Accuton BD25-6-258 Diamond Tweeter

The Accuton BD25-6-258 is a diamond dome tweeter from Accuton's premium driver range, and like the rest of that family it is designed to reproduce the top octaves without contributing resonances of its own.

What separates one tweeter installation from another, once the driver itself is this good, is usually directivity rather than on-axis response. A dome radiates almost uniformly at low frequencies and progressively narrows as the wavelength approaches the size of the dome. The result is that the direct sound reaching the listener and the reflected sound reaching them a few milliseconds later have different tonal balances, and the ear integrates both. This is why two loudspeakers that measure identically on axis can sound quite different in the same room.

Practical consequences follow. The transition to the midrange driver should be placed where the two units have comparable directivity, otherwise the power response will show a step even when the on-axis curve looks flat. The baffle around the tweeter should be free of sharp edges and abrupt changes in width, since diffraction from those edges arrives slightly delayed and smears the image. A shallow waveguide or a generous roundover will do more for the perceived quality of the treble than almost any component substitution in the crossover.

Observe the manufacturer's minimum crossover frequency and use a filter steep enough to enforce it. A light, stiff dome has little mechanical damping in reserve, and low frequency content that a shallow filter lets through is the most common way a tweeter of this class is damaged.