Staring at a spec sheet and wondering what the ohms mean? Headphone impedance explained: it is electrical resistance, and paired with sensitivity it tells you how easily headphones get loud from your device.
If you are still choosing a style, start with our overview of types of headphones.
| Item | Value |
|---|---|
| Impedance unit | Ohms |
| Sensitivity test power | 1mW |
| Example impedance (Audeze LCD-2) | 70 Ohms |
| Example sensitivity (Audeze LCD-2) | 101dB at 1mW |
| Impedance flagged as likely underpowered by one retailer guide | Above 100 ohms |
| Sensitivity flagged as likely underpowered by the same guide | Below 96 dB/mW |
The figures come from Audeze’s explainer on sensitivity, impedance and amplifier power and a HiFi Sound Gear guide to hard-to-drive headphones. Manufacturers and retailers can revise specifications and advice, so check the sources before you rely on them.
What impedance actually is
Impedance is measured in Ohms. Audeze describes impedance as frequency-specific opposition to an electrical input.
Think of it as how hard the headphones push back against the signal your phone, laptop or amplifier sends. It is not a quality rating, and a higher number does not mean better sound.
With equal sensitivity in dB/mW, a higher-impedance pair needs more voltage for a given listening level. Because impedance changes with frequency, the single number on the box is a summary, but it is still useful for comparing models.
What sensitivity tells you
Sensitivity relates acoustic output to a specified electrical input under stated test conditions. In plain terms, it is how loud the headphones play for a given input.
Audeze describes measuring it by applying one milliwatt of power while playing a sine sweep. Audeze identifies one kilohertz as the usual reference frequency for headphone sensitivity.
The example Audeze gives is the LCD-2, which has an impedance of 70 Ohms and a sensitivity of 101dB at 1mW. For sensitivity expressed in dB/mW, a less sensitive pair requires greater amplifier power for equal loudness.
Headphone impedance explained through the amplifier
Neither number alone predicts loudness. Audeze explains that achievable loudness depends on headphone sensitivity and the power an amplifier can deliver into that headphone load.
A practical way to read a spec sheet:
- Low impedance, high sensitivity: usually easy to run from a phone or laptop.
- High impedance, low sensitivity: usually benefits from a dedicated headphone amplifier.
- Mixed pairs: check both numbers, since one can offset the other.
There is no official cutoff between easy and hard to drive. The HiFi Sound Gear guide treats headphones as likely underpowered if they are rated above 100 ohms impedance or have a sensitivity below 96 dB/mW, but that is one retailer’s rule of thumb, not a standard.
Signs your headphones are underpowered
The retailer suggests checking whether your device can adequately drive the headphones when playback sounds weak or distorted. That is the HiFi Sound Gear guide’s view, and it matches how the numbers work.
The same guide lists these warning signs:
- Your device cannot reach your preferred listening level.
- Bass lacks weight or definition during ordinary playback.
- Increasing the level introduces audible distortion.
The guide also warns against cranking underpowered headphones to full volume, which causes clipping and distortion. The guide considers additional amplification unnecessary when ordinary playback is satisfactory.
How to check your own pair
You do not need test gear to make a sensible first judgement. Work through these steps in order:
- Find the impedance, in ohms, on the box or the maker’s product page.
- Find the sensitivity, ideally in dB per milliwatt, and note whether it is quoted per volt instead, since the two are not directly comparable.
- Compare both numbers with the rules of thumb above, treating them as guides only.
- Play a track you know well at a moderate level and listen for thin bass or distortion.
- If the pair struggles because your device cannot supply enough power, consider a headphone amplifier or a combined DAC and headphone amplifier.
Bad source files can also sound weak or harsh. The HiFi Sound Gear guide lists confusing sound quality issues with power issues, when the real problem is a poor audio file, as a common mistake.
Common misreadings of the numbers
The first trap is treating impedance as a verdict on quality. Impedance alone does not tell you how demanding headphones are; consider sensitivity alongside it.
The second trap is judging by impedance alone. Two pairs with the same ohm rating can play at very different loudness if their sensitivity differs, which is why both numbers belong in the same comparison.
The third trap is mixing units. Sensitivity can be quoted per milliwatt or per volt, and a figure in one unit cannot be compared directly with a figure in the other without adjusting for impedance. When you compare two models, make sure both are quoted the same way.
The last trap is trusting a single number as exact. Measurement conditions differ between makers, and impedance shifts across the frequency range. Use the figures to narrow your choice, then trust your ears at a moderate level.
Wireless models and amplifiers
Wireless headphones sidestep much of this. The HiFi Sound Gear guide notes that wireless headphones do not need amps, because they have built-in amplification matched by the maker.
If you are setting one up, see how to pair bluetooth earbuds for the steps. For wired pairs that do need help, the same guide describes a desktop DAC and amp combo that connects by USB and powers headphones up to 300 ohms comfortably.
For travel, it describes a battery-powered portable amplifier that fits in a pocket. Match the gear to your headphones rather than buying the most expensive option.
Loud capability versus safe listening
A big maximum figure, such as the LCD-2’s reported maximum above 130dB, describes what the headphones can do, not how you should use them. Audeze itself voices the obvious reaction: 130dB is loud enough to destroy hearing.
Easy-to-drive, sensitive headphones can reach high levels with a small turn of the volume control, so go slowly. Your hearing is the limit, not the spec sheet. Our guide to safe headphone volume covers how to set levels sensibly.
Frequently asked questions
Is higher impedance better?
Show answer
No. Impedance describes electrical resistance, not sound quality. It mainly affects how much drive the headphones need from a source.
Do I need an amplifier?
Show answer
Only if the headphones are hard to drive and your device cannot reach a comfortable level cleanly. Compare impedance and sensitivity before buying extra gear.
What unit is sensitivity measured in?
Show answer
Decibels of sound pressure level for a set input. Audeze’s example expresses it as 101dB at 1mW.
Does impedance change with frequency?
Show answer
Yes. Audeze defines impedance as resistance at specific frequencies, so the listed figure is a simplification.
