These are the rarest Sennheiser earphones (headphones? neckphones?) that I know of. I've only ever seen two pair, and I bought both of them.

At the same time Sennheiser invented the open-back headphone concept (HD 414, which changed the whole experience of headphone listening, not to mention what it would do for the soon-to-be-invented Walkman), they also casually invented the stereo IEM and tossed it out onto the market...not QUITE getting the form factor nailed, and even their own ad copy mentions the word "stethoscope." But they seemed to love and believe in this product, as evidenced by the fact that the HD 44 remained in their catalog for years.

And yet, unlike the HD 414, the 44 just never did catch on, and even if you're 75 years old you probably never once saw anyone walking around wearing them.

But of course that's what makes the idea of walking around listening to them now so irresistible! It's not always easy to be the first, or unique, or contrarian, or eccentric. These headphones are a statement for sure.

There are adjustable ports on the back of each driver that allow you to make the IEMs either open-backed, semi-closed, or fully closed. So, Senn threw in continuously-adjustable bass tuning, at a time nobody had even included such a thing on a full-sized headphone.

The foam tips were perished on this set when I received them, and there's no official replacement available of course, nor is anybody trying to make a living by supplying replacement tips to this utterly nonexistent market.

So we have to invent solutions. The yellow Shure IEM tips I used here are do have the same form factor as the original dark gray tips. At least these tips make it possible to listen. But I think a better seal would give better bass, and maybe something like the largest Dekoni tips would do better here. (Probably remove the inner plastic tube of the Dekoni, and then stretch it over the 44's tip.)

The potential is very clear to make these sound great--I've listened on a Bottlehead, and the tiny drivers are beautiful, balanced, open, extended and airy. Reminds me of the 414 sound but actually smoother.

It's just now occurred to me that what these earpieces most resemble is the in-ear Stax models (SR 001. 002, 003). Stax makes a little kit of tips for those, and that might be the real key to getting these to sound their best.

Of course you may be more of a collector, in which case what you really want is to keep these absolutely stock!

Interested? Want to ask questions, or just discuss? Feel free. It's a great hobby, and sometimes you come across something that gives pure baffling wonderment. Stax Lambdas are like that...as are HD 600s on an OTL tube amp...and, I think in a different way these weird orange birds of paradise are in that same uncanny realm.

Free shipping and insurance, because you're brave and love an interesting challenge! Or you just have a thing for stethoscopic music.