By Rejhan Kavazbasic · 9 min read · Updated 5 November 2026
Hi-fi glossary: soundstage, imaging, sibilance and more
The words reviewers use, in plain language: what you hear, and where it shows on a frequency graph. From sub-bass and sibilance to soundstage, imaging and driver flex.
Why reviewers have their own language
Read three reviews of the same IEM and you'll come across words like sparkle, bleed and holographic. It can feel like a club with its own jargon. Yet most of these words are quite down to earth once you know what they point to: a part of the frequency range, a sense of space, or a technical property.
We've sorted them into four groups: tonal balance, space, detail and technical terms. Where a word belongs to a frequency range, we tell you where to look on the graph. How to read the graph itself is in our guide to frequency-response graphs.
Above about 8 kHz, IEM measurements vary a lot between rigs and with fit.
Approximate ranges: not every reviewer draws the lines in the same place.
Tonal balance: what's loud and what's soft
Tonal balance is how loud the low, middle and high parts of the sound are compared with each other. This is the part of a review you can check best against a measurement.
| Word | What you hear | On the graph |
|---|---|---|
| Sub-bass | Rumble and pressure you feel more than hear: the lowest synth notes, an organ pedal, an explosion in a film. | 20 to 60 Hz, far left |
| Bass or mid-bass | The punch of the kick drum and the body of a bass guitar. | About 60 to 250 Hz |
| Mid-bass bleed | The bass spills into the lower mids. Voices and guitars sound thick and a bit muffled. Reviewers also say muddy. | A broad hump that runs on from the bass to 300 to 500 Hz |
| Warmth | Full, soft and pleasant. A little extra low end, or treble that's held back a bit. | Slightly raised around 100 to 400 Hz, or a curve that slopes gently down towards the treble |
| Mids | Voices, guitar, piano: most of the music. | 250 Hz to 2 kHz |
| Presence | How close and clear voices and instruments sound. Too little sounds veiled, too much sounds shouty. | 2 to 5 kHz, around the big bump |
| Sibilance | S, T and SH sounds that hiss or sting. | A narrow peak somewhere around 5 to 9 kHz |
| Sparkle | The shine on cymbals and the crispness of an acoustic guitar string. | About 8 to 12 kHz |
| Air | A sense of openness up top: a cymbal dying away, the reverb of a hall. | Above about 10 kHz |
| Bright or dark | Bright: lots of treble energy, fresh and lively. Dark: treble held back, calm, sometimes a bit dull. | The treble sits above or below the target |
- ZSN Pro
- Leá
Measured by Super* Review (IEC 711 clone), published on squig.link. Independent measurement, not by us. Measuring rigs differ slightly above 8 kHz.
The IEM or the recording?
Some recordings are sibilant themselves. If one song stings on every pair you try, it's the song. If every song stings on one pair, it's that pair.
Signatures: the shape of the whole curve
A signature sums up the whole shape in one word. The labels on our product pages are read from the measurement: we compare the bass and treble with the target.
- V-shaped: more bass and more treble, with the mids a little set back. Energetic and exciting. Vocals can sound a bit further away.
- U-shaped: the same idea, but the dip in the middle is wider and shallower. Reviewers use the two words loosely.
- Neutral: less bass than the Harman target, so the mids and details come forward. Honest and clean, but it can sound a bit lean if you're used to more bass.
- Warm and bass-heavy: extra low end. With bass-heavy the bass clearly stands out.
- Harman: close to the Harman target. Not flat, but with a moderate bass lift and a clear presence region.
The Harman target comes from listening research at Harman International, led by Sean Olive. Listeners compared the same headphones and IEMs with different tunings, and the curve describes what they liked best on average. There's a version for IEMs (Harman IE 2019) and one for over-ear headphones (Harman OE 2018). It's still an average: the research also found groups of listeners who wanted more or less bass.
- Ink
- Leá
Measured by Melatonin (IEC 711 clone), published on squig.link · Measured by Super* Review (IEC 711 clone), published on squig.link. Independent measurement, not by us. Measuring rigs differ slightly above 8 kHz.
