If you could only have one headphone in your inventory, what would you pick? For me, it would be the Sennheiser HD 600.
Yes, there are scads of headphone models available. They all have strengths and shortfalls. Many of us get caught up in the “headphone of the month” club, where headphones are routinely bought, enjoyed, and sold, onto the next model to try out. The new model often does something “better” than the one just sold. After listening to it for awhile, you start to notice flaws, and move on to the next headphone.
The one headphone many have in their collection that does not get sold is the venerable HD 600. Introduced in 1997, 29 years later, it STILL is among the best overall models a headphone enthusiast has available. The overall balance provided by the headphone is so good, Sennheiser, with all the models that have come out since then, have had a bugger of a time providing a product that betters the HD 600 in all across the board aspects of reproduction.
What the HD 600 gets right that most headphones fall short in is the midrange. Very few headphones at any price can match the overall balance the HD 600 midrange provides. If the midrange is not right, then the overall sound is not right. It’s surprising just how many expensive headphones miss the mark on midrange performance. The HD 650 gets close, but IMHO, the HD 600 betters the HD 650 in the midrange by a small but noticeable difference.
The tradeoffs with the HD 600 is the lower bass is attenuated, but not to the point where it degrades the playback. I find a lot recordings artificially elevate the bass, which is not how a lot of live music actually sounds. The presence/treble region with the HD 600 is cited by some as harsh, but I find it to be more accurate/neutral.
In summary, whilst the HD 600 is not the best headphone money can buy (God only knows what that is) the HD 600 is the one headphone that I could live with long term if one had to choose only one headphone to own. The fact that replacement parts are readily available, and that it’s performance can upscale with better electronics is icing on the cake. Hook it up to a high quality OTL tube amp, and one is in for a real treat.