voices were lacking (I think due to the recessed highs). I think this acts to make the music more relaxing and soothing. In short, good mids.
The YH-1 has a surprising amount of bass. If you're a bass head this is a can to consider. I found the sound similar to a "bass boost" feature on some amps. I actually had to double check that the bass boost wasn't activated on my fiio E11. And, just like the EQ effect, this sounds great on some music that is mastered without much bass, but is overkill on already bass heavy music.
YH-1 vs. HE-500
These are obviously in different pricing categories, with the HE-500s being 4-7 times more expensive, but the comparison will at least tie the YH-1 to a more well known pair of headphones. So, the YH-1 certainly doesn't match up well. The 500 has great bass, great mids, and great treble, while the YH-1 is about the bass and mids. The texture and timbre is much more lifelike on the 500 as well. The YH-1 does have more bass than the HE-500 and "smoother" mids, but the lack of detail is the cost.
I wouldn't consider these if you're looking for something balanced or as your only headphones, unless you are a serious bass head. However, if you want to get an extra pair of headphones to compliment some balanced or bright cans then I would seriously consider these, especially if you are interested in vintage or orthodynamic headphones. After writing this all down it seems like these aren't very good cans, but they did have a good sound. For me personally, the low treble and extra bass just doesn't work well (I prefer too much treble to too much bass).
Well, hopefully this helps someone.