What is a ribbon driver, and how does it differ from a cone or dome?

A ribbon driver is a planar transducer in which the diaphragm itself is the conductor. A thin, corrugated strip of aluminium — typically only a few micrometres thick, a fraction of the mass of even the lightest dome tweeter — is suspended in the gap of a powerful magnetic field. The audio current passes directly through the ribbon, and the resulting Lorentz force (F = B · I · L) drives the entire ribbon surface forward and backward as a single piece.

How it differs from a cone or dome

• Moving mass. A ribbon's moving mass is measured in milligrams — orders of magnitude below a 25 mm dome tweeter (~0.1 g) or a midrange cone (several grams). A cone or dome driver also has to move its voice coil, which is a significant part of its total moving mass; in a ribbon the conductor and the diaphragm are the same element, so there is no separate voice-coil mass to accelerate. The extraordinarily low Mms yields very high acceleration, so transients are reproduced with exceptional speed and "stop-on-a-dime" clarity.
• Distributed drive. The entire radiating surface is driven uniformly. There is no voice coil pushing a cone from its apex, so there is no cone breakup, no piston-mode flex, and no propagation delay across the diaphragm.
• No surround or spider. The ribbon is tensioned at its ends; there is no rubber surround or fabric spider to store and release energy. This removes the "surround resonance" coloration that every cone driver carries.
• Line-source directivity. A tall, narrow ribbon approximates a vertical line source, giving controlled vertical directivity and a much more gradual level drop with distance — closer to 3 dB per doubling of distance rather than 6 dB for a point source — within its near field.

The net effect is a driver that is faster, more transparent, and free of the mechanical signature that cones and domes impose on the signal.