Timbre in audio: what it is and how gear colors it

Same note, same level, different instrument

Play the A above middle C, 440 Hz, on a flute, a violin and a piano at the same loudness and nobody mistakes one for another. Timbre is the name for whatever still tells them apart once pitch and loudness match, so it covers every difference that is left.

Part of the answer is the spectrum. A pitched note is a fundamental plus overtones, and on most pitched instruments the overtones sit at whole-number multiples of the fundamental. Their relative strengths give each instrument its color. In its low register a clarinet, a pipe closed at the reed end, is strong in the odd-numbered harmonics and weak in the even ones. Instrument bodies and the human vocal tract add resonances of their own, set by their shape and not by the note being played, which lift whichever harmonics fall near them. In speech those peaks are called formants, and they are what tell one vowel from another.

The rest is time and noise. A plucked guitar string rises to full level almost at once and fades slowly, a struck cymbal starts instantly and rings for a long time, and a bowed note can swell in. Cut the first fraction of a second off recorded notes and many instruments become much harder to name. Breath in a flute, rosin on a bow and the rattle of snare wires tell you what is making the note as well.

The spectrum alone doesn't decide it. Filter a violin note until its spectrum matches a trumpet's on the same pitch and it still sounds like a violin. A playback chain can't turn one instrument into another. What it can change is the color: which harmonics come through louder, which resonances ride on top, and how cleanly each note starts and stops.

Where playback changes the color

Tonal balance comes first. Lift or cut a region and every harmonic that falls in it moves with it, on every instrument. A treble peak exaggerates the upper harmonics of strings and brass and the shimmer of cymbals, making them thin, steely or metallic, and a lift in the lower midrange thickens voices and brass. A sound signature describes that balance across the whole range; timbre is what it does to each instrument in turn.

Resonances come next. A cup, a shell, a cabinet wall or a diaphragm that rings at a frequency of its own adds that tone to every note that excites it, and keeps ringing for a moment after the note has stopped. The added tone sounds like the material of the product, which is why reviewers reach for words like plasticky, boxy, hollow or metallic.

Distortion adds harmonics that were never played. Good electronics keep it far below the music, and headphones and speakers produce much more. The harmonic distortion explainer covers which kinds are heard as richness and which as grit.

Speakers and in-ears with several drivers add one more variable: the handover from one driver to the next, often between different materials. The Diora Acoustics Chors 5 uses one material throughout, a ceramic-coated tweeter and two ceramic-coated woofers, and its review reasons that this should give every band a similar timbre. Because the same two woofers play the bass and the midrange, it hears the midrange share the bass's dynamic, snappy character.

Tonality and timbre in the reviews

Reviews on this site keep two words apart. Tonality is the balance of bass, mids and treble, and timbre is whether each instrument sounds like itself. The first feeds into the second, and a product can do well on almost everything else and still miss on timbre.

The Flare Audio E-PROTOTYPE is praised for its bass, separation and detail, and its review still calls timbre its weak point. It names two causes: mids that are "recessed yet peaky and unnatural", and a slightly plasticky color that it thinks likely comes from the material of the 3D-printed shell. The HIFIMAN RE2000 PRO Silver gets the opposite verdict on timbre: its review calls the treble realistic, with accurate timbre that doesn't sound metallic or plasticky, if a bit analytical. Both are ranked picks in the best IEMs guide.

Heard in sources and cables

Reviews here also hear timbre change further up the chain. The SMSL PS200, an $89 DAC, is described as adding a plasticky sound to strings and brass. Other reviews report cables moving it too, for better and for worse.

Differences like these are small next to a headphone's or a speaker's, which is why careful listening tests match levels before anything else: even a small level difference can sway which of two sources sounds better. A level-matched blind comparison such as the ABX test is the way to confirm one for yourself.

How to judge timbre by ear

Timbre is judged against memory, so use instruments you know from life: a piano, an acoustic guitar, strings, brass, a voice. Listen for the felt of a piano hammer and the steel of its strings, the rosin and the wooden body behind a violin, the breath at the start of a flute note and the chest in a low male voice. A color that belongs to none of them, a plastic sheen or a metallic ring on everything, belongs to the product.

Recordings you know well make the job easier, because you already carry a picture of how they should sound. Learning the bands helps too. The ear training game plays sine tones and sweeps and asks you to name the frequency, and once you can name frequencies it gets easier to say which part of the range a color lives in, whether it sounds thin, boxy or shouty.