One of the first lessons you learn after diving into the world of hi-fi audio is that no pair of speakers or headphones can ever be declared as the best. Even if you're rich (or mad) enough to spend hundreds of thousands of dollars on your audio setup, there's still a chance someone will listen to it with a straight face and remain utterly unimpressed. The main reason for this is that not everyone enjoys the same character of sound. What you could potentially find ideal, someone else may consider lacking in certain aspects. For example, I generally don't like when the bass is heavily emphasized, but there are plenty of users who wouldn't give a second thought to a pair of speakers or headphones that aren't exceptionally bass-heavy. That's okay, and don't let anyone tell you otherwise.

With that in mind, it's quite impressive what Sennheiser managed to pull off at around the turn of the century: they released two products that were met with universal acclaim by users and critics alike. In 1997, they released the now legendary HD 600, followed by the equally famous HD 650, launched some six years later. Both headphones share many characteristics—both were positioned as the company's flagship products, open-back, and almost universally liked, nay, loved by their owners. With a launch price of around $500, neither were exactly cheap, but for countless users, they represented the "endgame"; that last pair of headphones they'd ever need to buy. Over time, their price dropped significantly; nowadays, you can pick up the HD 600, as excellent as ever, for no more than $300, and the HD 650 for around $400. Let's not forget the Massdrop-exclusive HD 6XX, which is basically the HD 650 with a navy blue instead of a black color scheme—more than 40,000 users bought them (and continue buying them) for a measly $200, which is a bargain of a lifetime.