How Do Headphones Work? Forty-Nine Cards Say One Word

Forty-nine of the fifty-three headphone cards here that name a driver type say the same word. Dynamic. One says Planar, three say Bone Conduction, and fourteen don't fill the field in at all. So the answer to how headphones work is one answer for almost everything on sale. But the interesting part is what the card stops saying next.

Dynamic means a coil, a magnet and a diaphragm

A dynamic driver is a coil of wire glued to a thin diaphragm, sitting in the gap of a permanent magnet. Current through the coil makes a force, the force moves the diaphragm, and the diaphragm moves air. A subwoofer works the same way at a different scale, with a cone, a surround and a basket around the same coil and magnet.

That's the whole mechanism, and being that simple is why the word appears on 49 of the 53 cards that answer. The microphone version of the same question splits three ways, though. A microphone's element type divides its population into dynamic, condenser and electret, and a second field confirms which by asking whether power is needed. Headphones need no such field, because they're driven rather than listening, and there's nothing for a second field to confirm.

The one planar card, and what its maker says about the other kind

1 card of the 67 collected here names a planar magnetic driver, and it's the Audeze LCD-X. Instead of a coil at the centre, the conductor is printed across the whole diaphragm, and that diaphragm sits between magnet arrays. Nothing else about the job changes, and something flat still has to move air.

The useful part is that Audeze explains the ordinary driver better than the makers of ordinary drivers do, because it needs the contrast. Its page puts the mechanism plainly. Current through the voice coil exerts force "at the center of the diaphragm", but because that force starts at the centre and travels outward, not all of the diaphragm starts moving at once. Audeze calls the result breakup modes, mechanical filtering, transmission delay and local resonances, and says its own driver drives the whole diaphragm at once instead.

That description of the dynamic driver is standard physics and checkable. But the comparison that follows it is Audeze's own sales argument, in Audeze's own words. Its drivers "vastly outperform any other headphones out there" is a claim by the company selling them, not a measurement anyone here repeated, and it's worth keeping the two apart while reading the rest of that page.

Three cards leave the ear canal out of the path

3 cards name bone conduction, all of them Shokz. The transducer vibrates the bone in front of the ear rather than the air in the canal, so the eardrum is bypassed and the ear stays open. The path runs skin, temporal bone, cochlea, and the cards drop the driver size row entirely because there's no diaphragm diameter to quote.

8.4 mm to 106, and only 38 cards say which

Size is where the sameness stops. Of the sixty-seven cards, 38 state a driver diameter, and they run from 8.4 mm to 106, with a median of 40. At the small end sit a pair of Sony earbuds and at the large end the Audeze, with a Sennheiser HD 800 S at 56 and a gaming Audeze at 90. A bigger diaphragm moves more air for the same excursion, which is why the biggest numbers cluster on open-back and planar designs rather than on anything meant to fit inside an ear. That's a constraint of the ear rather than of the driver. But twenty-nine cards don't publish the number at all, so a good part of the row can't be lined up on it either way.

Fourteen cards don't name the type, and one of them is loud about it

Among the fourteene that leave the field empty are a Beyerdynamic DT 990 PRO, a Sony WH-1000XM3, a Bowers & Wilkins Px8 S2 and an Astro A50. None of them is an obscure product, and none is a cheap one.

The sharpest case is the Audeze Maxwell 2. Its listing announces "90mm Planar Magnetic Drivers" in the key features and repeats it in the description, and the specification table below carries a driver size of 3.5" / 90 mm and no driver type row whatsoever. So the shop knows what's in it and writes it in prose, but the field a comparison actually reads stays blank. Twenty-five over-ear models name a driver size, the median among them is 40 mm, and exactly three beat a 53 mm gaming headset: the 106 mm planar, the 90 mm one and a 56 mm open-back flagship.

The numbers around the driver decide more than the driver does

Two figures govern how loud a given source will drive a given pair, and the cards publish them unevenly. 42 of the sixty-one give an impedance, from 16 ohms to 470, median 47.5. Only 25 give a sensitivity, and those run from 95 to 119 with a median of 104. Audeze publishes a whole article on how the two interact with amplifier power, and opens it by calling the subject one of the more complex things headphone buyers deal with, and something even hardcore enthusiasts get confused about. When the maker of the most expensive pair here says that, the two thirds of cards that skip sensitivity are not a small omission. The mechanism is settled; the matching isn't, and the table is where that shows.

Questions people ask

What actually moves inside a pair of headphones?

A diaphragm. On 49 of the cards here a coil glued to that diaphragm sits in a magnet gap and pushes it; on one, a conductor printed across the whole diaphragm does; on three, the whole unit vibrates bone instead of air.

Are all headphones the same inside?

By driver type, nearly. Fifty-three cards answer the question and forty-nine give the same answer. But what differs is diameter, impedance and sensitivity, and only 38, 42 and 25 cards of the sixty-seven publish those three.

What's the difference between planar magnetic and dynamic?

Where the force is applied. A dynamic driver pushes from the centre of the diaphragm outward; a planar one applies force across the surface. One card here is planar and one gaming headset is planar without saying so in its table.

Does driver size mean better sound?

It means more air moved per millimetre of travel, though that's a different claim. The row runs from 8.4 mm to 106, and the largest belong to open-back and planar designs that were never going to fit in an ear canal.

Why do some headphones need an amplifier?

Impedance and sensitivity together, not the driver. The row spans 16 to 470 ohms, but the sensitivity that would say how loud each gets per milliwatt is missing from forty-two cards out of sixty-seven, and where it is stated it isn't always per milliwatt.

Sources

1. Audeze's page on planar magnetic technology: the description of the ordinary dynamic driver, in which current through the voice coil exerts force at the center of the diaphragm — most often paper, plastic or metal — and the resulting breakup modes, mechanical filtering, transmission delay and local resonances that follow from the force starting at the centre; plus the company's own case for driving the whole diaphragm uniformly instead.
2. Audeze's product page for the LCD-X: "Extra-large 106mm planar drivers", Ultra-Thin Uniforce diaphragms, Fazor waveguides and neodymium magnets, with a specification table giving the transducer as planar magnetic and the diaphragm as 106 mm.
3. Audeze on sensitivity, impedance and amplifier power: the worked example of a 70-ohm pair at 101 dB per milliwatt, and the opening admission that this is one of the more complex subjects headphone owners deal with and something even hardcore enthusiasts get confused about.
4. B&H Photo Video's listing for the Audeze LCD-X: the only card in this collection whose driver type field reads Planar, and the largest diaphragm in the row at 106 mm.
5. B&H Photo Video's listing for the Audeze Maxwell 2: "90mm Planar Magnetic Drivers" in the key features and again in the description, a driver size row reading 3.5" / 90 mm, and no driver type row at all.
6. Class counts, medians and field coverage come from listings of 200 audio products collected the same way. How those are read and compared.

All five pages were read on 27 August 2026.

What we did not do

No headphones were opened for this page. The mechanism above is described from a manufacturer's own published explanation, and the counts are of what the listings say; where a maker argues for its own technology, that's marked as its argument rather than repeated as a finding.