Headphones are simple machines, which is good news for a used buyer. Most faults come down to a handful of parts, the pads, the headband, the cable and the drivers, and most of them show up in the listing photos or in one question to the seller. Here's what to check, roughly in the order things go wrong.
Both sides, and dropouts
The single most useful question is whether both sides play at the same volume with no crackle. Ask the seller to play some music and gently move the cable where it enters each cup and where it meets the plug. A side that cuts out or crackles as the cable moves points to the cable or a connector, not the driver, and that's usually fixable.
Where it happens tells you a lot. On Sennheiser's 1980s and 1990s open headphones, such as the HD 540 Reference and HD 560 Ovation, dropouts usually come from the two-pin connectors at the cups, whose metal contact springs lose their tension. Bending them back is the fix. On a Grado SR60 or its siblings, the wired-in cable tends to break just above the plug or at the Y-split. One owner of a 1970s Koss Pro/4AA traced its failure to a short in the cord.
A side that's quiet all the time is more serious, since it can be a failing driver. On a vintage Stax that Stax no longer repairs, a weak side is a reason to walk away. The one exception is a Normal-bias Stax, where one side can play louder for a while after switch-on until both diaphragms charge. That settles down by itself.
Pads and headbands
Pads age in different ways depending on what they're made of. Foam crumbles, as the yellow discs on an old HD 414 usually have. Pleather and leatherette crack and flake, as on the HD 540 and the HD 520. Velour flattens as the foam inside softens. Look at the pads from the side in the photos, and ask for a close-up if they're hidden.
Worn pads only matter when you can't replace them, so check that before you decide. Plenty of genuine parts are still sold.
- Sennheiser still sells pads for the HD 414 and HD 424, and the HD 565 takes current HD 600-family pads.
- Beyerdynamic sells pads for the DT 100 and its EDT 990 V velour pads for the DT 880 and DT 990 range, along with headband pads.
- Koss sells cushions for the Pro4AA, the Porta Pro and the ESP/950.
- Grado sells all its cushions and says they fit every Prestige model.
Others have no factory parts at all. Beyerdynamic lists nothing for the DT 48 or DT 220, and Stax Japan has stopped supplying pads, cables and drivers for its classic models. On those, the pads in the photos are the pads you get, so judge them closely.
Headbands fail too. AKG's K 240 family hangs from elastic straps that go slack with age, and one long-term Grado SR80 owner reports the plastic part that holds the headband breaking. Check that the band is straight, that the padding is whole and that both cups hold their position.
The cable and the plug
Find out whether the cable is detachable or wired in, because it changes what a damaged one costs you. Most of Sennheiser's classics, from the HD 414 to the HD 565, use a detachable cable with its two-pin plug at the cup, the Beyerdynamic DT 100 has a single detachable cable with a multi-pin plug, and the AKG K 1000 uses a 4-pin XLR. The Grado SR series, the Koss models here, the DT 880 and DT 990 and every vintage Stax have cables wired into the cups, so damage means opening a cup or a specialist repair.
Then look at the plug itself. Many German headphones of the 1960s to 1980s came with a 5-pin DIN plug, loudspeaker plugs or even bare wires, and you'll need an adapter or a new plug. Some Grados came with a snap-on 6.3 mm adapter that's easy to lose. If a cable is detachable, make sure it's actually in the listing.
What it needs to drive it
Old headphones were built for hi-fi gear, not phones. A 600-ohm studio classic will sound thin and quiet from a phone, and that's not a fault. Each model page here says what it takes to drive the pair, and our guide to impedance and your amp explains why.
Electrostatics come as a system
An electrostatic headphone is useless without the energizer that powers it. The Koss ESP/950 works only with its E/90 energizer, and its power supply or battery box. A Stax needs an energizer or adapter box with the right bias socket, Normal with six pins or Pro with five. Check the plug in the photos and the energizer you own, or buy the two together. Our Stax bias guide lists which units take which plug.
Fakes and lookalikes
Counterfeit headphones are real, but they mostly copy current bestsellers rather than vintage models. One headphone retailer's buyer's guide says fakes tend to target very popular products, such as Sennheiser's IE in-ear line. We found no documented fakes of the vintage models on this site. What we did find is worth knowing if you shop for their modern cousins.
- Sennheiser HD 600 and HD 650. Sennheiser says the serial numbers for these are on the box only, not on the headphones, so a used pair without its box has no serial to check. Sennheiser lists the authorized sellers it stands behind, including some eBay storefronts, and tells marketplace buyers to check the Sold by name. Its warranty excludes counterfeit and grey-market products and won't accept an eBay or PayPal confirmation as proof of purchase.
- Sony MDR-7506. Sony says genuine headphones are sold sealed in good-quality packaging marked with its logo and anti-counterfeiting features such as holograms, but warns that some fakes carry fake holograms too. Owners report genuine 7506s made in Japan, China and Thailand, so the country on the label proves nothing by itself. The real thing is a 63-ohm headphone with a coiled cord and a combined 3.5 mm and 6.3 mm plug.
- Audio-Technica. Audio-Technica warns that fakes of its headphones are sold on marketplaces, auction sites and resale apps, some with its logo and some copying only the design, and that they can be nearly indistinguishable from the real thing. It won't repair or authenticate them.
- Grado lookalikes. Grado built the Alessandro MS1 and MS2 for another brand. They're genuine Grado-made headphones that look like the SR series but lack the round model button on the cups.
The common thread is to buy from a seller with a track record, be wary of new-in-box stock at a price no one else is matching, and judge the listing on its own photos rather than stock pictures.
The box and the paperwork
An original box, manual and spare parts make a pair more complete, and for some models they matter more than usual. A Stax with its matching energizer, a K 1000 with both of its cables or an ESP/950 with its E/90 and battery box is a far easier buy than the headphone alone. For a modern Sennheiser HD 600 or HD 650, the box is also where the serial lives.
Finally, ask how it will be shipped. A headphone packed loose in a padded envelope can arrive with a cracked cup or a bent headband. For model-by-model checks, start from the browse page.
