HD650 vs HD600 vs AKG K702: Three Classics, One Decision

There’s a trio of open-back headphones that keeps coming up in every “what should I buy” thread in the audiophile community — and for good reason. The Sennheiser HD600, HD650, and AKG K702 have been around long enough to become reference points rather than just products. They’re the headphones people compare everything else against.

All three are readily available on the used market for well under their original retail prices. All three are open-back dynamics. All three reward good amplification. And yet they sound distinctly different — different enough that picking the wrong one for your listening habits will leave you underwhelmed, while the right one might just rearrange your entire relationship with music.

This isn’t a standard review — we haven’t done a fresh out-of-box listen for this piece. It’s a comparison guide based on extended time with all three, aimed at helping you decide which of these classics belongs on your head.

Quick specs

Sound — Sennheiser HD600

The HD600 is the reference point in this comparison. It’s the headphone that gets described as “neutral” — which in practice means it doesn’t editorialize much. Bass is tight and accurate without reaching deep into sub-bass territory. The midrange is slightly forward and exceptionally natural — acoustic instruments, in particular, sound convincingly real. Treble is smooth and well-extended without being aggressive.

What makes the HD600 special isn’t any single characteristic — it’s the coherence. Everything hangs together. It’s a headphone that disappears and lets you focus on the music rather than the presentation. If the HD650 is a comfortable armchair and the K702 is a laboratory workbench, the HD600 is a perfectly adjusted studio monitor. Versatile across genres, it’s also the easiest of the three to live with long-term.

Sound — Sennheiser HD650

The HD650 wears its personality on its sleeve. The bass is warmer and more present than the HD600 — not elevated in a boomy way, but rounded and full. The midrange has a richness to it that makes vocals feel intimate and instruments feel weighty. There’s a famous “veil” that gets discussed endlessly in audiophile circles — a slight softness in the upper midrange and lower treble that takes a little edge off the presentation.

Whether that’s a flaw depends entirely on who you are. For listeners who find analytical gear exhausting, it’s a feature. For genres like jazz, blues, classical, and acoustic folk, the HD650 is simply glorious. It’s the headphone you reach for at the end of the day when you want to sink in. The trade-off is that it’s less revealing of fine detail, and less suited to genres that benefit from speed and crispness.

Sound — AKG K702

The K702 is the outlier. Where the Sennheisers are warm and forgiving, the K702 is clinical and forensic. Bass is tight and precise but noticeably lean — this is not a headphone for bassheads or hip-hop. The midrange is transparent and highly detailed, and the treble is extended and bright — occasionally to the point of fatigue on poorly mastered recordings or with a harsh source chain.

What it does exceptionally well is soundstage. The K702 has one of the widest, most spacious presentations of any dynamic headphone in this price bracket. Instrument separation is excellent. For classical orchestral music, acoustic recordings, and studio monitoring applications, it’s a genuinely impressive tool. It also has the lowest impedance of the three, making it the easiest to drive — though it still scales well with a good amp. The main caveat: it rewards well-recorded source material and punishes the rest.

Build & comfort

All three are open-back, which means no noise isolation and significant sound leakage — none of these belong on public transport or in shared offices. At home on a quiet evening, the open-back presentation is part of what makes them special.

The HD600 and HD650 share the same physical platform — identical weight, similar earpads, and a headband that fits a wide range of head shapes well. Clamping force is firm but not uncomfortable. The K702 is the lightest of the three and features a self-adjusting headband that many find more accommodating over very long sessions. Its velour earpads are plush. All three are well-built without feeling particularly luxurious — these are tools, not jewellery.

Amplification

This is the most important practical consideration. The HD600 and HD650 are both 300Ω headphones — they will not perform well from a phone or laptop headphone jack. You need a dedicated headphone amplifier, and ideally a decent DAC upstream. The good news is that they don’t require esoteric gear — a Schiit Magni or JDS Labs Atom is more than enough to make them sing.

The K702 at 62Ω is easier to drive, but it too scales meaningfully with better amplification. Don’t let the lower impedance fool you into plugging it into a phone and calling it a day — it still benefits significantly from a proper source. Budget at least an entry-level DAC/amp stack alongside whichever of these you choose.

Comparative scores

Who should buy which

Closing thoughts

The right answer here genuinely depends on you. All three are classics that have earned their reputation over decades and multiple driver revisions. None of them are wrong choices — they’re just different tools for different ears and different music.

If you’re torn between the HD600 and HD650, the easiest advice is to consider what you listen to most. Rock, pop, and varied genres? HD600. Long sessions of jazz, classical, and acoustic? HD650. If you’re coming at this from a monitoring or classical background and want that wide, detailed window into your music, the K702 is hard to beat for the price — especially used.

One final note: all three are readily available second-hand for well under their retail prices. There has never been a better time to pick up one — or all three.