Notes on IEMs

These are my notes on what I have learned about IEMs and wired headphones in the hobby - the one graph that explains almost everything, what the technical terms actually mean, and the gear that is easy to recommend. All of it in plain terms, so it is easy to find your way into a genuinely rewarding hobby.

The Only Graph That Matters

Every earphone has one defining property: how loudly it plays low notes versus high notes. That is the whole secret. Plot it on a chart - frequency from left (deep bass) to right (shimmering highs), loudness up and down - and you get a frequency response graph. Reviewers treat it like scripture, and the reverence is earned: research on listener preference keeps finding that this curve explains most of why an earphone sounds good or bad to people [1]. Not the driver count, not the cable, not the price tag. The curve.

The graph splits naturally into five regions, and once you know what lives in each one, you can read any earphone review chart like a menu:

One thing trips everyone up the first time: that big hill around 3 kHz. It looks like a flaw. It is actually your own anatomy. Your outer ear and ear canal naturally amplify frequencies in that range by roughly 10 dB before they reach your eardrum. An IEM bypasses part of the outer ear, so a good one has to build that boost back in. A frequency response that looks like a flat line would sound dull and wrong. The hill is the earphone doing your ear's job for it.

What Should the Line Look Like, Then?

For decades the honest answer was “nobody knows, buy whatever the magazine likes.” Then a research team at Harman International, led by Sean Olive, did something refreshingly scientific: they put hundreds of listeners through controlled blind tests, let them tune bass and treble to taste, and measured what people actually preferred [1]. The result is the Harman target curve - a moderate bass lift, a clean midrange, and that natural ear-gain hill, followed by gently declining treble.

The follow-up studies are the interesting part. Roughly two-thirds of listeners preferred the Harman target as-is, while the rest split into a camp that wanted more bass and a smaller camp that wanted less [2]. In other words: the target is not a law of physics, it is a very well-tested crowd-pleaser - and your personal taste probably sits either on it or a nudge to one side. The audio community describes those nudges with a handful of named sound signatures:

In words: Harman is the tested default - a touch of extra bass, clear vocals. Neutral plays the recording straight, nothing boosted - the studio reference sound. V-shaped lifts both bass and treble and lets the vocals step back - exciting at first listen, which is why so many store demos are tuned this way. Warm adds low-end body and relaxes the treble - smooth for long sessions. Bright pushes detail and air forward at the cost of eventually tiring your ears. None of these is objectively best. They are flavors, and the graph is just the recipe written down.

Which One Is Yours?

The fastest shortcut to your signature is the music you already listen to. This is a starting point rather than a rule, but it gets you to “probably right” without buying five pairs:

The Technical Terms, Translated

Beyond the frequency response, reviews lean on a small set of recurring words. Here is the whole dictionary you actually need:

• Soundstage - how big the invisible room around your head feels. Open-back headphones excel here; IEMs are naturally more intimate.
• Imaging - whether you can point at each instrument in that room. Matters a lot for gaming footsteps.
• Detail / resolution - how many small textures survive: fingers sliding on strings, the breath before a verse.
• Timbre - whether instruments sound like themselves. A piano with off timbre sounds like a keyboard ringtone of a piano.
• Sibilance - the sharp, spitty edge on “s” and “t” sounds when treble misbehaves. Once you notice it, you cannot un-notice it.

Spec sheets also love advertising what is inside the shell. The four driver technologies are worth knowing - mostly so that driver-count marketing stops working on you:

Do You Need an Amp? (A Small One Helps)

You do not need a desk full of amplifiers to enjoy IEMs - but the answer is no longer a flat no either, because phones killed the headphone jack. Something has to sit between your USB-C port and your IEMs anyway, and that something matters more than people expect: my own IEMs stepped up noticeably when I swapped a bare adapter for a proper dongle DAC. The humble $10 Apple dongle measures genuinely well and is the floor; dongles in the $20-100 range (Moondrop Dawn Pro, FiiO KA11) add cleaner power and a lower noise floor on top. Full desktop amps only matter if you someday wander into full-size territory - high-impedance headphones and power-hungry planars.

One caveat: the chain is only as good as what you feed it. Bluetooth compresses everything it touches, and standard Spotify streams are lossy - so a wired IEM with a dongle DAC only delivers its actual output when the source is lossless. Apple Music includes lossless at no extra cost; Tidal, Qobuz, and Amazon Music have equivalents. Wired IEMs plus a lossless subscription is the cheapest genuine upgrade in this whole hobby.

My Go-To Picks

Everything below is a boring, community-consensus staple - the kind of pick that shows up in every “best under X” thread for years because it keeps being right. The signature chips reuse the colors from the chart above.

Before You Hit Buy

• Seal first, judge second. An IEM without a proper seal loses its bass entirely. If a pick sounds thin, try the next ear-tip size up before writing a bad review in your head.
• Look up the graph. Community databases like squig.link [3] overlay measured frequency responses against the Harman target for thousands of IEMs. Thirty seconds there beats thirty minutes of adjective-heavy reviews.
• Ignore driver-count marketing. A well-tuned single dynamic driver beats a badly-tuned eight-driver hybrid every time.
• Mind the volume. IEMs sit close to your eardrum. The old 60/60 rule - under 60% volume, breaks after 60 minutes - is crude but keeps your future self hearing cymbals.
• Respect diminishing returns. The jump from $25 to $100 is enormous. The jump from $100 to $1,000 is an expensive shrug. This hobby is kindest to people who stop at “happy.”

That is the whole game: learn one graph, know your flavor, buy a boring consensus pick, get the tips to seal. The gear above will outresolve most people's source files long before it becomes the bottleneck - and if you catch yourself browsing graphs at midnight for fun anyway, welcome. It is a good rabbit hole.