The development of the Symphonia’s tweeter was spread over a three year period. I was always mesmerised by the sound of a true ribbon, especially Raal’s designs, but usually direct radiating ribbons lack the punch and dynamics of a high-frequency compression driver. On the other hand, no compression driver could ever deliver the detail, accuracy and bandwidth of a true ribbon transducer. So we began research on whether it was possible to combine the two approaches to get the best of both worlds.
A normal ribbon is not designed to operate at high acoustic pressures typically present at the throat of a horn. It soon became clear a special ribbon would need to be designed. After modification and experimentation on the Raal tweeter, we found the end result to more than meet our expectations. However, horn loading the ribbon still presented challenges. We were reluctant to use conventional solutions such as wave guides or directivity control apparatuses that would be inadequate for the task, so we endeavoured to find a new approach.
This lead us to design a horn flare that specifically loaded the ribbon as a true horn. Nevertheless, the line source emission characteristic of the ribbon made this extremely difficult. Diffraction is secondary sound emission, and takes place in geometric anomalies, transitions of geometry and changes in curvature. It’s very much audible and almost impossible to eliminate. In horns, diffraction is present at the horn termination for round horns. In rectangular horns the problem is more pronounced.