Bests & Worsts Reviews from Amazon

If you're reading this, you're deep enough into the audio hobby to have realized an important psychological truth about yourself: you can't leave well enough alone. Neither can I. That's why, even after falling head over heels in love with the sound of the HD650, I ordered the HD600. I just had to know. The verdict? It's almost too close to call, but for my preferences the 650 is the better headphone. The two have been compared to death online, but if you have the capacity to think for yourself, audio review sites and forums are usually an unsavory if fascinating combination of shilling, self-justification, and "follow the leader" parroting of received opinions. Many self-proclaimed "audiophiles" have strong opinions about equipment they've never actually heard, which I can't accept. Given that, I decided the only way to compare the two headphones honestly was to listen to both myself for hours, going back and forth on a wide variety of recordings. The difference between a good recording and a bad recording dwarfs the difference between lossy and lossless, and the HD600 (more so than the HD650) may end up changing your taste in music because it makes good recordings sound SO GOOD and bad recordings sound SO BAD. In other words, it reveals the "truth" of the recording, and sometimes the truth hurts—it's really hard to enjoy The Killers now. The fact is that the 600 and 650 are ultimately more alike than different, and the popular insistence that they sound completely different has more to do with what Freud called "the narcissism of small differences" than the headphones themselves. If you Google some variation on "HD650 vs HD600," you'll hear over and over that the 650 is "bassier" or "darker." Not really. There's actually very little difference across this parameter. Piano music presents an exception, but this is rarely what people think of as a bassy genre. There are two significant differences. The first is soundstage. The HD650's soundstage is wider, but that doesn't mean it can make a cramped recording sound airy. The HD600's soundstage is more intimate; there's less space between left and right channels, but it's not a huge difference, and I could see people preferring (or at least not minding) the HD600's tighter spacing. The most striking difference between the two headphones is in what I'd call "smoothness." The best analogy I can think of comes from digital photography. As an image sensor increases its sensitivity, it also increases its noise because you can't amplify a signal without also amplifying noise. There are two rival philosophies for dealing with noise: leave it as "grain" or smooth it out. Grain has its devotees, and the advantage of grain is that it preserves fine detail. The disadvantage is that past a certain point it becomes a distraction. The advantage of smoothness, meanwhile, is that it looks superficially nicer. The disadvantage is that when you look closely you won't see all the fine details. Like all things, it's a continuum of compromise. The 600 is the headphone to get if you value detail at the cost of an occasionally unpleasant grainy and even metallic quality to the sound. The 650 is the one to get if you care more about music than sound and don't care if your headphones sand down the sharp edges of your music a bit. Going back and forth between the two, it quickly becomes clear that the 650 is the stronger all-around performer: it sounds nicer on more recordings and across more genres. The 600, meanwhile, is the champion of a particular niche: good recordings with lots of micro detail. Want to be able to count how many times the skin of a drum reverberates after it's struck? Want to hear such fine vocal gradations you'll know how a singer felt during recording? The 600 is for you. Make no mistake: at its best, the 600 produces the most astonishingly detailed sound I've ever heard. Unfortunately, at its worst it sounds grainy, jumbled, and not particularly musical. I'm sorry to report that piano music sounds particularly off on the 600: low frequencies disappear and take the fullness of the keys with them. Vocals can sound oddly recessed, even far away. In general, the 600 seems to fare better with female vocals than male ones, and with strings over pianos. It's absolutely glorious for acoustic guitar, but then, so is the 650. The 650's great advantage lies in its ability to bring out vocals like a spotlight. They stand out so clearly and powerfully from the instrumentation that you'll feel like you're hearing your favorite songs for the first time. The effect is really quite incredible: it's like there's a special sonic space reserved for vocals and unpolluted by other sounds. Based on Sennheiser's own specs, the 650 has lower distortion than the 600 and it's clearly a more refined driver unit. Whatever the technical reason, the 650's background is pitch black: sounds rise from and fall back into a sea of silence. Be forewarned: a well-recorded vocal track through the 650 may bring tears to your eyes, and that's why I kept the 650 and returned the 600. Finally, let's talk about measurements. While there's a valid SUBJECTIVE argument for preferring the sound of the 600, the 650 has an objectively better driver that improves on its predecessor in every way: higher sensitivity, lower distortion, and better power handling. Here are the figures straight from Sennheiser's manuals, which you can find for yourself on the product pages for both headphones at bhphotovideo[dot]com. The terminology used isn't consistent from one manual to the other, but the parameters in question are the same. I've noted these variations where applicable. Frequency response (-10db): 12 – 38,000 Hz (HD600), 10 – 39,500 Hz (HD650) Impedance: 300 ohms (same for both) Sensitivity/"Loudness" (Sennheiser also calls this "Sound pressure level at 1 kHz"): 97 dB (HD600), 103 dB (HD650) Load rating (Sennheiser also calls this "Long-term max. input power"): 0.2W aka 200mW (HD600), 500mW (HD650) THD (Total Harmonic Distortion): ≤0.1% (HD600), ≤0.05% (HD650) In short, the HD650 will get louder than the 600 because it has higher sensitivity at the same resistance. The fact that it can handle almost twice as much INPUT power is a positive, not a negative; if you turned a decent amp ALL THE WAY UP with the HD600 connected, you could damage or even destroy the drivers. The 650 has enough headroom for more than twice as much input power, but there's little point in driving your headphones loud enough for permanent hearing loss. At the end of the day, headphone preference, like any preference, is primarily subjective, and I can't seriously imagine anyone being unhappy with the HD600.