The tweeter is the smallest driver in a speaker and handles only the top of the range — but it shapes a huge part of what you hear as detail, air and 'sparkle', and it's the driver most likely to sound harsh when done badly. It's also where manufacturers spend the most marketing energy, throwing around words like beryllium, ribbon and Air Motion Transformer with little explanation.
There are a lot of named tweeter technologies, but they fall into a handful of families. This guide walks through each one — what it is, how it tends to sound, and which brands in the TrueScale catalog are known for it — so the driver line on a spec sheet finally means something.
What a tweeter actually does
A tweeter reproduces high frequencies — typically everything above a crossover point around 2–3 kHz, where the speaker hands off from the mid-bass or midrange driver. To reproduce those fast, short waves cleanly, its diaphragm has to be very light and very stiff, and it's usually small (most are around 25 mm across).
Tweeters are named after the shape of that diaphragm (dome, ribbon, folded pleats), its material (silk, aluminium, beryllium, diamond) or its loading (horn, waveguide). Those three things are what the rest of this guide is about. If you're new to spec sheets in general, start with How to read a speaker spec sheet and come back here for the tweeter detail.
The soft dome — the smooth default
The most common tweeter is a soft dome: a small cap of fabric, silk or a coated textile, typically 25 mm. It's the sound of most hi-fi speakers because it's forgiving — smooth, easy on the ear and very hard to make sound harsh. The trade-off is that a soft dome can lose a little of the last-degree 'sparkle' and detail that stiffer materials extract from a recording.
It's the classic choice for a natural, non-fatiguing balance. ATC built its reputation on soft-dome treble (and a famous soft-dome midrange), and Triangle uses a silk dome across its entry Borea range.
Hard domes: metal, and the exotic tip
A hard dome uses a rigid material for more speed and extension, and a crisper sense of detail. The catch is 'breakup' — every stiff diaphragm has a resonant frequency where it stops moving as one piece and rings. The whole game is pushing that ringing far above the audible band (or damping it). Stiffer, lighter materials push it higher, which is the entire reason the exotic materials cost what they do:
- Aluminium / magnesium / titanium: the common metal domes — extended and detailed, well-behaved when the maker keeps the breakup out of the way. Monitor Audio is known for its gold-coloured C-CAM aluminium-magnesium domes.
- Beryllium: far lighter and stiffer than aluminium, pushing breakup very high for effortless, clean treble. A signature of Focal and of Paradigm's flagship Persona line.
- Diamond (and ceramic): the stiffest of all — the diamond dome is a hallmark of Bowers & Wilkins' top ranges, with its breakup pushed clean out of hearing.
Hard domes reward good recordings with more detail and can sound bright or edgy on bad ones — though that's usually the recording or the crossover talking, not the metal itself.
Ribbon and planar tweeters
Instead of a dome, a ribbon tweeter uses an ultra-thin strip of conductive film suspended in a magnetic field. Its moving mass is tiny, so it starts and stops almost instantly — the classic ribbon strengths are airy, delicate top-end detail and very wide horizontal dispersion. The trade-offs: a tall thin ribbon has narrow vertical dispersion (your ear height matters more), true ribbons are fragile and low in sensitivity, and they need a good transformer to match an amplifier.
Planar-magnetic tweeters use the same idea with the conductor printed onto a larger film, which is more robust and easier to drive — a middle ground between a true ribbon and a dome.
AMT — the Air Motion Transformer
An Air Motion Transformer (AMT) is a pleated, folded diaphragm that squeezes air out from between its folds like an accordion. Because it moves air faster than the diaphragm itself moves, it pushes far more air than its size suggests — giving the low-mass speed and detail of a ribbon with higher output and better robustness. Sonically it's prized for being fast, open and effortless in the top octaves.
ELAC's well-known JET tweeter is a folded-ribbon design in this family, and Monitor Audio uses an AMT (its MPD driver) in the higher Gold and Platinum ranges.
Horns and compression tweeters
A horn-loaded tweeter puts a flared horn (or a shallower waveguide) in front of the diaphragm. The horn acts as an acoustic amplifier and a director: it raises sensitivity dramatically and controls where the sound goes, so more of it reaches you and less bounces off walls and ceiling. That makes horns very efficient and dynamic — easy for a modest amplifier to play loud and lively.
Klipsch is the household name here, with its Tractrix horns and very high sensitivity; Fyne Audio places a compression tweeter at the throat of its IsoFlare point-source driver. A well-made horn is dynamic and easy to drive; a poorly made one can add a 'cupped-hands' coloration. If the appeal is the easy amplifier match, read Sensitivity and impedance: what amplifier you need.
Electrostatic and planar panels
Some speakers skip the discrete tweeter altogether. An electrostatic panel stretches an ultra-light charged film between two perforated plates and drives the whole treble (and often the midrange) with almost no moving mass — famous for see-through transparency and coherence. The costs are real: panels need mains power and space to breathe, throw a narrow beam, and are usually paired with a conventional woofer in a hybrid design.
MartinLogan is the best-known name in electrostatic hybrids. It's a different world from box speakers — worth hearing at least once.
Concentric drivers: the tweeter in the middle
A concentric (or coaxial) driver mounts the tweeter at the acoustic centre of the midrange cone, so both share one axis. The goal is a point source: the treble and midrange leave from the same spot, which tightens imaging and makes the sound less sensitive to exactly where you sit or stand. It's a design philosophy as much as a tweeter type — the tweeter itself is usually a dome.
KEF's Uni-Q is the best-known example, and Fyne Audio's IsoFlare and ELAC's concentric JET take the same point-source approach.
So does the tweeter type matter?
It sets tendencies, not destiny. A soft dome leans smooth and forgiving; metal, beryllium and diamond lean toward detail and extension; ribbons and AMTs toward air and speed; horns toward efficiency and dynamics. But a great crossover and cabinet matter more than the badge on the tweeter — a well-implemented soft dome will out-perform a carelessly used beryllium one. Treat the tweeter type as a hint about the speaker's character, then trust your ears.
Every TrueScale page lists the tweeter type and size in plain language. Pick a character you're curious about, browse the brands known for it, and put your shortlist side by side in TrueSpecs to compare the rest of the design around it.