You don't need fins on the cooling panel because it has far enough surface area. It doesn't even really need any airflow to work because it's oversized for the application anyway. The heat dissipates within about six inches from the plug, and by the edge of the plate the temperature is barely above ambient.

When using these horns outdoors, install snaps around the diameter of the plate and attach a flap of denim or plastic over the panels to shade them from direct sunlight.

To understand the differences between the prototype and production versions, see 12π basshorn subwoofer - the best yet!