Impedance and Sensitivity Explained: Does Your IEM Need a DAC/Amp?

You've done the research, read the reviews, and finally pulled the trigger on a pair of IEMs the audio community won't shut up about. They arrive. You plug them in. And they sound... fine. Not bad. Just quieter than expected, maybe a little flat. You're pushing 90% volume to get a comfortable listening level. Something's off and you can't name it.

Here's the thing: it's probably not the IEMs. There are two specs that determine whether your gear will actually shine from a given device, and most buyers don't look at either of them. Impedance and sensitivity. Five minutes to understand. Potentially years of better-sounding audio.

Impedance: how hard your source has to work

Impedance measures how much an audio device resists an electrical signal, measured in ohms. For IEMs, it tells you how hard your phone or DAP has to push current through the driver.

Most IEMs sit between 8 and 32 ohms. That's intentional -- they're designed for portable devices, which don't produce much power. Studio and audiophile over-ear headphones are a different story: 150 to 600 ohms, and they need a proper amplifier to reach a satisfying volume.

The mismatch problem cuts both ways. A high-impedance headphone into a phone means thin, anemic volume -- the source can't push enough current. But plug a very low-impedance IEM into a source with high output impedance (a cheap amp, or a phone with a mediocre headphone jack), and the frequency response shifts. Bass goes wrong. Midrange gets coloured. What you hear isn't what the manufacturer intended. The general rule: your source's output impedance should be no more than one-eighth of your IEM's impedance. Lower is better.

Sensitivity: how loud your IEM gets per unit of power

While impedance is about resistance, sensitivity is about efficiency -- how loud your IEM gets for a given amount of power. Usually measured in dB/mW (decibels per milliwatt) or dB/Vrms (decibels per volt).

That distinction matters more than people realise.

Most IEMs land between 100 and 120 dB/mW. Higher numbers mean louder output for the same input -- a 110 dB/mW IEM is easier to drive than one rated at 98. Straightforward enough. But when comparing specs across brands, the dB/mW vs dB/Vrms thing trips people up. Because power equals voltage squared divided by impedance, a sensitivity rating in dB/Vrms is influenced by impedance in a way dB/mW isn't. A high-impedance IEM rated at 110 dB/Vrms can actually be harder to drive than a low-impedance IEM rated at 100 dB/mW. If you're comparing specs to figure out whether you need an amp, hunt for the dB/mW figure. It's more honest.

How the two numbers talk to each other

Neither spec tells the whole story on its own. That's the thing people miss.

A low-impedance IEM should be easy to drive, and usually is. But pair it with low sensitivity -- say, a planar magnetic IEM at 8 ohms and 96 dB/mW -- and your phone may still struggle, because low-impedance sources output voltage rather than current.

Flip it: a high-sensitivity IEM (115 dB/mW at 16 ohms) gets plenty loud from your phone. But it also picks up the noise floor of your source. Faint hiss. Static. A background hum you notice in quiet passages between tracks. That's not a power problem -- a more powerful amp won't fix it. You need a quieter one.

This is why plenty of audiophile-targeted IEMs land at moderate sensitivity, around 104 to 108 dB/mW. Loud enough to drive from a phone, quiet enough to avoid hiss from noisy consumer sources.

So does your IEM actually need a DAC/amp?

Probably not. Most modern IEMs run fine from a phone. Flagship devices from Apple, Samsung, and Google have capable audio hardware built in. The era of universally terrible phone headphone output is mostly behind us.

That said, there are signs your source is holding things back.

You're maxing volume just to reach a comfortable level. Past 85 or 90% on your phone, the source is underpowering the IEMs. More power isn't just about loudness -- it's dynamic control. Bass tightens. Transients sharpen. The whole presentation opens up.

You can hear hiss. A faint hiss in quiet passages, especially with sensitive IEMs, is the source's noise floor leaking in. A DAC/amp with lower output noise (measured as SNR) cleans this up.

You're on a laptop headphone jack. Laptop audio is inconsistent in ways phone audio isn't. The headphone output shares a board with components that introduce interference. A USB DAC bypasses the whole problem.

A DAC (digital-to-analogue converter) takes the digital signal from your device and converts it to an analogue signal your IEMs can use. An amp takes that signal and amplifies it cleanly. Most portable units do both in one dongle you plug into USB-C. If your IEMs are under 32 ohms and over 105 dB/mW, your phone is almost certainly sufficient. Planars, anything above 150 ohms, or anything with sensitivity under 100 dB/mW -- that's where a dedicated source starts making sense.

Where to start if you do need one

Entry-level DAC/amps have gotten good. There are solid options under $50 that outperform most built-in phone audio without any fuss.

For portable use, a USB-C dongle DAC/amp sits between your phone and your IEMs, draws power from your device, and requires nothing else. For desktop, a small stack connects via USB and outputs via 3.5mm or 4.4mm.

Start with your phone. If something sounds off -- thin, quiet, hissy, lacking bass weight -- try the source before you try new IEMs.

The short version

Under 50 ohms and over 100 dB/mW sensitivity? Your phone's probably fine. If it sounds wrong, check the source before you spend on new gear.

Impedance and sensitivity aren't intimidating once you see what they're measuring. They're just two numbers that describe how your IEM and your source device talk to each other. Know the numbers, match the gear.

Browse the Lumontier range to find IEMs matched to your listening setup.