The AKG K240 Sextett isn't just a pair of headphones. It's a mid-1970s broadcast monitoring statement — a closed-back, semi-open design that used six passive radiator discs to create a soundstage you'd normally need a pair of bookshelf speakers to get. AKG built these from 1975 to the early 1980s, and the Sextett (the original MP model with the six "radiators") remains the one to hunt.
Why six discs? Because AKG engineers decided that a single large diaphragm wasn't enough. They wanted the transient speed of a smaller driver but the air-moving capability of a larger one. So they gave the Sextett a 30mm driver in the middle and six passive membranes around it — each one tuned to resonate at specific frequencies, effectively turning the headphone into a miniature acoustic chamber. It's ridiculous. It's brilliant. And it works.
The sound is what separates the Sextett from every other vintage headphone. This thing does not sound like it's on your ears. It sounds like you're sitting in a small, well-treated control room listening to nearfields. The stereo imaging is unnervingly wide, with depth that makes closed-back competitors from the era — the DT 48, the HD 414 — sound flat and boxy. The bass is present but not thumping; it's more like a punchy, articulate low-end that never bleeds into the mids. The treble is smooth, rolled off just enough to avoid fatigue, but with enough air to keep cymbals and strings from sounding muffled.
What makes the Sextett special is its story. It was designed for broadcast use — think radio DJs and studio talkback — not for audiophile listening. But collectors caught on in the 2010s, and prices climbed from $50 to $300+ for a clean pair. The cult status is deserved. There's nothing else that sounds quite like it: a headphone that makes you forget you're wearing headphones.
One honest caveat: the Sextett is fragile. The passive discs are glued in and can pop loose. The foam behind the driver disintegrates. The headband padding turns to dust. And replacement parts are scarce. If you buy one, expect to open it up and glue something back together. That's the price of admission.
You don't buy the Sextett for convenience. You buy it because you want to hear Aja float around your skull like it's being played through a pair of Quad electrostatics in a living room you can't afford. It's a headphone that demands patience and gives back sound.