Sennheiser HD 600
Open-back reference headphones — the mixing standard for flat, honest monitoring.
The HD 600 has been around since 1997. It's not flashy, not bass-heavy, not exciting. That's the entire point — and that's why it's still the reference headphone for mixing engineers nearly three decades on.
Here's what you need to know.
Specs
Sonic Character
The HD 600 is famously neutral. Not neutral in the way marketing copy uses the word — actually neutral, to the point where some people find them boring. That's the highest compliment you can pay a reference tool.
There's a slightly warm midrange that makes long mixing sessions comfortable without masking detail. The top end is natural and extended but never hyped — you won't get fatigued at hour four, and you won't be fooled into thinking a mix has more air than it actually does. The bass is accurate and controlled, not boosted. You hear what's there, nothing more.
If you're used to consumer headphones or anything with a "fun" tuning, the HD 600 will sound flat. That's the point. What you hear is what's in the mix. No flattery, no deception.
Open-Back Explained
The HD 600 is an open-back design, which means the ear cups aren't sealed. Sound leaks out, and ambient noise leaks in. This is a deliberate engineering choice, not a flaw.
Open-back headphones produce a more natural soundstage — the stereo image feels wider and more speaker-like, without the artificial bass buildup that closed-back designs create by trapping air against your ears. For mixing, this is ideal. You get a more honest representation of how your mix will translate to speakers.
The trade-off is obvious: these are not for tracking. Any sound leaking out of the headphones will bleed straight into your microphone. They're also useless on public transport, in a shared office, or anywhere that sound isolation matters. The HD 600 is a studio tool for mixing, full stop.
The 300 Ω Impedance Issue
This trips people up. The HD 600 has an impedance of 300 Ω — significantly higher than the 32 Ω you'll find on most consumer headphones. Plug them into a phone or laptop headphone jack and they'll sound quiet, thin, and lifeless.
They need a proper headphone amplifier, or at very least an audio interface with a strong headphone output. Most decent interfaces — the Scarlett 2i2 and upwards — will drive them adequately, though a dedicated headphone amp will get the best out of them. Budget around £50–100 for a basic amp if your interface's headphone out isn't up to the job.
This isn't a fault with the headphones. Higher impedance allows for better driver control and lower distortion. It just means you can't treat them like earbuds.
Check frequency response curves →Why They're the Standard
The HD 600 has been the mixing reference for studio engineers for decades, and the reason is simple: mixes made on them translate. If a mix sounds right on HD 600s, it will sound right on studio monitors, car stereos, laptop speakers, and earbuds.
That's the only thing that matters in a reference tool — honesty. The HD 600 doesn't add anything, doesn't subtract anything, and doesn't flatter anything. It shows you the truth, and you make decisions accordingly.
They're also remarkably consistent unit to unit, and every part is replaceable — pads, headband, cable, even the drivers. A pair of HD 600s can last a lifetime with basic maintenance.
HD 600 vs HD 650 vs HD 660S
Sennheiser makes this confusing, so here's the short version:
HD 600 — The flattest of the three. Neutral midrange, natural top end, controlled bass. The mixing reference. 300 Ω.
HD 650 — The warmer sibling. More bass presence, slightly smoother treble, a touch less analytical. Some engineers prefer these for long sessions. Still 300 Ω. Not as flat, but not far off.
HD 660S — Lower impedance (150 Ω), easier to drive from weaker sources. Slightly different tuning — closer to the 650 than the 600. More convenient, less pure as a reference.
If you're buying specifically for mixing and you have a decent headphone amp or interface, the HD 600 is the one to get. If you want something you can also plug into a laptop without an amp, look at the 660S.
What They're Not
Not for tracking. Open-back means bleed. Your click track and backing track will leak into the microphone. Use closed-back headphones for recording.
Not bass-heavy. If you want thumping low end for casual listening, these will disappoint you. The bass is accurate — it's there when it's in the recording, absent when it's not. That's the difference between a reference tool and a consumer product.
Not portable. They're large, open-back, high-impedance, and have a long cable. These stay at the desk.
Recommendations
The reference. Neutral, honest, built to last.
View →Warmer sibling. More bass, slightly less analytical.
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