Space: soundstage, imaging and separation
These words are about where you hear the sound, not how loud each part is. You won't find them on a frequency graph.
| Word | What it means |
|---|---|
| Soundstage | How big the sound feels: how far it reaches to the left and right of your head, and sometimes in front of you. |
| Imaging | How precisely you can point at each instrument. With good imaging the vocals sit exactly in the centre and a guitar has a fixed spot, rather than a vague cloud. |
| Separation | Whether you can keep following one instrument in a busy passage, like the bass line under a full band. |
| Depth or layering | Whether some sounds seem to stand further back than others. |
Wide and sharp
The sound reaches well beside your head and every instrument has a fixed spot.
Narrow and vague
Everything plays close to or inside your head and the instruments blur together.
With an IEM the sound starts in your ear canal, so most of the picture forms in or just around your head. That's normal. Open-back headphones usually sound more spacious than closed-backs and IEMs, as our headphone guide explains.
The recording decides a lot. A studio mix puts every instrument somewhere between left and right, and no IEM moves it further out than the mix does. Imaging does depend on the IEM: if the left and right sides aren't equally loud, the centre shifts to one side. That's why some reviewers publish left and right separately. Our graphs show the average of both.
Separation partly comes down to tonal balance. A big mid-bass hump lays a blanket over the lower mids, and then instruments in that range blur together.
Detail, dynamics, timbre and fatigue
| Word | What it means | What drives it |
|---|---|---|
| Detail or resolution | Hearing small things: a breath, the tail of a reverb, a finger sliding over a string. | Partly the level of presence and treble. That's why bright IEMs are often called more detailed. Fit counts too: a tip that leaks lets outside noise cover quiet details. |
| Dynamics, punch, slam | How big the step between soft and loud feels, and how solidly a kick drum lands. | Mostly the recording. A lot of pop is mastered loud and compressed, which leaves little difference to hear. In the bass, the sub-bass and mid-bass level and a good seal play a part. |
| Timbre | Whether an instrument sounds like itself: a piano like wood and felt, not metal. A voice with its natural weight. | Mostly the balance between fundamentals and overtones. A lean lower midrange or a treble peak can make things sound thin or metallic. |
| Coherence | Whether an IEM with several drivers sounds like one source. | The hand-over between the drivers. Our guide to driver types explains why. |
| Fatigue | Wanting to take the IEMs out after half an hour, even though nothing is obviously wrong. | Usually too much energy between 2 and 8 kHz, or simply listening too loud. Our guide to safe listening covers volume. |
Detail or just treble?
'More detail' in a review often means 'more treble'. If you're sensitive to treble, check the graph before you believe the word.
Technical terms in one line
- Driver flex: a crinkling or clicking sound when you push in an IEM with a dynamic driver. Air pressure briefly pushes the membrane inwards. It's common with a deep, tight seal and usually harmless. Inserting more slowly or trying another tip often helps.
- Sensitivity: how loud an IEM plays for a given amount of power, in dB/mW or dB/V. The KZ EDX Pro is rated at 112 dB/mW, so it gets loud on very little power.
- Impedance: the electrical resistance in ohms (Ω). Together with sensitivity it decides whether a source has enough power. Our guide to DACs and amps explains when that matters.
- Hiss: a soft noise in quiet passages, mostly with very sensitive IEMs. It comes from the source, not the IEM.
- Seal: the tip closing off your ear canal. Without a good seal the bass drops away. Our ear tips guide shows how to find the right size.
Reading reviews with these words
- Find out what the reviewer is used to. 'Lots of bass' from someone who wears neutral IEMs means something else than from a bass lover.
- Compare within one reviewer. Two IEMs from the same person, with the same rig and the same ears, tell you more than two scores from different sites.
- Check claims about sound against the graph. Bass, warmth, presence and sibilance should show up. Words about space won't.
- Then trust your own ears. Our guide to music for testing your IEMs shows how to compare fairly at home.
Products in this guide
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