Sennheiser HD 650 headphones are a modern classic; they've never gone out of favor with the cognoscenti. Wear a pair for 10 minutes and you'll know why: They just sound right. Part of the appeal is they sound more open, less stuck inside your skull than everyday headphones. The "tone" is just right too. Bass, midrange and treble are well sorted out. They're not cheap, though. The HD 650 lists for $499 ($319 on Amazon). But the Massdrop x Sennheiser HD 6XX version we're looking at today runs $220. If you're just now getting serious about headphones, there's no better place to start than the HD 6XX.
The HD 650 looks nearly the same. The main difference is the HD 6XX headband is deep blue and the HD 650's is dark gray. The sound producing parts are the same. They're virtual twins.
The HD 6XX is an open-back, over-the-ear design, and it's very comfortable to wear for hours at a time. It comes with a six foot long, very flexible, user-replaceable cable terminated with a 3.5mm plug, and there's a 6.5mm adapter plug. Head clamping pressure against my ears was moderate, and the velour covered ear pads are just the right softness.
The HD 6XX's impedance is rated at a very high 300 ohms, but that didn't pose any problem in my listening tests. It weighs 9.2 ounces, pretty light for full-size headphones. Drop (formerly Massdrop) sells the HD 6XX with a two-year warranty, double the length of coverage of most headphones.
I used a $100digital converter/headphone amp running off my Mac Mini computer for all my listening tests. One thing is obvious from the get-go, the HD 6XX sound isn't hyped or pandering to mass market tastes. Nothing jumps out or feels amiss. The bass-midrange-treble balance is so smooth it might seem a little boring at first. But settle in with the HD 6XX and you'll find yourself hearing more and more subtle detail in your music, but without the fatigue of, say, a pair of Beats headphones.
Bass was plentiful on Massive Attack's Five Man Army all right, but not overdone. The HD 6XX's deft control over the low notes was refreshing. Vocals were likewise present and articulate. The treble was blissfully free of harshness, and the HD 6XX sounds right with the volume turned way down low or way up.
The HD 6XX is an open-back headphone, but it sounds more open and less inside my head than most open headphones, and you can easily hear sound from all around you. The downside to all open headphones is they don't isolate the wearer from external noise, and people nearby can hear sound "leaking" from the HD 6XX. So it's mostly a listen by yourself at home headphone.
I loved the sound, but it's not the sort of headphone that'll satisfy buyers craving maximum detail and clarity. If that's more to your taste, consider a Hifiman HE400S headphone (currently $229 on Amazon). It's more transparent and dynamically alive than the HD 6XX. The Hifiman is a terrific headphone, but it's not as comfortable or open sounding as the HD 6XX. The HE400S might not be a wise choice for buyers who listen to a lot of highly compressed or bright recordings. The HD 6XX would tame the harshness to some degree.
If you find most headphones too bright, the Massdrop x Sennheiser HD 6XX might be just what you're looking for. It's such an easy headphone to love because it's so darn comfortable and brings out the best in most recordings.