Pros - Very comfortable to wear (if the plastic headband has decent flex), very nicely balanced sound that's non-fatiguing
Cons - You do have to replace the earpads from time to time; open-air design does not work for all situations
I own two pair of these, both the original 600-ohm model from the mid 70s. I still use them quite frequently, they are my favorite headphone.
One pair has a tighter headband with less flex - probably my "2nd pair" that did not get used as much. This squeezes my head a bit - and I have a smallish head as heads go. So if you are buying a used pair, be sure to check this aspect for your comfort. Replacement parts are harder to come by now.
There are still a variety of cord replacements available with the right earpiece jacks, the newer shorter cords with the mini-plugs work well. I found a replacement cord for around $12 shipped that I like better than the OEM Sennheiser cords for $30.
The main concern I hear expressed about these is the impedance. With my convenient sources such as cell phones and iPods, the volume level is high enough for me for normal listening. You can't get it super loud, but that's very bad for ears anyway. With a headphone amp such as the Schiit Fulla, or a normal headphone in on a receiver, there is of course no problem at all.
After 40+ years of continuous use, the drivers are still just fine. The plastic they used, don't know what it is, but mine have not yellowed at all. I suppose if you use outdoors a lot, that might be different.
If you like open-air designs, these are worth tracking down. To me, they are "THE" headphone, because they were my first. Even that awful original box photo makes me smile, because I remember buying them.
My hearing now extends only to about 13,600cps so these have quite sufficient highs for me. I suppose some young ears might deem the top end a bit rolled off. Bass is good for me, not bloated, just right.
Pros - Very high impedance & high sensitivity, built to last, reasonable detail
Cons - Lots of midrange, no bass and only a bit of treble, pretty much like most 60s headphones, awful cable
I don't usually do hands-on reviews, but in this case I'm quite certain. I got my pair of HD414 for a bargain price, still in EX/VG condition, only a bit dirty on the inside.
What originally caught my attention was 2000 Ohm impedance. I was like...really?!? Apparently someone caught up to the idea of high voltage/low current, which was perfect for me. At 2kOhm and 102dB/mW this looks like the perfect set of cans to be driven from virtually anything, even line outs!
Unfortunately while this looks great on paper, the light-speed fast transients that could result from such high impedance are not there.
Sound is vastly oriented around mid range, with no bass and only bits of treble. Kinda reminds me of Koss Pro4AAT. Non existent soundstage and highly attenuated detail.
As for comfort, my experience could be a bit biased as the pads are quite worn off, but HD414 are by far the least comfortable cans I tried.
But there is still hope.
I'm quite certain this veiled, uninteresting, degraded sound signature is the symptom of that headphone cable. Honestly I didn't see anything that'd measure worse than this.
Almost 12Ohm resistance over 2.5m, 180pF capacitance between all three wires, straight (not twisted) pairs and no isolation. This has to be the worst cable I've ever seen and is bound to negatively impact sound.
Once new cable is built, I'll update the rating to reflect the change.
After applying 4mm of soft foam onto the worn off pads, the good sound finally started to shine through. Treble started to appear, and surprisingly (or not), very clean.
I must say that i have yet to find a better sounding pair of headphones in this price range and i have try ed many! I still find then very comfortable and in all these years they have not broken although the ear pads need replacing quite often,otherwise all the parts are original.
Over the years i have brought a number of headphones but when they break or fail i always find myself going back to my old Sinnheiser HD 414s.
Can't say more then that their just great!!!!!!!!!!!!!!!1