--- title: "Headphone Impedance Explained: Ohms, Amps, and Volume" description: "What headphone impedance actually does, why 32 ohm and 300 ohm headphones need different amps, and how to tell whether yours will drive properly." url: "https://theaudiostuff.com/glossary/impedance/" type: "website" author: "Jakub Charkiewicz" --- > Markdown rendering of https://theaudiostuff.com/glossary/impedance/ > Canonical URL to cite: https://theaudiostuff.com/glossary/impedance/ > Generated from the published page. Text and links only; see the HTML for layout. Breadcrumb: [Home](https://theaudiostuff.com/) > [Glossary](https://theaudiostuff.com/glossary/) > Impedance # Headphone Impedance: What It Means and When It Matters Impedance is how much a headphone resists the current an amplifier pushes through it, measured in ohms. On its own it tells you almost nothing about how loud a headphone will play. It only matters once you pair it with sensitivity, and once you know whether your source can deliver enough voltage at that impedance. ## Work it out for your gear [Headphone Power Calculator](https://theaudiostuff.com/tools/headphone-power-calculator/) How much amplifier power your headphones need to hit a target listening level. Sensitivity (dB/mW or dB/V), impedance, headroom: required mW, RMS volts, and peak voltage swing. ## What impedance actually is Every headphone is a coil of wire sitting in a magnetic field. Push an alternating current through that coil and it moves, which moves the [diaphragm](https://theaudiostuff.com/glossary/#diaphragm), which moves [air](https://theaudiostuff.com/glossary/#air). [Impedance](https://theaudiostuff.com/glossary/#impedance) is the opposition that coil presents to the current, measured in ohms. It is not a fixed number. The value on the spec sheet is nominal, usually quoted at 1 kHz, and the real curve moves with frequency. [Dynamic drivers](https://theaudiostuff.com/glossary/dynamic-driver/) show a pronounced peak at the driver's resonance, often somewhere between 40 and 100 Hz, where impedance can climb to several times its nominal value. [Planar magnetic](https://theaudiostuff.com/glossary/planar-magnetic/) headphones are the exception worth knowing: their impedance is close to flat across the band, because the conductor is a trace on a diaphragm rather than a coil with its own mechanical resonance. ## Why the number alone tells you nothing This is where most impedance advice goes wrong. A high number does not mean a headphone is hard to drive, and a low number does not mean it is easy. What determines how loud a headphone plays is **[sensitivity](https://theaudiostuff.com/glossary/sensitivity/), not impedance**. Sensitivity says how much sound pressure you get for a given input. Impedance only tells you how that input has to be delivered: a high-impedance headphone needs more voltage and less current for the same power, and a low-impedance one needs more current and less voltage. The two combine. A 300 ohm headphone with high sensitivity can be perfectly happy on a modest amplifier, and a 32 ohm planar with low sensitivity can starve on a phone. Sensitivity and impedance are only meaningful together, which is exactly why the calculation below takes both. ## The two failure modes **Not enough voltage.** High-impedance headphones need voltage swing. A source that runs out of voltage before it runs out of current will clip on peaks while the average level still sounds quiet, and the result is a thin, compressed sound that gets worse the louder you push it. This is the classic 250 to 600 ohm problem: the headphone is not distorting, the amplifier is. **[Output impedance](https://theaudiostuff.com/glossary/#output-impedance) interaction.** An amplifier has its own output impedance, and it forms a voltage divider with the headphone. When the headphone's impedance curve is not flat, that divider changes the [frequency response](https://theaudiostuff.com/glossary/frequency-response/), because more voltage reaches the headphone where its impedance is highest. With a dynamic driver's [bass](https://theaudiostuff.com/glossary/#bass) resonance peak, a high-output-impedance source produces a bass hump that the headphone does not have on its own. The conventional guidance is the **1/8 rule**: keep the source's output impedance at or below one-eighth of the headphone's. At that ratio the response deviation stays under roughly 1 dB for most dynamic headphones. A 32 ohm headphone therefore wants a source under about 4 ohms, which most competent desktop amplifiers clear comfortably and many older or portable outputs do not. Planars are largely immune to this second problem, for the same reason their curve is flat. It is one of the genuine practical advantages of the technology, and it is why a planar can sound consistent across sources that make dynamic headphones sound different from one another. ## What to do with the number Read impedance as one of two inputs, never as a verdict: 1. Find the headphone's impedance and its sensitivity. Both are on every review on this site, in the specs table. 2. Check the sensitivity unit. dB/mW and dB/V are not interchangeable, and converting between them requires the impedance. A headphone quoted in dB/V has already folded impedance into the figure. 3. Work out the voltage and power your target listening level needs, then check your source's rated output at that impedance. Amplifier specifications are quoted per load for exactly this reason, and a figure quoted into 32 ohms tells you little about behaviour into 300. 4. Check your source's output impedance against the 1/8 rule if the headphone is a dynamic driver. ## Common misreadings **"High impedance means better quality."** No. Impedance is an engineering consequence of how the driver is wound, not a quality tier. Manufacturers offer the same headphone in multiple impedance versions precisely because the choice is about matching a source, not about performance. **"Low impedance means I can use anything."** Also no. Low impedance with low sensitivity is the hardest combination to drive well, because it demands current, and current is what small sources run out of first. **"My amp is rated 2 W, so it will drive anything."** Only into the load that rating was measured at. Power into 32 ohms and power into 300 ohms are different numbers on the same amplifier, and the one printed on the box is usually the flattering one. ## Keep reading - [Best Headphone Amplifiers](https://theaudiostuff.com/guides/best-headphone-amplifiers/) - [Full audio glossary](https://theaudiostuff.com/glossary/) - [How we test and score](https://theaudiostuff.com/about/#methodology-title)