The piano-string tensioning system: why Clarisys ribbons are tensioned like instrument strings

A ribbon is a thin, flexible conductor suspended in a magnetic gap. Left to itself, that foil would sag under its own weight, would not stay flat, and would have an uncontrolled mechanical resonance. Every ribbon speaker must deal with this. Most manufacturers simply clamp or glue the foil at its ends and accept whatever tension that produces. Clarisys does something different: it tensions the ribbon like a piano string, with an adjustable tensioning system, and no other ribbon manufacturer does this.

The analogy to piano strings

A piano string is a steel wire stretched across a frame at a precisely set tension. That tension determines three things: the pitch (the fundamental resonant frequency), the mechanical Q (how long the string rings), and the straightness of the string across its length. A piano is tuned by adjusting the tension of each string individually.

A Clarisys ribbon is governed by the same mechanics. The ribbon — pure aluminium for the midrange and treble sections, aluminium-Kapton composite for the bass section — is clamped at both ends into terminal blocks, and one of those blocks is part of an adjustable tensioning mechanism that lets the ribbon be set to a specific, measured tension. Like a piano string:

• the tension sets the ribbon's fundamental mechanical resonance — the frequency at which the ribbon wants to ring on its own;
• the tension sets the ribbon's mechanical Q — how quickly any stored energy decays;
• the tension keeps the ribbon flat and centred in the magnetic gap across its full length, so it never approaches the pole pieces.

Why this matters

A ribbon that is simply clamped is held at whatever tension the foil happened to be at the moment it was fixed. That tension is not measured or set to a reference, so the ribbon's mechanical resonance and its flatness are whatever results from that moment of clamping rather than a deliberate operating point.

With a tensioning system:

• Each ribbon is set to its correct operating point during manufacture, against a measured reference, so every panel behaves the same.
• The mechanical resonance is placed where it is harmless — out of the passband, or where the crossover attenuates it — rather than landing somewhere random in the midrange.
• The ribbon stays flat and centred, because the tension is actively maintained by the frame, not just by the foil's own stiffness.
• The ribbon can be re-tensioned in the field if it ever needs it, restoring the panel to spec without replacing it.

Why nobody else does it

The reason is straightforward: it is hard. It requires a frame rigid enough to hold a stable tension (which is why Clarisys uses CNC-machined aluminium), a tensioning mechanism at each terminal block, and a manufacturing process that sets and verifies tension per ribbon. It is cheaper to simply clamp the foil and ship it — and that is what the rest of the industry does.

The piano-string tensioning system is one of the reasons a Clarisys ribbon sounds the way it does, and one of the reasons it keeps sounding that way for decades rather than seasons. It is, as far as we know, unique to Clarisys.